geosciblog

Happy 374th Birthday to Nicolas Steno!

2012-01-11T13:23:00.000-05:00

The "layer cake" stratigraphy of the Colorado Plateau is a great place to see the three pioneering Geological Concepts of Nicolas Steno on display.

Superposition.

Original Horizontality.

And Lateral Continuity.

Hat tip to Polly, Geofriend on Facebook.

National Geographic Video - Electronic Magnetic Pulse

2012-01-01T12:07:00.000-05:00

Electronic Armageddon - whether by nature or by man - would be a nightmare for the advanced parts of the North American Continent.

Instead of wasting our time arguing over things we can't change, we need to have some sort of strategy in place to cope with such drastic events.

Fast Gold Concentration

2011-12-28T01:36:00.000-05:00

Offered here without any sort of endorsement. It just "popped up" during a YouTube search. May offer some comments, later.

Accretionary Wedge #41...

2011-12-12T10:34:00.001-05:00

Subject: the most memorable or significant geological event that you’ve directly experienced.

Excluding direct weather events, e.g., a tornado, dust storms (including a day-long dust storm waiting for the Space Shuttle to land at White Sands Missile Range), dust devils, and the remnants of a hurricane over the Eagle Mts.,...the most memorable geological event in my memory was the result of a weather event that happened a few miles away - A flash flood in New Mexico.

It was probably 1985, my wife and I went from El Paso to Hillsboro, New Mexico to visit a Labor Day weekend outdoor antique festival. During a previous year, I had a table selling beer collectibles ("breweriana") during one of the festivals and made a small profit. The first few outdoor antique festivals I attended were either on Memorial Day weekend or Labor Day weekend, I might have done the Memorial Day, it has been so long, I don't specifically remember.

At some point, the organizers decided to consolidate to the Labor Day weekend, to coincide with the Aspencade, enjoyed by bikers - you know the Harley-type bikers. There was one bar in town, when it was taken over by bikers, it made for some interesting encounters. The bikers were usually well-behaved during the daytime, as there was a healthy contingent of New Mexico State Police in the streets.

Anyway, after enjoying the festival and navigating the biker-filled bar for a beer, we decided to leave. Afternoon and evening summer time thunderstorms are not unusual in the area. I don't recall it raining in the town that day, but we were aware of storms in the mountains to the north and east of Hillsboro. After weaving through the mountains, we approached the last arroyo crossing before a long flat area that led to I-25. The arroyo was probably 4 or 5 miles east of Hillsboro.

Traffic began to stop and to our left, we could see that parallel to the road, the arroyo was filled with a "healthy" flash flood. As it was obvious that we weren't going anywhere for a while, I stopped the car and walked a couple of hundred yards down the road to get a better look at the flooded road and the upstream area. [As there weren't a huge number of cars, it was likely that the flood had only covered the road for maybe 15 to 20 minutes.] While watching, I observed one or two boulders - probably 3 feet in diameter - slowly tumbling in the muddy water. They didn't move far, but they did move. After a few minutes of "wow" - but lacking a camera - I decided to walk back to the car.

My wife and I had three choices: 1) Wait on the road until the flood subsided and the road was cleared; 2) Go back to Hillsboro and take the southern road from town - several tens of miles extra driving to get to I-25 or I-10 to the south; or 3) Or go back to the bar and have another beer or two with the bikers and then try the same road an hour or two later. We chose #3. By then, the road crossing had been cleaned of gravel and cobbles and we continued on our way, back to El Paso.

My uncle in Phoenix had warned me of flash floods well before I moved to El Paso, so if we had been there while the leading edge of the flood was within sight, but upstream from the road crossing, knowing the acceleration qualities of a Chevy Chevette, I probably would have opted to test the brakes and remain on the west bank of the arroyo, i.e., not try to "beat it out".

A Few Field Camp Field Trip Photos

2011-12-12T09:14:00.001-05:00

A few of these have been shot by friends during later trips, used because they are digital images rather than scanned slides or photos. Or because my camera demons prevented my photographing Arches National Park. They are not presented in the order in which they were visited.

As with other photos, these have been labeled for classroom use.

Field Camp Memories

2011-12-07T01:40:00.012-05:00

A Geologist friend commented on Facebook about the National Geographic show "Rock Stars", which I gather to be about engineers. She commented that it was about time that rocks made it to reality TV.

It brought to mind possibilities of an actual Geology-related reality TV series. If my UTEP Geology Field Camp of 1977 was typical, it would make for enough interesting stories for at least a short series - Geologists being the eccentric characters that they are. [But the problem is, unless the participants forget that there is a camera, they will alter their behavior, i.e., the incidents described below were spontaneous, not scripted or exaggerated for the camera.]

Late next May will mark the 35th anniversary of that summer, the first summer I spent in El Paso. Damn, time flies. Of note; the statutes of limitation have expired for any incidents described later. Sadly, I didn't keep up with the names of those non-UTEP students. One of which - from University of South Carolina - I gave a ride to as far as Atlanta afterward. 1,500 miles in 38 hours with a minimum of stops.

For those that have never experienced a Geology Field Camp, it is about learning and practicing different methods of Geologic Field Methods, mapping, measuring strikes and dips, measuring sections, estimated thickness of layers, etc.. Hours and hours outdoors. By our last full week, daytime temps were reaching 105 degrees.

Dr. Earl M. P. Lovejoy was a certifiable character. A big guy, he had a big, booming voice and a good sense of humor, including poking fun at himself. It was said that he died laughing at a student's joke during a field trip in 1980 (or so). A massive heart attack left him essentially dead by the time he hit the ground. He had a wealth of interesting and humorous stories. I miss those campfire conversations during the 10 day field trip.

An example of his sense of humor - during the 10 day field trip through the Four Corners States, someone found a bleached deer skull and tied it to the leading edge of the hood of one of the Chevy Suburbans. Someone else took a Sharpie and labeled it "Earl". Upon seeing it, Dr. Lovejoy pulled out his own Sharpie and added the initials "M.P." to the skull.

In no particular order of occurrence are some of the memories of that field camp and field trip:

Being beaten by the heat.

Spring semester 1977 was my first at UTEP. I had done well in Dr. Lovejoy's Geomorphology class, making an "A". He was expecting big things from me in field camp.

Having grown up in Georgia, I was used to "dripping sweat" during the summer time and compensating for that. I hated salt tablets and I didn't like Gatorade at the time. I made do with water (and beer). In the dry air of El Paso, one sweats without being aware of it, as evaporation keeps shirts dry - for the most part. After a week or so outdoors, I became fatigued and was not able to recover the lost energy. As I didn't complain, no one suggested salt tablets or Gatorade and I fell behind with the homework portion of the field camp assignments, turning in several of them late. I wound up with a "C" in the course without even understanding why. I just didn't have any energy. I never got fatigued enough to pass out or to "get stupid" (as I did with later episodes of dehydration/lack of electrolytes), thus my issues were "below the radar" and didn't get resolved.

Dr. Lovejoy's Death March.

During our first week of getting to know the El Paso Geology, one of our excursions was into the western side of the Franklin Mts., north of Tom Mays Park (and Trans-Mountain Road). I think most of our time was spent in the Ordovician, Pennsylvanian, and Permian sedimentary layers in the area, perhaps some of the Western Boundary Fault Zone was visited, also - as well as a probable discussion of the large landslide blocks in the area.

The problem was, it was a "two canteen" field trip - which I don't recall being announced and one canteen just wasn't enough. I don't recall plastic water bottles being as prevalent as they are now, so one WWII-era aluminum canteen was all I had. I wasn't the only one in this position. It seemed that the last mile of the "death march" was uphill to the truck in the heat of the afternoon. Again, no one collapsed, but it was one of those times when you could "see collapsing" from where you were. The student assistants may have had extra water, but it was one of those deals that - if you had to ask for water, you were going to catch hell about it, later. Rather, there would be much teasing about it.

Don't know about the origin of the "Death March" name, not to take away from the Bataan Death March, it was simply a humorous was of dealing with it. I don't know if it was a classmate of that time or someone earlier.

Don't ask me about "bugs".

Dr. Lovejoy's areas of expertise were Structural Geology, Geomorphology, Mapping, Landslides, and related things. Not paleontology. Not in the least. We learned to ask each other, one of the student assistants, or the assisting professor - "What is this fossil?" - out of ear shot of Dr. Lovejoy. If we lingered during a walk and he thought we were looking at fossils, he had something to say about that. If we had been in igneous and metamorphic rocks, he might have tolerated questions about minerals, but not "bugs".

Encounters with cicadas.

Most folks - along the way in their lives - have some sort of encounters with cicadas. In Georgia we have the "normal" Dog Days Cicadas that are active every July - September. Then as happens every 17 years (or 13 years - whatever) we have the "17 year cicadas" which are more incessant with their droning. As I didn't spend extensive time outdoors in El Paso during late-May/early June as I did in 1977, I don't know if the cicada "invasion" is the same every year or if 1977 was "special". I do remember cicadas landing on every vertical object, including standing persons and stadia rods. Nothing harmful about them, just annoying and their "singing" sounded like being at a jet airport. It may have just been that special time and place on the west side of the southern Franklin Mts..

Getting yelled at.

Rule Number 1 for Dr. Lovejoy's Field Camp. Everyone got yelled at along the way. Just part of the deal. Usually it was over our lack of plane table and alidade skills or something else that didn't meet with his approval. Usually the statement was; "This map is terrible. Why are you in Geology? Why aren't you in Sociology?"

A little background, as an undergrad at Georgia Southern, in the second quarter there - Spring of 1973, due to a late registration time, Historical Geology was closed out and I was forced to get Sociology as a class. Didn't want it, didn't need it, but most everything else was closed out. I found out later that though I was a declared Geology major, the Department Chair didn't yet know me and I should have raised hell about not getting the Historical Geology class. Too timid on my part. I suffered through the Sociology class and "partied" a bit too much and had a 59 average going into the final. I figured that some intense cramming would get me a grade in the 60s or 70s and I would at least pass. Somehow, despite the earnest study time, I made a 19 on the final. Out of that Freshman Sociology class of 35 people, there were 10 Ds and 7 Fs. The teacher was never in her office the next quarter and left the college thereafter. So instead of an A in Historical Geology, I got an F in Sociology my second quarter. Seriously damaged my GPA. Never thought that experience would come in handy, but...

When it came my time to be yelled at (with the standard line), I turned to Dr. Lovejoy and yelled back "Well, I flunked Sociology, what the hell was I supposed to do?" Reportedly, almost no one ever rendered Dr. Lovejoy speechless, but I did (and became sort of a folk hero for doing so). He shook his head and walked away, probably chuckling about it later.

Siestas.

The last full week of mapping in the El Paso area as at Mount Cerro de Cristo Rey, which straddles the Mexico/New Mexico border, just west of El Paso. It is a small Tertiary porphyritic andesite intrusion surrounded by intensely-deformed Cretaceous sedimentary rocks. There are several of these intrusions in the area, the UTEP campus is situated astride another one. Whether these were eroded magma chambers for overlying volcanoes is unknown, due to the effects of erosion.

Dr. Lovejoy had spent 13 years mapping the area and he had us checking for errors in his map. He was wise when he told us that "There is no such thing as a perfect Geologic map." I have found errors in several maps and I am sure that there are errors in mine. Anyway, by this time, daytime temps were reaching about 105 degrees.

When we would check in to pick up our bag lunch, we would usually take a small cooler with Gatorade and/or water (and perhaps a can of beer or two) and go back our chosen mapping area. Once there was some shade in the afternoon sun, we would often find a rock ledge under which to crawl to take a siesta. Either Dr. Lovejoy knew student behavior or someone tipped him off as he started going out looking for those taking a siesta - catching several of them - again they got yelled at. (BTW, I never got caught.)

Damned lechuguilla.

Lechuguilla is a member of the Agave genus and consists of essentially vertical spears vs. the usual radiating spears from a central stem of most yucca. they are called "Shin daggers" as they are usually fairly low to the ground and not as noticeable as other yuccas. They are also a hazard if you step over them and don't quite give them enough clearance, resulting in getting speared above your boot in the calf area.

The 10-day road trip.

Though we were expected to take some notes for a final exam, the 10-day road trip was a great relief from the field work just concluded. Being young, it wasn't much of an issue that the Chevy Suburbans (or whatever they were called) had no air-conditioning at the time, we just kept the windows down. I think there were 4 Suburbans and a supply truck. Somehow, those of us of the "hippy" type (think of "That 70's Show") wound up in the last Suburban, which came to be known as the "mass-wasted" group. We knew that for any stuff we did along the way, we had to be discrete.

We initially followed the Rio Grande Rift through New Mexico and into central Colorado, then went westward to Utah, then southward through the Four Corners area through eastern Arizona, then back through southern New Mexico. Stopped at a number of National Parks and Monuments along the way got some great photos - in most places. Besides the rift, we saw a good bit of the Basin and Range Province, the southern Rocky Mts., parts of the eastern Colorado Plateau, and more... [Photos will be in a separate post.]

The forest fire.

I think it was the 2nd day of the trip, when we stopped in a forested area to camp out in northern New Mexico, after we had set up the tents and assigned the "Supper team", several of us went for a walk in the woods with a beer and a "doobie". We made sure to ash the thing in an empty beer can as we knew the fire danger was high. After the proper period of relaxation, we returned to the camp and enjoyed the evening meal and after-dinner conversation. All was good as far as we knew.

The following morning, we packed up camp and left. Some hours later, we heard a radio report that there was a forest fire in the area in which we had camped. We knew we had been careful - in our "recreation", but there was that element of fear. Over the next several days, we kept hearing reports from the fire - with that nagging doubt always there.

Finally, on the third day of the fire, we heard a radio report that a motorcyclist had claimed responsibility for starting the fire. He was working on his bike when the engine backfired and set the tall grass afire, spreading from there. Talk about a collective sigh of relief - from something that we couldn't even talk about while it was happening.

So, what happened to that flaming car?

Somewhere on a mountain road in Colorado, we had taken a roadside break to observe the local Geology and the valley below. To our amazement, a Ford Galaxie came down the road with a small fire in the area of the rear license plate (where the gas inlet probably was). We didn't actually notice the flames until he was past us and there was no way to notify him of the problem. We watched him travel down the road into the town below, never seeing any sign of an explosion or larger fire. Weird.

That most painful hair-washing episode.

The third night of the field trip was spent in the vicinity of Spanish Peaks in southern Colorado. After 3 days in the vans, without a shower, the sight of a small creek at least offered us the opportunity to at least wash our hair, if nothing else. After putting shampoo in my hair, I dipped my head into the creek, not thinking about it being a snow-fed stream. Immediately my scalp was pounded with temperatures that must have been about 40 degrees F. It was exceedingly painful. To make matters worse, shampoo is not formulated to rinse at cold temperatures, which meant that rinsing too even longer than normal.

Five minutes after finishing, it was refreshing, but the transition from "ball-peen hammer" pounding to refreshing was not fun.

The "f__king babies" incident.

This one was not "my experience" but I was a witness... If memory serves me correctly, the driving chores were shared between the UTEP students and student assistants, with the lion's share of the driving of our Suburban being done by "Bob". We were somewhere in Colorado, I think. We were next to last - as usual - in the caravan. As this was before the days of cell phones and compact walkie talkies, we pretty much had to keep within sight of the vehicles ahead and behind us. As we had been driving for several hours with no significant breaks, except maybe to listen to a brief Geology lecture about an area, coming into a small town was generally expected to yield a gas/bathroom stop.

As we arrived at a "T" intersection and Bob waited for the chance to turn left, a line of 5 or 6 cars was approaching from the left. All of them appeared to shift to the right turn lane, so Bob began to pull out. One vehicle - a Dodge version of the Chevy Blazer (don't recall the vehicle name) did not go into the right turn lane, but continued on the street. Bob accidentally pulled in front of this vehicle, forcing the driver to "stop short" (but without locking the wheels). As Bob waved "sorry" to the driver, we noticed her - a very large woman - pound the steering wheel with disgust, but we assumed it was over.

We continued about 1/2 mile then turned into a gas station on the left. Bob pulled up to one of the pumps and one of the students set the pump handle, then all but Bob walked into the store. Bob turned and put his back to the vehicle window - to relax - as the offended driver was sliding to a stop in the gravel parking lot. She spotted Bob and marched over to the Suburban and started screeching about "those are my f__king babies in that f__king truck" (within earshot of the elementary school-aged kids). She repeated this line several times and was loud enough to capture the attention of most of the people in the store.

Other than apologizing several times, Bob covered his face with his hand and avoided arguing with her - which infuriated her even more. [We thought she was going to reach in the window and physically drag Bob out - she was big enough. And Bob was not a small guy.] After shouting for several minutes (or so it seemed), she stormed off, spinning her tires and scattering gravel, "chirping" the tires as she reached the street.

After she left, Bob walked into the store, approached Dr. Lovejoy and said "I suppose you were wondering what that was all about.", to which Dr. Lovejoy deadpanned "Yeah, I was curious.". After receiving an explanation, he issued the standard "Well, just be careful from hereon." - or something like that.

From then on, "f__king babies in a f__king truck" became a standing joke, for the rest of the road trip.

An interesting dichotomy.

At one of our camping stops, after dinner when we - the students - were seated around a campfire, several students from a very liberal San Francisco-area college asked if they could sit down at our fire, to which we affirmatively replied "Yeah, pull up a rock" or something like that. They were on a field trip to study American Indian art. To be hospitable, we offered them a beer and quietly asked if they wanted to "go for a short walk" - translated, to "share a smoke" with us, to which they affirmatively replied as one might expect.

Afterward, when we returned to the fire - the professors were at another fire, until later - they students commented on how they were warned not to "bring anything" on the field trip, lest they be sent home and flunk the class.

We immediately noticed - but did not comment on - this cultural contradiction. Students from a liberal San Francisco college were warned to "not bring anything", while nothing was said to us, we were just expected to be discrete (as previously described). Perhaps it was because the art students were more blatant on campus about their "consumption", but that is just a theory.

The field trip stops.

Without intensely reviewing a map and probably out-of-order, these are some of the places we visited: Spanish Peaks, CO; Dinosaur National Monument; Canyonlands National Park; Arches National Monument; Mesa Verde National Park; Four Corners Monument; Canyon de Chelly, AZ National Park, Black Canyon of the Gunnison,...there are probably other places currently not remembered. Getting a Geologic explanation at all of these stops was almost worth the price of the class itself.

Camera demons.

At the time of field camp, I had owned a Miranda Sensorex II 35 mm camera for about 2 1/2 years, with good results. It was a pretty good camera for its day, comparable with the Minolta SRT 100 series. I generally didn't carry it with me during mapping and hiking because of the extra weight, but on the field trip it was a necessity. As this was 1977, the only choice was to shoot multiple rolls of slides and then get them processed upon return to El Paso.

All seemed well the entire trip, but for some reason, somewhere between Canyonlands National Park and Mesa Verde National Park, the shutter jammed. It sounded normal, thus I had no idea of the problem at hand. For some reason, it seemed to fixed itself, with the "lost slides" primarily in the Arches National Monument and Four Corners Monument areas - in both areas, I had no slides returned from the lab, just black, unexposed strips of film. Thankfully, K-Mart (the cheapest way to get the slides done) didn't charge for those screwed up rolls.

[Because of the lost slides, when I had a summer job in Farmington two years later, I made a special trip to Arches and the same thing happened, except it didn't fix itself. I got hundreds of good slides from the Bisti Badlands of New Mexico, areas around Silverton, CO, and other places, but once I went back to Arches, my camera was toast for the rest of the summer job. I couldn't yet afford a "back-up camera".]

"It's the plague, it's the plague."

[Sorry, just had to do it.] When we made one of our last stops, at Canyon de Chelly National Park in eastern Arizona, the first night I chose to sleep out on the ground in my sleeping bag (which I and others had done several times). The next morning in the bathrooms, I noticed a flyer taped to the wall advising people not to pick up any "easily caught" squirrels, chipmunks, etc., as "the plague" was endemic to the area. After sleeping out on the ground - with the normal paranoia about rattlesnakes sliding into the warm sleeping bag - you can't imagine how thrilled I was to think about - sleeping on the ground, subject to plague-ridden fleas, ticks, etc.. The next night I slept in one of the Suburbans.

There are probably other memories, I may relate them as they return. If any readers have noteworthy stories, if the statutes of limitation have not expired, then perhaps change some of the names to "protect the guilty", hehe.

"Brinicles"

2011-11-25T07:43:00.002-05:00

Interesting formation of submarine (sub-ice sheet) ice "stalactites" that reach downward and freeze anything in their path on the shallow sea bottom. It might explain mortality-clustering (death assemblages) of certain fossils in the fossil record.

Always something new to observe and learn. Cool.

Not being a marine biologist, I wonder if all of the frozen organisms are dead or are some of them held in "suspended animation" until thawed?

One could also wonder about - in the past - how deep did these things go during protracted periods of cold, i.e., during Ice Ages?

Etowah River Tunnel Video

2011-11-20T12:01:00.002-05:00

About 35 years ago, my Dad and I visited an old mining-related tunnel on the Etowah River (probably in Dawson County). The tunnel itself was not part of a mine, but two different mining companies worked on the project to divert the river through a ridge, so as to mine the river bed for gold.

The "old timers" told them they would not find enough gold in the river bed to pay for the costs - and ultimately they were right. The first mining company started on the upstream side of the ridge, went halfway then went bankrupt. The second company came from the opposite end and met perfectly (horizontally), but there is a 30 inch drop "midway", as the second company's "half" didn't match vertically. That is the source of the "language" at about 2 minutes or so in the video. It is hard to imagine a "first timer" going over that drop without some sort of exclamation.

We were satisfied with visiting the entrance and panning gold from some nearby creeks.

Oh, did I mention it was in January? Riding in 40-degree rain, in an open-top Jeep, was not my idea of fun. We had gone there with a Dawsonville resident and his son (15 year-old with a learner's permit). My Dad and the other guy were in my Dad's truck and as I was the youngest adult in the group (at 21), I was "selected" to ride with the 15 year-old per Georgia law (regarding learner's permits). It wasn't raining on the trip to the tunnel, but it was on the way back. I enjoyed visiting the tunnel, but that ride in 40-degree rain was one of the reasons I hate cold weather. Even with a poncho, it was not fun.

Geologist Interruptus

2011-11-16T06:45:00.000-05:00

My bad, I have been busy with such things as job hunting and family issues - including a major cleanup of our garage and basement.

Will try to return to blogging, soon. Honest.

It's Earth Science Week - Day 4 - Park Photos

2011-10-12T23:50:00.001-04:00

Properly labeled geophotos can offer an interesting and useful teaching tools. In some cases, I have managed to convince friends to provide travel photos to cover areas not yet visited. [More meaningful commentary will be added later.]

Day 3 - It's Earth Science Week - Badlands and Hoodoos

2011-10-11T10:12:00.001-04:00

Just a few interesting landforms - large, medium, and small - courtesy of Mother Nature.

[Explanations and notes, later.]

Day 2 - It's Earth Science Week - Columnar Jointing in Basalt

2011-10-10T17:57:00.004-04:00

Will try to post each day of this week.

A fellow Geologist on Facebook posted the "what if" you could make pavers from columnar-jointed basalt. I posted these images on FB, so as to give casual readers an idea of what we were discussing - in some jest. The conclusion was (on my part) that basalt pavers would be neat, but because of access problems and logistics, it probably wouldn't work. The first 3 photos were from park areas, while the fourth is in a Wilderness Study area, 1 mile plus from any parking - even if it was legal.

This particular photo from Yellowstone was a scanned slide, taken by my Dad in the summer of 1980, while he and my Mom were on their last vacation together. He passed away that November.

A good friend went on a short vacation with his dad, brother, and son and got a number of photos of Devil's Tower in Wyoming.

The Aden Basalts - flood basalts from fissure eruptions - are located in southern Doña Ana County, New Mexico.

For those not familiar with columnar basalts, they usually form vertical, elongate polygons with 5 - 7 sides, during the cooling of surface and near-surface basalts in flows and volcano necks as you can see here. I seem to remember there being some columnar joints in some parts of the Palisades of the Hudson sill, but don't have any photos.

Day 1 - It's Earth Science Week - What Can You Do?

2011-10-09T15:27:00.000-04:00

One of the best ways to celebrate Earth Science Week (Oct. 9-15), is to show some appreciation to Earth Scientists.

Here are some ideas:

Take an Earth Scientist to lunch.
Be patient with our eccentric ways.
Understand that just because we may not have books on sale at Barnes & Noble, that doesn't mean that we aren't writers. We are sujbect to "writer's block" and when the "dam bursts", we may need to write down our thoughts before we lose them.
Be empathetic with us - as during decades of travel with others - we pass thousands of rock outcrops and other sites of interest, without stopping.
Just because we talk to ourselves, we are not necessarily crazy, we may be rehearsing a lecture or an explanation of a particular scientific issue.
It is OK if we say "I don't know". It doesn't mean we are not looking for an answer.
Part of being a scientist is observing things and seeking an explanation. Don't be surprised if we take an interest in things outside of our particular discipline.
Many of us have a never-ending "yearning to learn", so please don't be offended (or surprised) if we bring a textbook or small reference book with us during a casual lunch. We may be trying to reach a "learning plateau" on a particular subject, in case the opportunity arises to offer an educated opinion.

Other things may be added, as they come-to-mind.

Gold Fever Flows On

2011-10-07T10:44:00.002-04:00

From each one of the sluice videos, you can get some ideas, if you are interested in building your own.

Turbopan, hmmm.

A test of a highbanker, designed to speed up the removal of larger gravel.

Gold Grabber, another good idea.

More Low-Grade Gold Fever

2011-10-07T10:21:00.000-04:00

I have never owned or used a sluice box, but I am getting a "hankering" to build one. As a reminder, you have to remember to check on the status of the stream, so as not to get hammered for violations of regulations.

Also as I said previously, it is best to try to avoid excessive environmental damage. Try to restrict your digging to the active channel and eroded material along the margins (if old creek gravels are being eroded).

Still Nursing a Low-Grade Gold Fever

2011-10-07T10:13:00.001-04:00

Panning with Jayda, not your stereotypical gold miner. You can see in the early part of the video that this is not a casual operation. And as I am "environmentally aware", I am concerned about excessive disruption of streams - by digging into the banks. Digging in the channel itself (and in the eroded material from the banks) is not much different that what nature would do during a heavy storm.

But this appears to be the floor of an old mine, the environmental damage has already been done. Or maybe it is an active mine.

She knows what she is doing, I wish her luck in her endeavors. (I wonder where she is?)

What Was the Pleistocene? [Original Post Date: 10/25/05]

2011-10-05T10:05:00.000-04:00

Before we get to the issue of the Pleistocene re-wilding of North America, some may be wondering "just what exactly does "Pleistocene" mean?

"Pleistocene" refers to a specific interval of geologic time that is estimated to have lasted from 1.8 million years ago to 10 thousand years ago. It is best remembered as being the time of the last major Ice Age. Many scientists believe that "today's" warm climate is simply a natural rebound (or recovery) from the last Ice Age.

Referring to the accepted Geologic Time Scale (different versions may have slightly different age estimates), geologic time is divided into a hierarchy of time periods, based on different criteria. Most of the time boundaries are based on significant changes in the sedimentary rock and fossil record, as observed in 18th and 19th century Europe, where most of the present Geologic Time Scale was devised and defined. All of the time units, within the various categories, are of differing lengths.

The broadest time periods (at the top of the hierarchy) are "Eons", which cover hundreds of millions of years. We live in the Phanerozoic Eon, which began approximately 544 million years ago with the first widespread appearance of hard-shelled marine organisms.

Eons are divided into "Eras", which cover tens of millions of years. We live in the Cenozoic Era, which began approximately 66 million years ago with the end of the Mesozoic Era, when the dinosaurs became extinct.

Eras are divided into "Periods", which cover millions to tens of millions of years. The Cenozoic Era consists of the Tertiary Period (66 million years ago to 1.8 million years ago) and the Quaternary Period (1.8 million years ago to the present).

Periods are divided into "Epochs", which cover hundreds of thousands of years to millions of years. The Quaternary Period consists of the Pleistocene Epoch (1.8 million to 10 thousand years ago) and the Holocene (or Recent) Epoch (10 thousand years ago to present). The dividing "line" between the two epochs is the last major ice age.

As details of the geologic record become less distinct as we go back in time, the Epoch time classification is only used on a world-wide basis for the Cenozoic Era, i.e., the last 66 million years.

With the mass extinction at the end of the Mesozoic Era (and the end of the Cretaceous Period, too), approximately 66 million years ago, the niches and habitats of the world's ecosystems were "emptied out" of dinosaurs and other organisms. The mammal and bird survivors refilled these vacant niches and habitats with an "Adaptive Radiation", i.e., whereas the previous Mesozoic Era is known as the "Age of Reptiles", the Cenozoic Era is known as the "Age of Mammals".

With the natural global warming that ended the last Ice Age, human populations rapidly grew, cultures developed and humans migrated, in our case, most notably from Asia into North America. There was a significant extinction of large Pleistocene mammals in North America, attributed to human activities by some scientists, while others consider other possible causes (but not excluding the "human effect").

The article linked at the top of this post addresses the plans to introduce large African and Asian mammals (megafauna) to North America, to "replace" that which was lost in the last 10,000 years or so.

A Report on the State of the Geoblogosphere...

2011-10-05T09:03:00.001-04:00

is discussed on the German blog Geonetzwerk which presents;

..."data from an online survey with 78 participants and from analysis of more than 200 Earth science blogs.

Our survey shows that a majority of persons writing geoblogs are young, male, and academic. Most live in the USA and Europe. Collectively, their main motivation to blog is to share knowledge and to popularize the geosciences. Blogging is also seen as an opportunity to improve the authors’ writing skills, perform outreach, establish new contacts, and positively influence their careers. The rapid dissemination of news has been cited as an important advantage of the geoblogosphere."...

A little history:

..."The first geoscientific blogs were released in 2001 with “Green Gabbro” (Bentley, 2008) and in 2003 with “Andrew’s Geology Blog”. Building on the term “blogosphere”, blogging geoscientists soon established “geoblogosphere” as shorthand for the entirety of the geoblog community, including bloggers and readers.

In January 2010 the “Geoblogosphere News” aggregator by Huber et al. (2009) had tallied 265 blogs dealing with Earth sciences. This represents an increase in the size of the geoblogosphere of more than 100 % compared to the previous year."...

For what it is worth, my original blogging began in February 2005, though it was a hodgepodge of science, politics, culture, etc., so for that reason, it probably doesn't fit with the proper geoblog definitions of some.

There are some concerns - as there would usually be with a wide-open free-for-all atmosphere. Freedom can be messy.

..."Serious concerns about the credibility and trustworthiness of science blogs have been raised (Ashlin & Ladle, 2006). But no systematic approach to characterize the geoblogosphere has been carried out yet. Similarly, the geoblogging phenomenon has been incompletely documented. What is the geobloggers’ motivation to write? What is their background, both societally and scientifically? What are their information sources? How do they assess the benefits and disadvantages of blogging? What role will geoblogging play for the future working of the Earth sciences?

The first data on geoblogs were collected by Bentley (2008) who conducted a short online survey with 46 participants representing approximately 50 % of the geoblogosphere at that time (Geißler, 2009). Another geoblog-survey was started in August 2009 (female participants: n = 91) to investigate geoblogs as a resource and social support network for women geoscientists (Hannula et al., 2009a, 2009b; Jefferson et al., 2010). This survey included bloggers (n = 36) and blog readers.

With the rapid development of geoblogging, the authors extended and reissued the survey of Bentley (2008), supplemented by data from statistical and semantic analysis of more than 200 Earth science blogs. The study presented here is the first comprehensive attempt to characterize the geoblogosphere from the bloggers’ point of view."

Some other considerations:

..."Blogs have potential to be used as educational tools. In the past several years, several studies have shown that blogs support collaborative, participative learning (Agostini et al., 2009; Hall and Davison, 2007), increase student and teacher relationships, improve flexibility in teaching and learning (Ferdig and Trammell, 2004), and teach students the art of scientific argument (Moore, 2008). In the geosciences specifically, blogs can be powerful instruments to visualize geological phenomena, present annotated field trip guides, or accompany geo-educational projects like “Earth Learning Idea”, which supports teachers and teacher-trainers with Earth-related teaching ideas (King et al., 2008a, 2008b).

The fact that more than 78 % of the surveyed geobloggers write their blogs to acquaint laymen with geosciences suggests that geobloggers see blogging as being a form of geoscientific outreach work. One geoblogger wrote: “The whole goal of being a research scientist is to get your research out as quickly as possible to the widest possible audience. A well-known blog lets you do that very effectively. Our ideas reach people that they would never reach if they were only in our formal publications, and also act as a “gateway drug” to get people onto those publications where the ideas are worked out with full rigor.” Wilkins (2008) reached a similar conclusion; he argued that blogging should be understood as fundamentally outreach for science.

Meanwhile, public geoscientific institutions and societies focus more and more on blogging to increase their visibility to other geoscientists and to a wider public (e.g., AGU, 2010). This includes, for instance, blogs maintained by geological surveys, blogs about research expeditions, and conference blogs. The latter issue has been discussed by Bradley (2009) with the result that he evaluates conference blogs as more advantageous than not."...

Not as much as I should, I sometimes use this blog and my college blog as a teaching tool. I usually leave this blog for the more in-depth discussions or for things not discussed in class.

[For the sake of brevity, you should visit the original linked post for the "rest of the story. For what it is worth, I don't recall if I participated in the original survey or not. At that time, I had not "spun off" this (largely) non-political geoblog, so the politics of the original may have put some people off. We are what we are...]

A Bit More About Gold Sluicing

2011-09-29T08:31:00.000-04:00

A Renewed Interest in Gold Panning...

2011-09-29T01:55:00.001-04:00

is sweeping across America's "gold fields", i.e., places that have historically produced placer gold.

Here is a video from "Rock Raiders" - linked on The Blaze website - of all places. Part of the renewed interest is due to the increased cost of gold, another would probably be the higher unemployment rate leaves people with more time on their hands for such endeavors.

I have been out three times this summer with the Allatoona Gold Panners, visiting 2 different creeks in Cherokee County (or extreme North Cobb County), Ga.. I have found something in virtually ever pan, but it is mostly "flour gold", very small grains. The main idea is to have some fun - which I have. I also enjoy accumulating heavy minerals for use in lab classes or just to look through, under a microscope.

Here are a couple more videos:

From Arizona:

Here is an ad for a sluice system - sounds good, but one would need to check for local restrictions regarding the use of sluices. This Grizzly Sluice is cool, but it is a bit pricey - for the hobby miner. The MSRP is $547.00, at this website.

Here is a homemade sluice box:

Another accessory - a homemade "high banker", designed to quickly wash out the larger gravels:

American ingenuity, ya gotta love it! As a reminder, if there are any diamonds, they will be retained in the heavy mineral concentrate, so check it carefully.

The Okie Dokie Diamond [Original Post Date: 3/13/06]

2011-09-09T13:15:00.001-04:00

[Call it blog-post recycling or posting of "greatest hits", I am gradually transferring older posts from another blog, as time permits.]

Many people may not be aware of it, but Murfreesboro, Arkansas is the only place in the entire world where common people can pay a small fee and search for diamonds and keep everything that they find. All other diamond producing areas are owned/controlled by large corporations or governments.

From MSNBC News, an Oklahoma State Trooper, visiting the Crater of Diamonds State Park, near Murfreesboro, Arkansas, with his family - for the first time - found a 4.21 carat, canary yellow diamond, that is said to be flawless. Talk about beginner's luck!

The park is approximately 37 acres of ground that is periodically plowed. Visitors are allowed to crawl about on their hands and knees, that is how I found my small white diamond (.37 carats) on my first visit in 1973. There are other areas where people can dig and sieve sand and gravel in water to look for diamonds.

When I was there in the spring of 1978, a couple from Dallas was looking in the same area as I was looking. I left in the mid-afternoon to do some other things in the area. At dusk, I was parked along the road into town, looking for old beer cans in the woods when the Dallas couple recognized my truck and pulled over. They asked me to take a look at what they found and to tell them if it was a diamond. It was a 4 carat, brown diamond, not of gem quality, but with the classic octahedral diamond shape. I got to hold it and I was the first one to confirm that it was a diamond (the park office had closed for the day). I later saw a short newspaper article in a Dallas paper, wherein that diamond was valued at $4,000 because of its size, classic crystal shape, and it being an American diamond. And that was 1978.

The article mentioned that 84 diamonds have been found so far this year. When I was first there in 1973, they said about 250 diamonds per year were found by visitors. Most of them are not gem quality, but once in a while, someone finds a "blockbuster" of a diamond, worthy of faceting and mounting in jewelry. The three main colors at the Crater of Diamonds State Park are white (60%), brown (21%), and yellow (17%) - according to the linked site below. 383 diamonds were found in 2004 and 536 in 2005. The higher numbers than the 1970s may be partially a function of higher numbers of visitors and perhaps more serious methods of searching, perhaps more digging and less crawling.

As mentioned above, it is an Arkansas State Park, open to the public. The state of Arkansas has toyed with the idea of selling the property to mining company, but public pressure has so far preserved the status quo. I know that Libertarian/Conservative purists disapprove of government ownership of land, but this place is so unique, I think it should stay as a state park.

The first diamonds were found 100 years ago, when the area was a farm. The farmer, when dressing out chickens to eat, found shiny stones in their craws (not having teeth, some birds swallow small stones to aid in the digestion process and the shiny nature of the diamonds caught the eye of the chickens). The stones were identified as diamonds, but there were never enough to support a mining operation, so it became a tourist attraction. In 1972, it became a state park.

If you click on the Park link above, the middle-aged black man in the center "works" at the park. Every day the park is open, he is there to pay his fee and that is what he does all day, dig for diamonds. He was there the last time I visited the park in 1983 or 1984 and I talked to him briefly. He doesn't find a diamond every day, but he finds enough to scratch out a living. Some of his diamonds may be among the Arkansas diamonds for sale on this website.

If you ever go there, don't expect to find a diamond, but there is always a chance. There are other minerals of interest to kids, quartz crystals, amethyst, calcite, peridot, agate, conglomerate (a type of sandstone composed of rounded river pebbles) and other minerals. Just keep everything that might even look like a diamond<, and the rangers at the park are more than glad to look over what you have found and tell you "what's what".

Only in America

The Pleistocene Ice Ages [Original Post Date: 3/26/06]

2011-09-09T13:10:00.003-04:00

Currently, as defined by geologists, we live in the Cenozoic Era, Quaternary Period, and Holocene Epoch (since the last 10,000 years or so).

The previous epoch was the Pleistocene, which lasted from approximately 2 million years ago to 10,000 years ago. Before the Pleistocene Epoch was the Pliocene Epoch, which lasted from approximately 5 million to 2 million years ago.

Most people have a vision of the Pleistocene climate as being a single large Ice Age, when in reality there were several periods of glacial advance, separated by shorter interglacial periods, some of which were as warm or warmer than today's climate. The primary, attributed reasons for the fluctuations were variations in Earth orbit, Earth axial tilt, and variations in solar output. Some of these fluctuations exaggerate each other, while others moderate each other. Random events such as large volcanic eruptions may play a role, also. Evidence suggests that the global cooling began in the latter part of the Pliocene.

Some authors suggest that the emergence of the Isthmus of Panama (above Sea Level) during the Late Pliocene played a role in the cooling of the climate. Prior to the emergence of the isthmus, there was a narrow seaway that allowed the movement of warm waters from the Caribbean into the east Pacific. The closure of this seaway altered oceanic currents, while opening a land bridge that allowed the migrations of mammals between North and South America.

This series of slides is from a lecture on glaciers. Proceed forward to cover the Pleistocene. There have been previous periods of global glaciation, but those were before humans. Oxygen-18 isotopic data is one type of proxy data used to reconstruct paleoclimate history, including the Pleistocene data listed here in Wikipedia.

From youngest to oldest, as identified in North America, the Pleistocene glacial stages were:

Wisconsinan Glacial Stage
Sangamonian Interglacial
Illinoian Glacial Stage
Yarmouthian Interglacial
Kansan Glacial Stage
Aftonian Interglacial
Nebraskan Glacial Stage
Pre-Nebraskan

Slide 37 shows reconstructed temperature curves for the last billion years and the last 2 million in more detail. Slide 38 shows the maximum extent of the Pleistocene continental ice sheets. Slide 39 shows estimated sea level for the last 20,000 years. These particular slides are from the University of Portland.

After each glacial stage, the interglacial represented a period of natural global warming, a period of rebound. Since the end of the Wisconsinan Glacial Stage approximately 10,000 years ago, there have been several alternating shorter periods of warming and cooling.

Previous ice ages include:

A poorly-documented, possible ice age from 2.7 to 2.3 billion years ago, during the early Proterozoic Era.
The earliest, well-documented ice age was during the late Proterozoic Era, from approximately 800 million to 600 million years ago.
Late Ordovician Period 460 million to 430 million years ago.
Late Carboniferous Period to Early Permian Period 350 million years to 260 million years ago.

From this above-linked Wikipedia article:

..."The present ice age began 40 million years ago with the growth of an ice sheet in Antarctica, but intensified during the Pleistocene (starting around 3 million years ago) with the spread of ice sheets in the Northern Hemisphere. Since then, the world has seen cycles of glaciation with ice sheets advancing and retreating on 40,000 and 100,000 year time scales. The last glacial period ended about 10,000 years ago."

This Wikipedia link shows temperature trends during the last 5 million years.

The Pleistocene Epoch is the recent geologic past. If there were repeated periods of natural global cooling and global warming then, why are people so convinced that any and all unusual changes and variations are triggered by humans?

10.5 Apocalypse...Probably Not [Original Post Date: 5/22/06]

2011-09-09T13:05:00.000-04:00

As we proceed (lurch) towards 2012, it is possible that TV networks may rerun some of these recent-past disaster movies, especially during Sweeps Months. It is cheaper than creating new ones.

[Originally posted on 5/22/06 on another of my blogs. Modified slightly for today's "consumption".]

I don't know if any of you have checked in on the NBC 3-part disaster flick "10.5 Apocalypse" (Saturday, Sunday, and this upcoming Tuesday), where the Western U.S. goes to hell in a geologic handbasket. It has just enough science to be interesting and I am waiting to see how much of the Western U.S. is laid waste.

As for likelyhood of the envisioned chain-reaction of earthquakes, volcanic eruptions, sinkholes, etc..., it answer is...

Probably Not!

[Without my Physical Geology textbook here for refresher sake, I am going from memory.]

Plate Tectonics is driven by vertical convection currents in the Asthenosphere, a semi-molten layer beneath the rocky crust (the Lithosphere). So imagine conveyor belt systems upon which the continental plates ride "piggyback". Where there are Asthenospheric "upwhellings" of molten material, if these are upwhellings are linear, they split the overlying crust and push the plates apart. This is what happens beneath the Atlantic Ocean in regards to the Mid-Atlantic Ridge and also in the Eastern Pacific Ocean with the East Pacific Rise. So there are upwhellings of intense heat in the Mid-Atlantic Ocean and the East Pacific Ocean.

In the last 30 million years or so, the North American Plate has pushed over and distorted a portion of the East Pacific Rise. A portion of the East Pacific Rise is present North of the Mendocino Fracture Zone, off the coast of N. Calif., Oregon, Washington, and British Columbia. Here the Juan de Fuca Plate is sinking beneath the North American Plate. The sinking Juan de Fuca Plate is remelting and that is what causes the occasional NW U.S. earthquakes and the Cascade Volcano eruptions (including Mt. St. Helens).

South of the Mendocino Fracture Zone along the Pacific Coast to south of the southern tip of Baja California, the coastal area is dominated by the San Andreas Fault Zone, which is where a small portion of the Pacific Crustal Plate is sliding past the North American Plate. Inland from this area, the mantle upwhelling (mantle plume) is under the continent and may be responsible for the hot spot vulcanism (San Francisco volcanic field (Flagstaff area), the Long Valley Caldera in Calif., Yellowstone in Wyoming, and perhaps the Rio Grande Rift).

The Rio Grande Rift represents a thinning of the continental crust from the El Paso area northward into central Colorado. If the continent were to be rent asunder, per the movie, this would be a natural "weak spot", as the crust appears to be thinned, based on heat-flow data, seismic surveys, and the presence of young volcanic rocks from the Potrillo Volcanic Field in Southern New Mexico, northward along the river.

The "geophysics" of the areas under the continent are different enough that stresses probably are not going to be quickly transferred from one area to another.

Another issue brought forth in the movie was the "Accelerated Plate Movement" theory as proposed by the discredited geologist father of Kim Delaney's character, Dr. Samantha Hill. If the plate motions were to reverse themselves, I would be looking at what was going on along the Mid-Atlantic Ridge. Had one of the plates started to sink in relation to the other? That would signify the reversal from an upwhelling to a subduction zone, where one plate was sinking beneath another.

Mantle upwhellings have stopped before, but we presume it takes millions of years to transpire. And I don't recall any mention of a mantle plume beneath the Western U.S., in the movie. Dr. Samantha Hill's character makes mention of "Sub-Asthenosphere" earthquakes, but to my knowledge, the "plastic" nature of the Asthenosphere makes seismic wave propogation unlikely. The most damaging earthquakes, by conventional wisdom (and supported by data) originate in the upper 100 km (60 miles) of the crust.

The deepest earthquakes are associated with the deep Pacific Ocean subduction zones and some of them originate from as much as 700 kilometers below the surface. With these deepest of earthquakes, the seismic waves are associated with the sinking oceanic plate, which though partially-melted, still retains enough rigidity to transfer stresses.

So, in summary, there are an endless number of "what ifs" and things that geologists and geophysicists dream of seeing (for the sake of learning), in this movie, and while anything is possible, it ain't likely. Remember, it is Sweeps Month.

A Follow-up on the Previous Caldera Post [Original Post Date: 8/31/06]

2011-09-09T12:17:00.001-04:00

the ABC special did a pretty good job of explaining the basics.

In the case of the Yellowstone Caldera, it is thought to overlie a "mantle hotspot", as does Hawaii, where a particularly strong upwhelling brings heated magma towards the surface. As the magma body rises through the continental crust, it partially melts the crust, adding significant amounts of quartz, and other silica-rich minerals, such as muscovite mica and orthoclase feldspar.

From the above-linked USGS webpage:

"...Scientists infer that rhyolite lava flows as well as the caldera-forming ash-flow tuffs were fed from shallow magma chambers filled by the melting of rocks of the lower continental crust below Yellowstone. The heat needed to facilitate the melting process was supplied by the repeated injections of basalt magma from the mantle into the shallow crust."

As mentioned earlier, these silica-rich minerals make the magma more viscous. As the magma rises, the pressurized fluids (mostly mineral rich water) "wants to boil". Even though more silica-rich eruptions are the norm, from time to time, basalts can also erupt. The basalts are derived from the mantle below and when erupted, it is because the basalt has moved through the crust quickly enough not to melt much of the crust. [Note: The higher-temperature basalts can easily melt the silica-rich minerals,which crystalize at lower temperatures, than do the minerals in the basalts.]

These are large magma bodies, termed "batholiths" that become magma chambers for the overlying eruptions when they reach shallow-enough depths. More than 100 square miles is usually bulged by the rising magma.

When the buoyancy (sp.?) and the gas pressure of the magma overcomes the strength of the overlying rock, as depicted on the program last night, eruptions will break through in several places. These multiple eruptions taking place at the same time will produce gas-driven pyroclastic flows and partially drain the magma chamber. The magma chamber will then collapse inward, opening up a circular to round "ring fracture" system, which will provide more conduits for molten rock to reach the surface, likely triggering even more eruptions. Some of the eruptions may be restricted to the collapsed crater, while others will erupt outward.

Watching the pyroclastic flows from the smaller composite volcanoes gives an idea of the speed of these types of eruptions, but the caldera eruptions may be two to three orders of magnitude larger.

ABC Discovers Calderas [Original Post Date: 8/30/06]

2011-09-09T12:13:00.000-04:00

[Posted originally on another blog of mine.]

Or by another name "supervolcanoes". There are two active calderas or cauldron-type volcanoes (very large volcanoes with huge oval shaped craters) the lower 48 states, the Yellowstone Caldera and the Long Valley Caldera (eastern California). The oval crater for the Yellowstone Caldera measures approximately 36 miles X 48 miles and has erupted three times over the last 2 million years or so. The last major eruption was approximately 630,000 years ago.

The Cascade Volcanoes (Mount St. Helens, Mt. Rainier, Mt. Baker, etc.) are a smaller type of volcanoes, called composite volcanoes. Both types of volcanoes, calderas and composites are both capable of producing pyroclastic eruptions, which are the explosive eruptions which consist of gray clouds of superheated gases, volcanic ash, rock fragments, crystals, and pumice fragments, that are capable of moving across the countryside at speeds of up to 125 mph. Ancient pyroclastic flows (also called ash flows) have been traced from composite volcanoes to a distance of 60 miles and from calderas a distance of 100 miles. Once the ash flows begin their travel, a trapped layer of air beneath them serves as a cushion, allowing for less friction and greater travel distances.

These types of eruptions occur in composite and caldera eruptions because of the presence of silica (quartz) in the magmas. Quartz tends to increase the viscosity of magmas and as the magmas rise towards the surface, the quartz makes the magmas "want to freeze", while the trapped gases and liquids "want to boil". If the viscous magma plugs the volcano neck, pressure builds until the immovable object is overcome by the irresistable force, which results in an often catastrophic explosive eruption, a la Mount St. Helens, Mt. Pinatubo, El Chichon, Krakatau (1883), Mt. Vesuvius, etc....

As explosive as composite volcanoes are, calderas are much more so, as the quartz content is usually higher, i.e., the underlying magmas are generally similar to granite and the calderas are usually larger. Another caldera, which is approximately 1 million years old is the Valles Caldera, near Los Alamos, NM.

ABC is televising a special tonight [8/30/06] (9 PM EDT) called "The Last Days on Earth", which among other disasters, focuses on the damage that might be done to humanity by a large caldera eruption. The last major caldera eruption occurred about 74,000 years ago. That particular eruption of Mt. Toba in Indonesia reportedly put a major hurt on the DNA of early humans, i.e., there were mass casualties, apparently.

[As with typical Indonesian volcanoes, Mt. Toba was probably a large composite volcano, the explosive eruption of which triggered a caldera collapse. That is somewhat different from the caldera-type "supervolcano" mentioned in the first paragraph.]

Discovery of Evidence of the Oldest Land Plants in Argentina

2011-08-31T10:48:00.002-04:00

While looking up info on Liverworts,...

From a BBC article from October 2010:

Paleobotanists have recorded evidence of at least five different types of non-vascular plants - similar to Liverworts - in the form of cytospores from the Early/Middle Ordovician of Argentina.

From the article:

..."These spores, dating from between 473 and 471 million years ago, come from plants belonging to five different genera - groups of species.

"That shows plants had already begun to diversify, meaning they must have colonised land earlier than our dated samples," said Dr Rubinstein, who made the discovery with scientists at the National University of Cordoba, Argentina and the University of Liege, Belgium.

The researchers' best estimate is that the colonisation of land could have occurred during the early Ordovician period (488 to 472 million years ago) or even during the late Cambrian period (499 to 488 million years ago)."...

..."The previous record holder of the earliest known land plants were small liverwort cryptospores found in Saudi Arabia and the Czech Republic.

These were dated at 463 to 461 million years old."...

A bit more:

"The cryptospores from Argentina hint at where land plants originated.

"It most probably happened on Gondwana, as already demonstrated by previous discoveries, but very far, at least 5000km, from the Saudi Arabian and the Czech Republic, where previous earliest traces of land plants were found," said Dr Rubinstein.

As land plants matured, they evolved from liverworts into mosses, and then into plants known as hornworts and lycopods.

Then ferns appeared before seed plants, of which there are many species today, finally evolved."

For Today's Earthquake in Virginia...

2011-08-23T21:00:00.001-04:00

Accretionary Wedge #37 - Sexy Geology

2011-07-31T01:41:00.003-04:00

No, Geology is not a fetish for me. Sometimes an obsession, but not a fetish - there is a difference. Without going into any unnecessary detail, I will just list my favorite rock units, as this part of AW #37.

For photographic purposes, I related my "current love" for the Jurassic Navajo Sandstone, in my "What a Geologist Sees - Part 36". I haven't been in the outcrop area of the Navajo Sandstone for many years, but through some of my old 35 mm slides and digital photos given to me by friends - I have developed a great appreciation for the eolian cross-beds and the diverse settings in which the Navajo is exposed on the Colorado Plateau.

For fossil-collecting purposes, I would have to say that the Late Eocene limestones of the Georgia Coastal Plain and the Florida peninsula. Of greatest interest - to me - are the diverse array of irregular echinoids with a small, but nice assemblage of different scallops (Chlamys and Pectin sp.). On a smaller scale, there are also small comatulid crinoids and very small brachiopods at some of the localities. In the Savannah River area of Burke County, there are occurrences of the large oysters Ostrea gigantissima in the Griffins Landing Member of the Late Eocene Dry Branch Fm.

The widespread distribution of limestones (close to the Fall Line) and other evidence suggests that the Eocene, especially the Late Eocene was a time of warm temperatures, friendly to biodivesity. The Ocala Limestone in Florida is the dominant Late Eocene rock unit in Florida. Updip in Georgia, there are a number of different limestone units of interest, as well as the sandy Clinchfield Formation.

The first Late Eocene locality that I visited was the Tivola Limestone, in the Perry, Ga. area, in Houston County. This sand dollar was from that undergrad field trip, from the old Medusa Quarry, SE of Perry. This sand dollar is also found in the Tivola-equivalent at the Rich Hill quarry, just 2 miles from the Fall Line, NW of Macon.

Unless there have been some interpretational changes in the strat sections, the Sandersville Limestone is one of the youngest of the Late Eocene units in the Georgia Coastal Plain and the Periarchus quinquefarius was the last of the 3 (or 4) Periarchus species in Georgia. The Ocmulgee Fm. is a downdip equivalent of the Sandersville. Periarchus lyelli, from the uppermost part of the underlying Middle Eocene Lisbon Fm. and the Clinchfield is the first of these, followed by P. pileussinensis, then P. quinquefarius.

This smaller irregular echinoid is from near Leesburg, GA, in the old Starkville quarry. If memory serves me correctly, this is the equivalent to the limestone exposures at the northern end of Albany, near the "power dam" on the Flint River.

I traded for this specimen from the Florida peninsula. There are numerous other Late Eocene echinoids in my collection, and there are other Georgia collecting localities, some now inaccessible.

Presumably, it was the end-of-Eocene Chesapeake bolide impact that triggered a regional extinction event, which wiped out a number of the Late Eocene echinoid taxa or at least those in certain updip facies.

Yeah, I guess I am sort of in love with the Late Eocene of Ga. and Fla. Just don't tell my wife.

[Update: I seem to be having trouble with my Blogger account, it is giving me grief when I try to comment on my own post. So thanks to all that leave positive and useful comments. I am not ignoring you, the system just has a glitch.]

Accretionary Wedge #37 Seeking Posts on - Sexy Geology...

2011-07-30T22:12:00.000-04:00

August 26th is the deadline for your photos and stories of "Sexy Geology".

The host site - "Outside the Interzone" describes the desired type of story as: "...geology that makes your heart race, your pupils dilate. Rocks and exposures that make you feel woozy and warm. Structures and concepts that make your skin alternately sweaty and covered with goosebumps. Places you've visited, read about, or seen photos of that make you feel weak-kneed, and induce a pit in your stomach."

The original Accretionary Wedge site has this link on the subject.

This brings forth some interesting thoughts and I will try to have something, soon. Without getting "racy", that is. People think we are crazy enough as it is.

[Note: For what it is worth, to avoid any confusion, my regular "What a Geologist Sees" Parts 36 & 37 happen to chronologically coincide with Accretionary Wedge Posts #36 and #37. This is by shear accident.]

What a Geologist Sees - Part 36 - The Navajo Sandstone

2011-07-19T11:00:00.002-04:00

[A minor disclaimer - I am not 100% sure that this is the Jurassic Navajo Sandstone, there are other eolian sandstones in southern Utah, but I am going with the assumption that this is Navajo.]

This "wow" photo was taken earlier this summer by a couple from our church while they were on vacation in Colorado, Arizona, and Utah. They were kind enough to give me copies of their photos for educational use (and those will be captioned and attributed). As my budget and schedule doesn't permit such excursions, I am grateful for their photos - past and present. This is their first "digital trip", as past trips have been photographed on 35-mm film, necessitating scanning of prints or slides.

The above photo was taken along Utah Scenic Byway 12, somewhere near Zion National Park. This couple - Bob and Jenny - are very good about creating scrapbooks and logs of their travels and collecting all sort of info from the National, State, and local parks that they visit. But sometimes it is some of the "in-between" photos that are hard to locate (or else I can't find the same scenes photographed by other people - for ID purposes). I have several other great photos (for educational purposes) of the Navajo Sandstone.

This is another of their photos from this year, of "Checkerboard Mesa" in Zion National Park. An image of Checkerboard Mesa used to grace the cover of one of the Physical Geology lab manuals we used to use.

This photo from Upper Antelope Canyon (from a scanned negative) is from a previous western trip.

Though I haven't visited any outcrop areas of the Navajo Sandstone for years (decades), from my past photos and newer photos given to me, I would have to say that the Navajo Sandstone is my "favorite" sedimentary unit for photographic purposes. I don't know of any fossil-laden areas of the Navajo, it is the large-scale eolian cross-beds that make for great photographs and educational teaching tools.

[BTW, for fossil-collecting purposes, I would have to say that the Eocene Ocala Limestone (and similar-aged units in Georgia) is my favorite sedimentary unit.]

Accretionary Wedge #36...Stuff Left Behind, With Regrets

2011-07-16T23:56:00.008-04:00

What have you left behind in the field? What have you lost or what do you regret not having collected, including photographs? [Before going further, I would like to thank all of the participants.]

The first contributor, Evelyn Mervine recounts some fascinating field work in the Indian Ocean, then she goes on to relate what she regrets not bringing home - a baby goat or a baby camel from Oman. I wonder what U.S. Customs would have had to say about that? [I once used a large paper cup to catch a kangaroo rat (for a few minutes) in the Eagle Mts. of West Texas, but it wouldn't have acclimated to a caged existence.] If one lived on a farm, bringing home such "souvenirs" from the field might work, but not so sure in a two-bedroom apartment. I don't know whether goats and camels can be housebroken. Here is her post in its entirety.

From Ann's Musings on Geology, Ann muses on her extensive 35-mm photographic past and photos she didn't get. She recounts such issues as not wanting to expose her camera to adverse conditions, e.g., dust or rain or not wanting to carry the extra weight. [Been there, done that on both counts.] She also described the familiar college-student issues, such as the expense of film purchases and development costs. As I did, she chose slides as they were cheaper. Another constant issue with 35-mm film photography, you had to wait to know if you got one or more decent shots. Many times, once she found out that she didn't get a good photo, it was in a situation where there were no do-overs, no chance to revisit the site. [Another 35-mm hazard - forgetting to reel the film back into the cartridge before you open the back of the camera. In 1982, I lost all of my Wisconsin glacial features slides when I did this.] As I do, she now faces the dilemma over what to do about all of those slides and how to convert them. Hopefully this can be resolved in a satisfactory way, with a scanner of some type. [I have a scanner, but not the time.]

Dana Hunter also reminisces about the Photo Not Taken. Actually of the photos not taken when she lived in Arizona. The empty photo-box syndrome. I can attest that there is plenty of good geology to be photographed in all of Arizona, especially the northern half of the state...San Francisco Peaks, Page, Sunset Crater, Grand Canyon, Sedona, Jerome, Barringer Crater, Canyon de Chelly, Shiprock,...

Silver Fox at Looking for Detachment is the first to report on regretting leaving a geological/archeological item in the field. From her account, after being literally dropped-off by helicopter at a field site: ..."I found a large pink projectile point in the middle of the drainage I was walking down, a drainage that had obviously seen some flooding in the last 1 to 5 years. The point was possibly made of Ivanhoe "chert" (more precisely opalite or silicified tuff) from the Tosawihi Quarries of northern Nevada, a large series of rock quarries made by ancient to nearly present-day native Americans..." In following accepted archeological protocols, she left the point, intending to mark the locality on a map for later collecting by a "trained professional". For whatever reason, the info didn't get passed along and the point was probably washed further downslope with later weather events. [I once got a polite lecture from a friend about collecting a silicified limestone "hand tool" from a roadside site, but I was able to drive him to the site and point to the exact location, so he could relate it to his archeologist girlfriend, so no damage done.]

The next contribution comes from Egypt! Way cool. Selim Abdelrhman reports on the strange rocks of Wadi Elbattekh in Egypt. From his words: "OK, Wadi Elbattekh or وادي البطيخ my translation is “Watermelon Valley” it’s a Wadi filled with strange rock shape and very soft in touch. i think the origin of this rocks is still a mystery."...

From Casey at Gioscience comes regrets of not having collected more samples (and taken more photos) of ripple-marked sandstones during at 1998 GSA Southeastern Section fieldtrip in WV, a fieldtrip that included the legendary sedimentary petrologist Bob Folk. The ripple marks were in the Devonian Foreknobs Formation, part of the Catskill Delta.

The proprietor of GeologyMelange brings us his first geoblog post. The subject of regret was a past visit to part of Marble Canyon in Death Valley. Of most interest was an apparently un-mapped outcrop of deformed crinoid "hash". There were a sufficient number of photos taken, but no measurements were taken of the size or orientation of the outcrop and not enough samples were collected. But of even more interest were the cobbles of white marble, the origins of which were not discovered.

A photo of Christopher with a fault-breccia in Marble Canyon, just above the canyon sediments.

Ron Schott admitted not collecting enough samples from certain sites, taking enough notes, or taking enough photos. But his greatest regret was losing his first Estwing Rock Hammer, which he was given as part of his Colgate Univ. Field camp gear. It served him well in field camp, but when he visited Giant Mountain in the Adirondacks, the spirits of the mountain became incensed at his collection of samples of the Roaring Brook intrusion breccia. The spirits extracted their revenge by relieving him of his beloved hammer from its improvised rope belt. [I know the feeling. My Dad gave me a brand new Estwing Rock Hammer when I left home to go to UTEP for grad school. Despite having the handle wrapped with day-glow orange tape, I managed to lose it in the Eagle Mts., about a year and a half later.]

Jessica Ball (aka Tuff Cookie) has a similar story of losing a "first piece of field equipment", a little smaller, but still important. Somewhere in the area of Sugar Hollow in the Virginia Blue Ridge Mountains, her first hand lens slipped off its lanyard. From a separate adventure, she regrets not having kept her first pair of hiking boots, with partially-melted soles from an encounter with some of Kilauea's fresh lava flows. I am sure that those boots would have been good for some stories.

For my contributions, there are actually two different ones. In 1979, I had a summer job in the San Juan Basin of NW New Mexico, as part of a fossil recovery project, prior to the opening of an open-pit coal mine. Outside of our project area - on the road back to the dirt "highway", there was a reddish-colored outcrop of "clinker" material, i.e., baked Cretaceous shale with plant fossils. The baking was probably courtesy of an ancient, underground coal-seam fire. After driving by this site to - and from - my "days off", I decided to stop and have a look. I regret only picking up two specimens from this site, one (pictured) with an angiosperm leaf and a stem fragment and another with a piece of a stem. WHY DIDN'T I AT LEAST FILL A BUCKET FROM THIS SITE? I will never know.

The image is labeled for use in my classes.

The other under-collected site was the previous summer, when I was in the Eagle Mountains in West Texas. While surveying the area - as part of a planned thesis project, which was never finished, in favor of another a few years, later - amid the caldera breccias and ash flow tuffs, I found a chunk of siltstone, with some tiny impact craters. I regret not even doing a rough draft of the extent of this intra-caldera siltstone. It most likely was reworked, water-deposited ash, with roughly-defined bedding planes. The surface was marked by a few tiny impact craters, suggesting bombardment by explosion debris, while the upper surface was exposed, but soft and "plastic". Looking at cross-sectional view, there was evidence of other small impacts by broken crystals/rock fragments. I often include this in lab instructions to remind students that it is possible to find sedimentary rocks inside of volcanoes. SO WHY DIDN'T I PICK UP MORE CHUNKS OF SILTSTONE? [BTW, the place where I lost my Estwing rock hammer was a stop or two past the siltstone locality. Hmm, is there a connection?]

[Update: A couple more attendees to the party!]

Water and Rocks...At The Same Time reports on the discovery of a chevron fold in an outcrop of the Dolgeville Fault on a tributary of the Mohawk River, near Dolgeville, NY. The photo at left shows a portion of the fold. Several members of the field trip party picked up folded portions of (presumed siltstone), but Roy didn't want to add anymore clutter to the crowded van (be there, done that on a crowded field trip bus, it is hard to keep samples organized and under control). This was his 2nd chevron fold, the first he donated to his alma mater, SUNY Oneonta. Roy, you have my permission to collect the next chevron fold for yourself.

Dr. Ian at Hypo-center reports on some important items ALMOST LOST during field work in Lukmanier Pass region of Ticino, Switzerland years ago. After picking up a fair-sized sample of gneiss: ..."I was crossing a boulder field and noticed an interesting looking exposure up a steep face to my right. I put my notebook down on a rock, placed my map case on top of it, and my gneiss sample on that to stop it blowing away. I then headed up to the steep outcrop with my compass-clinometer thinking I could easily remember a couple of readings and rock details and return to record the information in my notebook."... After climbing upwards to check out more interesting metamorphics and record several more structural readings, he turned around to re-orient himself and return to collect his sample, notebook, and map case, when he realized - "Just damn! - all them boulders look the same!" (or something like that). More from Ian: ..."After an hour a mild panic started to set in. Had I just lost three weeks work down to my own stupidity? Since I knew that they had to be in the boulder field somewhere,..." He searched for two more hours. At the point of almost giving up hope, he decided to do two more passes through the boulder field, then he realized that the items of interest were a mere 10 meters away from him. But a sad postcript follows this reunification of geologist and field equipment... ..."After my degree, I went to Cardiff to do a Ph.D. and I told the metamorphic petrology lecturer about the wonderful metamorphic rocks at Lukmanierpass, including hornblende garbenschiefer and kyanite schists...I showed him the box of my rock samples that I had collected there. He asked if he could hang on to them for a while and I agreed. With the passing of my Ph.D. I completely forgot that I had lent him the rock samples. I moved on to Keele, and he moved on from Cardiff." So the location of the box of rocks is a mystery.

Well, us Geologists and our stories of "the ones that got away". Maybe some younger folks will learn something from our travails, lost samples, unphotographed localities, lost equipment, and regrets.

An Interesting Video...

2011-07-14T15:56:00.000-04:00

Golden Scientific Ages in Islam, from the blog GeoSelim from Abdelrhman Selim, a contributor to the ongoing Accretionary Wedge #36.

Interesting info and perspective.

From my more recent understanding of climate history, it seems that what we call the "Dark Ages" was a part of the Dark Ages Cold Period, a time of rather bad weather (and all that goes with it, such as poor crop production) in Europe.

The "Science" of Stained Glass

2011-07-14T10:21:00.001-04:00

Stained glass, as a hobby, was taught to me by a couple of friends about 30 years ago. I did a few panels and sold them in the El Paso area, then once I met my wife, I had other priorities.

I recently resurrected this hobby, in order to replace a clearlite that I was too cheap to "hire out" - to have done. I have plans for the other one, hopefully it will be finished in a few weeks.

The entire panel is 53" x 7", the longest panel I have ever done and the first in close to 25 years. It turned out as I wanted it. Random splashes of color, with interspersed sections of clear antique and glue chip.

The next one (to the left of the door) will be similar. I thought of doing random splashes of color with slightly curved lines, but I decided that it might be "too different", i.e., too much contrast.

If I like the second one more, I thought about swapping this one to the left side, but handling such a long panel is risky and the copper foil joints are not as strong as the lead ones, so maybe I will just leave well enough alone.

Here is a close-up of the top.

Here is a close-up of the bottom. I chose to make the lower 1 foot opaque, so the dog wouldn't be tempted to lean on it, if she saw something through the window (she has other windows for that purpose, to bark at squirrels, pedestrians walking their dogs, etc.). She has actually broken through two smaller window panes to go chase squirrels. I hope she has forgotten that "skill".

It may be a bit of stretch, but one could make a comparison of learning how to properly cut glass (and how to clean up all of the tiny flakes and slivers) to the practice of science principles. I will probably leave those details to a later discussion. Hope you enjoy the photos.

[Actually, I have included slivers of polished agate in some small, experimental glass panels before. Might do that again.]

Tennessee Landslide

2011-07-10T09:04:00.003-04:00

No, this is not a new one, but it is a "geo-favorite" of mine as I have driven this section of U.S. Hwy 64, along the Ocoee River several times. Though this is a small landslide, the "carrying-along" of the trees is impressive to students.

The newsmen discuss making the video:

Of importance is the way the gentleman in the red shirt discusses the sounds that preceded the slide. Listen to nature!

Part II, from YouTube user "wdef":

Tennessee Geologist Vanessa Bateman was responsible for clearing the area of TDOT workers, journalists, etc.. To review, there had been a small landslide and the various observers had gathered to look and the TDOT workers had gathered to start cleaning the road. Apparently, Vanessa arrived, looked and listened to the mountain-side and decided "this ain't over, yet." and ordered people and equipment out of the area. Thankfully, they listened.

To add a little local geo-info, this area is in SE Tennessee and the rocks here are mostly slates and other low-grade metamorphics of Precambrian age (if memory serves me correctly). As you can see, many of the fractures/rock-cleavage planes are dipping towards the highway, so after heavy rains, this area is always going to be susceptible to landslide events.

In closing, this is a geo-favorite because (in no particular order):

1) It shows nature in action.
2) It is "local" (in terms of Southern Appalachians).
3) No one got hurt.
4) A Geologist was the hero. Sometimes we don't get no respect from engineers - been there, done that - on a less dramatic scale.

Announcing Accretionary Wedge #36

2011-07-02T07:21:00.000-04:00

The subject of this Accretionary Wedge is:

"What do you regret leaving behind at a geological locality?"

In other words, what samples, specimens, or even photographs do you regret "not getting enough of"?

One mindset is that we should only pick up a few of whatever the item-of-interest is and leave some for others, but there are other considerations. Sometimes outcrops get destroyed by construction...I have had that happen several times. And weathering and erosion are always "attacking" fossils, minerals, etc..

So go back and revive those old memories of places that you may never have a chance to visit again. It may inspire another geologist of two to pick up a few more specimens at a site - which of course can be shared along the way with other geologists or students if you find yourself in a classroom. A well-timed gift to a student may be the genesis of a new scientist.

Ya'll have at it. Please send your submissions by July 16th or so. So that I might assemble and post the results by the following Monday.

My Head in the Clouds

2011-05-27T10:45:00.000-04:00

Characteristics of a Scientist include...

Observation. Imagination. A sense of wonder. An understanding that the Learning Curve never ends. A hunger to learn more. A willingness to look up as well as down.

One of my side interests is the observation and photography of clouds.

"Atmospheric Optics" is an excellent site for info on clouds and other atmospheric phenomena. There are others worthy of visits as you embark upon your self-taught journey into Nephology - the study of clouds and cloud formation. Some of the phenomena show on Atmospheric Optics are things I will probably never see first hand, but there are others that - having been shown them - I will certainly be watching for.

This beautiful cloud was photographed in the early 1990s, looking eastward from the eastern margin of El Paso. I would guess that the horizontal distance to the area below the center of the cloud would be about 20 - 30 miles. My only regret is that I didn't jump into my truck and travel a bit further east to get a clearer view of the rest of the eastern sky.

Learning about clouds is truly a challenge, as there often is an element of interpretation as to what name to apply. There are also clouds that are combinations of two or more types.

Another challenge is the clouds are often in a constant state of flux as well as lateral movement. Particular structures may only exist for a few seconds to minutes. Or wind conditions may be blowing clouds away from you as you wish to gain a better view for photographic purposes. I once spent about 20 minutes driving through the northern Atlanta "burbs" chasing some clouds as they were blown westward. If not for traffic lights and traffic, itself, I might have made it for a better view. But they just got progressively further away from me the harder I tried.

When I rarely travel by air, I prefer to sit by a window with a camera to pass the time. This image is actually from a scanned slide, originally taken by my Dad in the late 1950s/early 1960s. It took a bit of time on Photoshop to remove dust spots and scratches.

As time permits, I will try to post a few more photos of my favorite clouds.

Accretionary Wedge #34 - Weird Geology

2011-05-22T19:06:00.002-04:00

[I thought about writing about my adventures on the Georgia Coastal Plain, near the northern end of Lake Blackshear and the inability to correlate Tertiary sedimentary units from one side of Turkey Creek to the other, but that is for another story...]

Instead, the photos here are from a November 2007 visit to the northern shores of Lake Lanier, near Laurel Park, in Hall County, Georgia. At the time, the area was in the grips of a multi-year drought. I went to the park as the severely-declined lake surface had exposed part of the old grandstands for Looper Speedway, an old dirt track covered for the last 50+ years by Lake Lanier. After photographing the old concrete-slab grandstands, I began to walk about a 1/4 mile or so in the opposite direction, to the north and west along the lake shore, observing the "wave cut bench" cut into the heavily weathered - partially saprolitized - metamorphic rocks (presumably old amphibolites).

In the distal portion of my shoreline "walkabout", the remnant foliation looked pretty "normal" for the Georgia Piedmont, i.e., not much distortion (as shown below). Saprolite composes not only the wave-cut bench, but also the small wave-cut cliff. In some places, the wave-cut cliff is composed of paleogravels from the nearby Chattahoochee River. I dug some of the sand - from the eroded gravels - from recesses in the clayey saprolite, panned it, and found a few grains of gold.

This second photo is looking NW along the shoreline, away from Laurel Park, looking to the left in relation to the previous photo.

Continuing southeast - back towards the Laurel Park boat landing - the geology began to get a bit "weird", with the appearance of large blobs of a "mashed" quartz/k-spar pegmatite.

A closeup of one of the pegmatite "blobs".

An axial view of the elongate blob shown in the third photo. This pod is about 2 - 3 feet at its widest point.

This crude "flower structure" seems to suggest that the pegmatite was squeezed in a manner similar to what one might see when a tube of toothpaste has been squeezed too hard.

A slightly different view of the same structure. There is a dramatic change in the rock "fabric" (foliation) with the fabric in the foreground at an approximate 90 degree angle to that shown to the left (behind) the "flower structure". It would have been interesting to see this structure when the rocks were fresh, to better understand what sort of deformation we have here.

It will require some time perusing geologic maps to determine to which metamorphic unit these rocks belong.

With the recovery from the drought, the lake has returned to "full pool" conditions and these exposures are now under several feet of water. The last time these areas were exposed was during an extended drought in the early 1980s. I should have returned for a few dozen more photos while this area was exposed, but...

Accretionary Wedge #33 - Xeriscaping

2011-04-14T08:15:00.001-04:00

Xeriscaping, it accomplishes several things for Geologists. Aside from saving water, it gives us a way of putting our "yard rocks" to good use, while doing something with that patch of yard that is in the shade, i.e., where the grass will never grow well, short of using massive amounts of fertilizer.

The following photos are from an ongoing project, which was begun in 2002 and proceeds when time and money allow. Or when I can pick up some more rocks during field trips, roadcut stops, etc.. [I hate having to pay for rocks, but I have to sometimes to get the variety that I want. I don't have a ready source where I can dig my own river gravels, volcanic cinders, gray slate, etc..]

Some family members would probably call these "unfinished projects", I would prefer to call them "in-progress".

The rocks and other materials come from a wide variety of sources. The flat stones adjacent to the driveway and the walkway in the first photo are from rock walls at the "old homeplace" (that was torn down a few years ago). Other flat stones from those rocks walls "live on" in rock walls in the current back yard.

The bricks are from three different sources. The first batch is composed of old hand-made bricks from the late 1850s, from the two-story brick home that my great, great-grandfather, purchased after the Civil War. The home itself burned in the mid-1960s, but scattered bricks were to be found until the site was developed into a strip mall and theater complex.

I made a few trips over across the Chattahoochee River to gather a few dozen bricks at a time in the 1970s through the early 1990s. [My great, great grandfather was reputed to have buried gold coins in jars as he didn't trust banks. One story was that when he suffered a stroke in 1888, prior to his death, he wasn't able to tell the family where he buried the jars. I didn't find any of them, myself. I wonder how many gold coins are buried under those asphalt parking lots?]

The next batch of bricks are from a former family brick company in the center of our town, presumably from the 1920s or so. Despite being of fair to poor quality, several buildings were built using these bricks and due to renewal projects, several of these buildings have been torn down, again providing a source for a few dozen bricks.

More recent additions include these broken slabs of "Baltic Brown Granite", collected from around a dumpster. In the storage area that a friend uses, a small granite countertop company had closed and had dumped dozens of chunks of waste rock around the dumpster, so being a kind, benevolent Geologist, I gave these chunks of porphyritic, orbicular granite a home.

The bricks used in edging this project were from a brick walkway at the "old homeplace".

Current photo of the "Baltic Brown project" shows soil that has washed in due to recent heavy rains. Will have to figure out how to resolve this. Also, in the second photo, you can see how moss has colonized the interstices between the flat stones. In addition, the moss prefers the old, handmade 1850's bricks versus the newer ones.

This photo shows some of the rock walls in the back yard, the one on the left encircles a wildflower garden. Most of these flat stones were retrieved from the old homeplace.

I picked up this irregular slab of granite from a granite-finishing place near Elberton, GA. Some family members at first thought it looked like a headstone, but have gotten used to its presence.

A little redneck Geologist Feng Shui near the street.

Another rock wall encircling my Liriope bed, this happens to be under an old ornamental cherry tree and it "hosts" yellow morel mushrooms, suitable for cooking and enjoyment.

These thin sandstone slabs are among the few stones that I have purchased. I wanted to have a small flower bed in the "middle" of the yard and I didn't have enough of the other flat stones.

There are other small rock walls encircling other flower beds, etc. and I am always on the lookout for sources of flat stones, large (20 - 30 lbs. or so) and small.

If we have to move to a smaller home, I am willing to leave most of this behind, though I will ask the next owners if they plan to keep them. If they answer that they plan to get rid of any or all of it, I will find a way to move it somewhere else.

I hope that I may have inspired some other Geologists to put their "yard rocks" to good use. Though some of them are too big or ugly to be indoors, we can still show them the respect and affection that they deserve, after we removed them from their original homes.

What Would Happen if an Asteroid,,,

2011-04-07T03:34:00.000-04:00

300 miles in diameter hit the Earth? The slate would be "wiped clean", so to speak. Scientists think it may have happened 4 billion years ago.

If we had a few days/hours advance warning, all that could be done would be to get your affairs in order, vis-à-vis with personal relationships, etc.. When it became obvious that it wouldn't be a near-miss, you might consider cashing in your life insurance policies as well and throwing a party to "end all parties", i.e., one that would never be topped. I am sure beforehand it would spawn all sorts of doomsday "gallows humor" as we attempted to cope with the thought of the finality of this event.

Kind of spooky, but it is what it is. "Nature bats last."

If I had the Time and Money...Part 1

2011-03-26T10:12:00.002-04:00

One of the places I would like to visit is the San Francisco Volcanic Field, North and Northwest of Flagstaff, Arizona. Especially Sunset Crater.

Having passed by the area each time I visited the Grand Canyon, I knew a little about the field, that it was composed of a combination of composite volcanoes and cinder cones and that it was relatively young, but I knew little else.

While surfing the Geoblogosphere, I happened across the short, photographic post at Geologic Froth, on Red Mountain, which is a dissected cinder cone in the San Franciso Volcanic Field. The photos showed what appear to be bedded, volcaniclastic sediments, including cinders preserved in some canyons within the Red Mountain area.

Following up, I found this link with a more detailed USGS report.

According to the USGS Fact Sheet:

"Red Mountain is one of several hundred cinder cones within a swath of volcanic landscape that extends 50 miles eastward from Williams, Arizona, through Flagstaff to the canyon of the Little Colorado River."...

..."The San Francisco Volcanic Field has been active for about 6 million years, and Red Mountain is roughly 740,000 years old."...

Those of us within the realm of Geology usually think in terms of deep time and we understand that anything volcanic less than 1 million years old (per current interpretations) is young and could be susceptible to a reoccurance.

Thinking as a Geologist, consider the scientific and tourism value of a new cinder cone near Sunset Crater. Cinder cones and shield volcanoes generally cause a bit less mayhem than pyroclastic eruptions and/or lahar
flows from stratovolcanoes.

That just begins a "laundry list" of places I would like to visit/re-visit in the Grand Canyon State, partially because digital cameras were not available last time. The only places I have been since having a digital camera have been the Grand Canyon and the Sedona area on a brief, pass-through trip.

"Use It or Lose It" Political Mindset

2011-03-21T10:01:00.000-04:00

[Editor's note: I don't like to inject politics into this blog, but as the government chooses to inject politics into science and the marketplace, it is necessary in this case.]

In recent years, when gasoline and crude oil prices have risen sharply (due to more than one reason - including the lack of a firm, coherent national energy policy), some politicians have attempted to scapegoat the oil (and gas) companies by suggesting that oil companies are "sitting on X million acres of leased Federal Land", inferring to the public that American oil and gas firms are sitting on millions of acres of proven oil/gas resources and all that is necessary is for the firms to drill.

They further infer that the companies are not drilling in order to "jack up" crude prices to benefit themselves (and also deliberately under-utilizing refinery capacity for the same reason). The refinery issue is for another time.

From the mouths of at least some of these politicians (and the compliant MSM), this inference is to; 1) Deflect responsibility away from the Federal Government's policies; and 2) Perhaps plant a seed of justification in any future attempt to nationalize American oil and gas firms (in a cited Emergency, by suggesting that said firms were not doing everything they could to bring down prices by increasing production).

What they do not say is that there is already a "use it or lose it" clause in each Federal Lease.

From this particular source, an API Fact Sheet:

"If companies do not produce oil or gas on leases then the leases must be returned to the government.

•Companies are required under government leasing regulations to develop a lease expeditiously (between five- and 10-year terms, depending on the area) or return it to the government. In general, leases not producing by the end of their term are relinquished back to the government,..."

There are already incentives to produce from these properties, aside from market prices:

"•In addition, companies already pay a rental fee during the pre-production phase of development. Rental fees on leases can now exceed $100,000 annually on some leases. Rental rates increase in the later years of the lease to encourage diligent development.

•Companies invest billions of dollars to acquire and maintain their leases. In addition to rental payments during the pre-production period, companies also pay a bonus bid to acquire leases.

Oil companies holding leases are in the business of finding and producing oil and natural gas, but a lease is only the first step."

Before drilling can commence, there have to be permits issued. The permitting process can be held up by bureaucratic inefficiencies and/or by deliberate, agenda-driven delays:

"•In many cases, the administration itself is preventing the industry from developing leases by not issuing permits to drill on them. Companies cannot develop existing leases without drilling permits."

When Federal lands go "up for lease", it is in a competitive atmosphere, in which companies may believe that if they don't bid, they may be left out. Sometimes, due to particular tax laws, companies may feel compelled to spend the money on leases that might pay out in the future, rather than have the money lost to taxation.

"Exploratory drilling occurs only when the geological formation shows potential, which is often unknown until after the lease has been purchased and studied.

•When companies bid on a lease, there may be minimal information available to evaluate its resource potential. Because of the competitive nature of the domestic oil and gas industry, companies are willing to risk capital to capture leases while speculating on the resource potential these leases may contain.

•Before drilling an exploratory well, companies may conduct seismic studies which require permitting to determine if commercial quantities of hydrocarbons are likely. If they believe commercial quantities exist, they will seek another permit for an exploratory well. Developing a lease can be a complicated process. Detailed planning, permitting timetables and regulatory and safety requirements must be met before development can occur."...

As drilling and completion costs can easily run into the millions, especially in offshore wells, it is cheaper to use seismic surveys to "narrow down" the areas to be targeted. But even expensive seismic surveys prove nothing. They just provide some more evidence of where oil and/or gas MIGHT BE. Again, the seismic permitting process is subject to the same delays as the drilling permitting process.

Another issue not considered in the article, some of those companies might have leases on State or private lands to consider at the same time. The offshore parcels, while much more expensive to drill and complete, hold the hopes of "the next new large discovery", i.e., the next new giant oil/gas field. The conventional wisdom is that "all" of the large/giant onshore oil/gas fields have already been discovered, but if money is tight, onshore efforts might be more attractive though the payoff will be smaller.

Back to the API Fact Sheet:

"Production will only occur if resources are found, and found in commercial quantities.

•Not all leases contain hydrocarbons. Accumulations of natural gas and oil occur on only a small number of leases. It is not uncommon for a company to spend $100 million to drill a well and find no oil or gas. Companies drill more wells that have no oil or gas than wells that actually do.

•Not all leases will have enough hydrocarbons present to make development commercially viable."

Regardless of how much money is spent on geologic studies, geophysical studies, hunches, etc., the only way to ultimately KNOW what is "down there" - is to drill.

"In the OCS deepwater, costs can exceed $2 billion for a platform alone. Some factors a company will consider include:

Amount of recoverable hydrocarbons;
Technology restrictions; and
Availability of critical infrastructure needed to bring hydrocarbons to market.

Some leases go undrilled because their potential can be determined by exploratory wells drilled by the company at nearby leases.

•Given the relatively small size of an OCS lease, and the fact that many geologic formations and trends can cover a large geographical area, companies often bid on several contiguous leases in a geographical area it believes will have underlying oil and natural gas resources. A strategically placed exploratory well on a single lease may give the company enough data to determine the hydrocarbon potential of many leases."

As for the infrastructure issues, that applies to onshore drilling, too. At least once, Bakken Fm. wells have been "shut in" because of a lack of a pipeline or insufficient capacity in a nearby pipeline.

[When work permits, I may come back and refine this a bit more.]

Five Themes of Geography

2011-03-15T09:31:00.002-04:00

From the above-linked website:

Explanation of the Five Themes of Geography

"The five themes of geography were created in 1984 by the National Council for Geographic Education and the Association of American Geographers. While they have been supplanted by the National Geography Standards, they provide an effective organization of the teaching of geography."

Five Themes of Geography are:

•Location
•Place
•Human-Environment Interaction
•Movement
•and Region

An Excellent Series of Before-and-After Photos from Japan

2011-03-14T21:21:00.003-04:00

From the New York Times is this interactive series of photos to show the after-affects of the tsunami.

Iceland - Land of Fire and Ice

2011-03-07T08:43:00.002-05:00

Just a short summary of Iceland's geology is linked above. If given a chance to visit a foreign country (already been to Mexico and Canada), Iceland would be my first choice (in the summertime), to have a "look-see" at this exposed part of the Mid-Atlantic Ridge. And to load up my digital cameras with photos.

Anthropogenic Earthquakes in Iceland

2011-03-07T08:17:00.002-05:00

Recently, there have been some swarms of earthquakes in Iceland, clustered around the southwestern part of the island nation. At first I thought this was "magma on the move", but the above-linked article suggests that the injection of cold water into geothermal sites may be causing the swarms (assuming we are talking about the same areas).

That humans can cause small earthquakes is nothing new. The removal of overburden at quarries, the backing up of water behind new dams, the injection of waste fluids into deep wells, and probably hydraulic fracking have all caused minor earthquakes.

If these swarms are not in the same geographical area as those illustrated last week in another source, I will update this post.

What a Geologist Sees - Part 35 - My Favorite Geophoto

2011-03-06T14:10:00.005-05:00

It is so hard to pick a favorite for Accretionary Wedge #32.

The Eagle Mts. (an Oligocene caldera) were the site of my originally-intended Master's Thesis work, during the summer of 1978. The photo here was taken from the East Mill area, where we camped, for several weeks, while we mapped the southeastern portion of the mountains. In the near foreground is a portion of Wyche Ridge, composed of Cretaceous sedimentary rocks, forming part of the margin of the caldera.

Eagle Flat is in the middleground and the Carrizo Mountains are in the background (and maybe the Beech Mountains and/or the Sierra Diablo in the far background, too). Alamo Springs may be visible from this location, also.

Aside from the El Paso area, within this view is probably the greatest geodiversity in Trans-Pecos Texas, though some might argue that point. In the background are several outcroppings of Proterozoic metamorphics and in the near foreground are the aforementioned Oligocene ash flow tuffs of the Eagle Mountains.

Within this view is the Texas Lineament, the northeastern edge of the "Chihuahua Tectonic Belt", and related features.

Aside from this, part of the exploits of the 9th and 10th U.S. Calvalry (the Buffalo Soldiers) against the Apache Chief Victorio took place within sight of this area.

To the right of the view, maybe 40 miles or so away - to the southeast - are the Davis Mountains. Within the mountains are the Ft. Davis historical site, one or more wineries, the Chihuahuan Desert Museum, and the McDonald Observatory.

To the left, maybe 80 miles or so away - to the north - is Capitan Peak and the Guadalupe Mountains, McKittrick Canyon and Carlsbad Caverns. So much to see.

I discussed some other favorites in this post.

What a Geologist Sees - Part 34 - Urban Beaches

2011-02-27T02:27:00.006-05:00

The photo above, from near the Portside Towers in Jersey City, NJ is not intended to represent the entirety of "urban beaches", but rather to consider what makes up a particular sand and where does all that stuff come from?

The darkness of the sand suggests a significant heavy mineral percentage, however it is likely that as the tide was receding, the last waves moved the lighter quartz downslope, exposing a thin veneer of heavy minerals. Under the microscope, heavy minerals are not the dominant mineral-type. As in most sands, quartz is the dominant mineral.

To get a wider perspective of the location, the large building in the left foreground is the Goldman Sachs building. In the right background is a portion of downtown Manhattan, with the Hudson River between the two. To the left of the beach is a narrow spit of land adjacent to a portion of an abandoned, historic canal.

In an effort to prevent erosion of the narrow spit, a wide variety of materials have been piled in the upper beach area, as well as miscellaneous old tires as well as other items of human flotsam and jetsam.

The remainder of the photos are to illustrate different perspectives on the beach materials that contribute to the sand chemistry with the never-ending wave action.

Under the microscope a brief examination of the sand - without concern to relative percentages - the constituents of the sampled beach sands include: 1) Angular quartz; 2) Well-rounded quartz; 3) Brick; 4) Glass; 5) Coal fragments; 6) Greenish Fe-Mg minerals; 7) Garnet; 8) Rutile; 9) Magnetite; 10) Ilmenite; 11) Slag,...

Among the particles, there are some odd, spherical grains that seem slightly magnetic, a quick guess might be magnetite, slag, or (least likely) Fe-Ni micro-meteorites. There will be some more examinations of the sand and the spheres in particular.

The Results of Accretionary Wedge #31 are Posted...

2011-02-27T02:22:00.002-05:00

Here and Here at The Geology P.A.G.E.

Here is my humble contribution.

Enjoy.

All Owls are Equal, But Some are More Equal Than Others

2011-02-24T08:58:00.005-05:00

You may well remember the controversy of the 1980s and 1990s over the apparently-declining numbers of Northern Spotted Owls in the Pacific Northwest. The Spotted Owl (Strix occidentalis) population of the Western United States is actually made up of three, closely-related subspecies, the Northern Spotted Owl (Strix occidentalis caurina), the California Spotted Owl (Strix occidentalis occidentalis) and the Mexican Spotted Owl (Strix occidentalis lucida).

This source provides some information about the range and habitats of the Spotted Owls, as well as the recently-recognized competition from its close relative, the larger Barred Owl (Strix varia).

From the Answers.com link (with slight paraphrasing):

...The nearly contiguous range of the Northern Spotted Owl extends from SW British Columbia south through western Washington and Oregon through the north-central coast of California.

The range of the California Spotted Owl overlaps the range of the Northern Spotted Owl in the southern Cascade Mountain Range, and extends south through the western Sierra Nevada to Tulare County, CA. Discrete populations of the California Spotted Owl also occur in mountainous areas of coastal and southern California from Monterey County to northern Baja California.

In the United States the Mexican Spotted Owl occurs in geographically separated populations in mountain ranges and canyons of Utah, Colorado, Arizona, New Mexico, and extreme western Texas. In Mexico it ranges from Sonora, Chihuahua, Nuevo León, and eastern Coahuila through the Sierra Madre Occidental and Sierra Madre Oriental as far south as Michoacán...

For the original citations and more information, please see the Answers.com entry.

Within the realm of nature, it is not unusual for there to be more than one reason for something happening. Habitat-loss due to logging and other events, e.g., the Mount St. Helens eruptions and windstorms, has been cited as a significant cause of population declines. More recently, the apparent entry of the larger Barred Owl into the ranges of the California and Northern Spotted Owls has resulted in population declines due to the Barred Owls being: 1) More aggressive in territorial defense; 2) Having a broader (more adaptable) diet and; 3) Occurring in more varied habitats. As the Barred Owls are closely-related (having had a common ancestor in the recent past), there is some hybridization in the overlapping areas, blurring the distinction between the Barred Owl and the Spotted Owl.

So, there appears to be a combination of human influences and natural influences in the changes facing the Spotted Owls. Unfortunately (from the title-linked article), some people in the Federal Government are of the opinion that these changes need to be "stopped" by intervening and killing at least some of the Barred Owls in the range of the Northern Spotted Owls. Rather than letting "nature take its course."

As both species occupy the same niche in their habitat overlaps - thus there are niche overlaps and habitat overlaps - under entirely-natural conditions, the Barred Owl would eventually dominate the Spotted Owls, forcing the Spotted Owls to: 1) Migrate to find other habitats with less competition; 2) Engage in Resource Partitioning (finding other food sources in the same habitat) or; 3) Become extinct. It is not "fair", but it is "nature's way."

These Secondary/Tertiary Carnivores serve to keep predated species population numbers under control and though part of this issue may be due to human intervention, humans "playing favorites" among the predators may lead to "unintended consequences". It might be better for the humans to resist their temptation to "make things more fair" and just sit back, watch, and learn from this event, as it unfolds.

Playing in the Snow

2011-02-24T08:02:00.006-05:00

While we were visiting our daughter and her family in Jersey City, NJ - for Christmas - we were gifted with the 6th heaviest snowfall in NYC history. The Jersey City-area received about 23 inches itself.

So after 2 - 3 days of playing with my grandson and faced with the beginnings of "cabin fever" (including issues with the wireless internet), I ventured out with my cameras.

The "dryness" of the snow and the almost-constant wind during and after the snowfall resulted in "sedimentary structures" and eolian, dune-like features (2nd photo) in the snow drifts.

The shifting wind directions and wind speeds interplayed with trees and artifical structures to produce a number of interesting scour and dune features analagous to what one might see at the leading edge of a dune field, prior to obstructions being totally covered by the advancing, fine-grained sand.

In all of the photos, except the second one, the wind erosion has revealed the (layered) stratification of the snow. As in the case of bedding planes in layered sediments and sedimentary rocks, the revealed layers suggest a brief cessation of deposition during the snowfall (perhaps due to increased wind gusts), when there was a slight consolidation (freezing) of the exposed snow surface, which was then followed by another round of snow deposition.

If this snow had fallen at a slightly-higher temperature and without the wind interaction, these "sedimentary structures" would not have been formed, nor preserved. Other deposition and erosion analogies could be applied in this setting, comparing the contrasting the effects of water and wind in shaping short-term and long-term landforms, both large and small.

An Interesting Geology-Related Book [Original Post Date 11/02/08]

2011-02-21T08:02:00.001-05:00

While browsing a used book store a little over 2 years ago, I picked up an interesting book, "Volcano Cowboys", by Dick Thompson.

It is about the quantum leaps made in understanding volcanoes, especially the explosive composite volcanoes, between the time of the Mount St. Helens eruption (1980) and the Mount Pinatubo eruption (1991). Having skimmed through it and then reading through most of the first chapter, I have already learned several new things, including learning about the Osceola Mudflow.

As composite volcanoes are the tallest of the volcanoes, it is not unusual for them to have glacier-capped peaks. When an eruption suddenly melts tons of ice and snow and it mixes with the previously-erupted ash and broken rock, it can be a recipe for disaster, producing what we call lahar flows (volcanic mudflows). A lahar killed an estimated 23,000 to 25,000 people in Armero, Colombia, in the middle 1980s. An "average" lahar may have a consistency of wet concrete and carry with it boulders the size of cars and downed trees.

Mapping by USGS geologists revealed that the Osceola Mudflow was produced by a partial collapse of a portion of Mt. Rainier, about 5700 years ago. It traveled a reported 60 miles from Mt. Rainier to Puget Sound. The worst part is that today, five towns have been built on the volcanic sediments of the Osceola Mudflow. If it happened once, it is likely to happen again.

There could well have been a few human inhabitants of the Puget Sound area at that time.

Just something to consider if you ever get a job offer from the Seattle/Tacoma area.

A Brief Explanation for Any Visitors...

2011-02-21T07:23:00.000-05:00

For those posts with [Original Post Date .......], that means the post was copied from another blog of mine, a more eclectic one that includes political rants and other stuff. This blog is just supposed to be about science. I may transfer (actually copy) a few more posts from the old blog, as time permits.

Natural Gas in North Carolina,...Perhaps [Original Post Date 05/21/09]

2011-02-21T07:22:00.001-05:00

According to this geology.com article, technologies now being practiced in areas producing shale gas might be utilized in two Triassic "Newark Basins" on the North Carolina Piedmont, the Dan River Basin and the Deep River Basin. (I tried to copy and post the NC map shown in the linked article, but it didn't work. I also tried to find a suitable diagram of a graben basin, with no luck.)

Basically, the Newark Basins are a series of elongate graben basins that form during periods of crustal extension. When the brittle crust is stretched and broken, some sections of the crust will subside along normal (gravity) faults. These basins are related to the Triassic and Jurassic Periods when Pangea was being stretched in "preparation" of splitting to begin the growth of the Atlantic Ocean basin. Before the basins were connected and deep-enough for ocean water ingress, they existed as inland basins with lakes and swamps. Without through-flowing river systems, organic material preserved in the shales and silts of these swamps could generate natural gas and oil under certain conditions (there is already some oil (and maybe gas) production from Newark Basins in other states).

Offshore Oil Rigs and Coral Reefs Co-existing [Original Post Date 06/03/08]

2011-02-21T06:33:00.003-05:00

Here is an article addressing some of the concerns about offshore drilling in the Gulf of Mexico.

Offshore oil platforms have operated for decades at the Flower Garden Reef. Here is more on this reef, off the Texas/Louisiana coast. The benefits of rigs to certain organisms are described here. Basically, rigs create new vertical habitats for organisms that must attach to some sort of structure. Once these attaching organisms are established, other organisms are attracted to the area. From the following link:

..."Natural structure and hard bottom are rare in the Gulf of Mexico where the bottom is pretty much a vast featureless plain of mud and sand. Where structure does occur, natural or otherwise, it is like an oasis in a desert. Virtual gardens of sessile (permanently attached) invertebrates like barnacles, corals, sponges, clams, anemones, bryozoans and hydroids quickly attach to every available surface and in every nook and cranny. "...

When the well (or wells) "plays out", removing the rig structure would damage the established reef organisms and disrupt the system. So a program was established to leave the structures in place (below a certain depth) and use the rig housing as additional structure for reef growth.

Rigs-to-Reefs program. From this website:

..."Since 1990, cooperating oil and gas companies have donated more than 64 obsolete petroleum platforms and contributed one half of the savings realized by reefing their rigs to the Artificial Reef Fund. These dedicated funds allow the Program to be relatively self-sufficient and finance research, administration, maintenance, liability coverage and construction of new artificial reefs."...

It is possible that the corals and other organisms in this area (SE of Galveston) are simply hardier, due to the natural oil seeps in the bottom of the Gulf. Whether or not reef organisms, in other areas, would "welcome" oil rigs might be debateable, but the record looks good. Imagine the disruptive scenario when a well plays out after decades and an emotion-driven demand is made for a total removal of the structure, even that portion well-below the wave base. Or imagine the damage done if the oil companies are not allowed a tax write-off for the abandoned rig.

These benefits are brought about by the free-market system and the sensible give-and-take regarding governments and their regulations. None of this is to suggest that these endeavors are risk-free (that world doesn't exist), but risks can be managed and minimized.

Our oil companies do listen to public concerns, but sometimes it takes years to find a solution to address the public concerns. Government-owned firms of China, Cuba, or Venezuela may not find Public Relations to be a priority.

Another Follow-Up, on the Subject of Gold...

2011-02-19T21:36:00.003-05:00

on a previous post (January 19, 2001) I copied a post from my other blog, on the presence of gold in a local stream. Just a small amount, judging by the tiny grains I have seen so far, but it is gold, nonetheless. The small, unnamed creek is a small tributary of the Chattahoochee River and the place I usually pan is about 1/4 mile from the river.

Now that I have had some time to think about it and revisit the place several times, there are two likely sources for the gold. It should be noted that this area is within a geologic feature called the Brevard Fault Zone (or Brevard Zone of Cataclasis), which has been (at various times) interpreted as a thrust fault, a normal fault, or as a large strike-slip fault. The rock types around here are mylonites, phylonites, muscovite button schists, sheared gneisses, quartzites, garnet muscovite schists, graphite schists,...things that wouldn't normally suggest the presence of gold.

The only thing I have seen along this particular creek (I need to explore more of the creek) that might be a likely source of gold is; 1) A siliceous, brecciated zone, with eroded, angular cavities in the rock suggesting past (sulfide?) mineralization; or 2) Eroded, old Chattahoochee River gravels and sands.

What remains is for me to "pan my way up" the creek to the point where the gold stops, i.e., I am upstream of the source. There are several branches of this creek, which cris-crosses several local roads, but there are enough wooded areas where I can collect sand samples, to take home for refinement panning. I use a screen atop a small bucket to sieve out the gravel and larger sand, leaving fine- to medium-grained sand within the bucket (which is obviously easier to carry).

I hope to get at least some of the searching over with before snake season begins.

Just a Quick Follow-up on the Previous Post...

2011-02-19T08:44:00.005-05:00

I referenced having found a grain of platinum while panning gold in north Georgia, 30+ years ago, in the "greater" Dahlonega area.

To explain a little further and to give some insight as to how I determined that the grain was most likely platinum, I did a few tests on it (it was l - 1.5 mm in diameter, large enough to study). From the way it "behaved" in the gold pan, I determined that it had a slightly-higher specific gravity than gold (check). It was maleable (check), it was light gray to whitish gray (check) and it was lightly magnetic - see below (check). Worked for me.

Though I don't remember where, I seem to remember that some element that commonly is in a natural alloy with platinum is magnetic. This Wikipedia entry is interesting, though it doesn't mention the magnetism property. Perhaps a tiny bit of nickel and/or cobalt? As one would expect platinum from mafic rocks, nickel would also likely be present in at least trace quantities.

Being a coin-collector at the time, I took the flattened grain and stapled it into a cellophane-center cardboard holder, which has been misplaced during one of the times that we moved. I am not convinced that it is gone forever. There are still a few boxes unopened from the last couple of times that we moved. Such as it is when we get older.

Accretionary Wedge #31 - Geo-Epiphanies

2011-02-18T19:00:00.007-05:00

This is not exactly a "new" epiphany, but one that has gradually become a greater interest. Sand. In particular, Heavy Mineral Sands. And the more diversity there is in the composition, the better.

I guess the epiphany is that - though I consider myself to be a field Geologist - it would be so easy to get "lost" in the endeavor of peering through a binocular microscope for hours on end. I actually did this with point-counting of petrographic thin sections, when I was an undergrad. In my youthful vigor, I decided it was necessary to count 500 points per thin section, for about 18 or so thin sections (for my undergrad "thesis"). That "cured" me of a desire for microscope work for a few years. My Master's Thesis was field mapping-oriented, so there were only 4 or 5 thin sections, with only a minimum of point-counting.

Anyway, the junior college at which I teach part-time is gradually building a sand collection. Students and faculty (and our friends) have been repeatedly asked to bring a ziplock bag of sand from a vacation spot. Some sand samples which have been collected (by my friends and relatives) include from Jamaica, Grand Cayman, and the Giza Pyramids.

Being a native of north Georgia, gold panning has long been a hobby of mine, but the heavy mineral concentrates in each pan have usually been discarded after any gold (or platinum in one case) has been picked out and saved. That includes heavy mineral concentrates from places I may never again have time to visit, such as the South Fork of the American River, near Coloma and Placerville, California or Aguirre Springs, Doña Ana County, New Mexico (above photo). Nowadays, I have a bit more respect for heavy minerals. Here is a brief blogpost (primarily for non-geologists, including my students). Though, as the intense study of heavy minerals is a bit esoteric, finding texts and articles (on how to distinguish monazite from zircon, for example) is a bit difficult.

After looking for new and interesting lab assignments for my lab classes, I began to spend more time looking through a binocular microscope at sands in general and heavy mineral sands in particular. Here is an example of an online sand exercise. As for studying local north Georgia heavy mineral sand samples, it becomes easier to keep the students' attention, if you tell them that there might be gold in their particular sample. I also tell them that small diamonds have been found in several Georgia heavy-mineral concentrates.

The above-linked online exercise led me to seek, not only creek and river sand samples, but beach sand samples, too. In contrast to the beach sands of the Georgia barrier islands - which are usually 99%+ quartz, the sands of the New York City-area are a fascinating mix. The "urban beach" photo above is from near the Portside Towers in Jersey City, NJ (near where my daughter and her family live). Between the chunks of old bricks, concrete, coal fragments, and other materials dumped for erosion control, you can see the distinctive dark color to the sand that hints at an interesting mix of heavy minerals.

Though I haven't studied these sands in detail, the literature suggests they are largely magnetite and garnet. One of my goals is to visit Montauk Point on Long Island and Sandy Hook, NJ to collect some sand samples from those two areas. And I would also like to revisit the area near Auraria, Georgia where I found a grain of platinum (along with the gold) in my pan, so many years ago.

Yeah, with a good supply of heavy-mineral samples, I could stand to be "chained" to a microscope for a little while. So, "Here's sand in your eye."

Milankovitch Cycles and Carbonate Deposition...

2011-02-13T10:14:00.005-05:00

Are described in this post over at Rapid Uplift, with important links to other posts, including - at Open Mind - Glacial Cycles, Part 1 and Glacial Cycles, Part 2.

Just a brief bit from Rapid Uplift:

"...Milankovitch cycles are orbital cycles which result in periodic fluctuations in the amount of solar energy received by the earth. Three types of cyclical changes in the earth's movement around the sun, eccentricity, obliquity and precession are said to determine climatic cycles on earth."...

A bit more:

"...One explanation has been that Milankovitch cycles causes growth and decay of ice sheets. This periodic locking in and release of sea water by ice sheets causes fluctuations in sea level resulting in changing water depths and cyclical deposition of sediment. A great many carbonate sequences have been explained as being deposited under the influence of sea level changes caused by such orbital forcing. The image below is one of the most famous examples of Milankovitch forced cycles.. the Triassic dolomite platform which makes up the famous dolomite mountains in Italy."

Stated in a different way, whenever you seen the alternations of sedimentary layers, in relatively thin layers, it is telling you that there were fluctuations of some sort. Milankovitch cycles (as described in the linked posts above); tectonic fluctuations of sea level and/or the local sea bottom; or fluctuations in sediment supply, which may reflect climate and/or tectonic fluctuations in the sediment source-area (on a nearby land mass).

Thicker layers represent more long-term fluctuations of the same types, as long as the alternating layers each remain within a given range of lithologies.

New Madrid Earthquake Bicentennial Begins

2011-02-13T09:48:00.002-05:00

Here linked are several YouTube videos related to the 1811 - 1812 earthquakes in the New Madrid Fault Zone. As this area of the Mid-Continent was not settled during that time, the cities that have grown since then are not used to earthquakes, as are California cities. In other words, they are so not ready for any significant earthquakes.

This first video is from Mitch Withers:

The second video is from Walter Mooney:

I plan to add more...

Geo-Epiphanies?

2011-02-10T06:46:00.004-05:00

Accretionary Wedge #31 is now open and accepting entries with a February 18 deadline.

The subject is "What geological concept or idea did you hear about that you had no notion of before (and likely surprised you in some way)?".

The hosting Geoblog for this round is The Geology P.A.G.E. (Presenting Alternatives in Geoscience Education).

What a Geologist Sees - Part 33 Heavy Minerals [Original Post Date 10/29/10]

2011-01-26T20:56:00.003-05:00

Heavy minerals have several definitions;
1) Specific Gravity (density) greater than quartz (>2.65 times the density of water).
2) A relative resistance to chemical weathering, greater than that of most silicate “rock-forming” minerals (except quartz).
3) In their original host rocks, they usually constitute trace quantities.

Some “common” heavy minerals and their respective Specific Gravities (vs. Quartz 2.65) include:

Zircon 4.6 – 4.8
Monazite 4.6 – 5.4
Tourmaline 3.0 - 3.3
Rutile 4.2 – 4.3
Ilmenite 4.5 – 4.7
Magnetite 4.9 – 5.2
Staurolite 3.7 – 3.8
Kyanite 3.5 – 3.7
Garnet 3.56 – 4.32
Diamond 3.5
Gold 15.6 – 19.3
Platinum 14 - 19

The process of releasing heavy minerals begins with the chemical and physical weathering of a given rock unit. In this Lithonia Gneiss saprolite, there is quartz, clays, altered minerals, and heavy minerals.

When the broken-down rock materials (clasts) are moved down-gradient - usually by water (erosion) and gravity - they are separated by density during high-energy water movement (floods).

The dark metallic colors of ilmenite, rutile, and magnetite help make placer concentrations of heavy minerals more easily seen.

Variances in water velocity help concentrate heavy minerals into "placer" deposits. Close to the source areas for mafic rocks, heavy minerals can include olivine, pyroxenes, and amphiboles, but these are unstable and will undergo degradation to clays during transport.

In the settings of a small to medium-sized creek, areas where the water velocity slows, such as the inside of a meander or on the upstream side of a boulder or other obstruction allow for the deposition of heavy minerals. If one is interested in panning for gold, the scoured area at the foot of a small waterfall might be a favorable site, also.

Another place where heavy minerals accumulate is in beach sands. In the southeastern portion of the United States, the white quartz sand beaches do contain small amounts of locally-concentrated heavy minerals in discrete stringers. In areas where there is little separation between the crystalline rocks and the shoreline (as in the northeastern United States), the heavy minerals present are much closer to their original source area.

The dark areas of this Jersey City, NJ urban beach are enriched with heavy minerals derived from the weathering of igneous rocks in the area and the erosion of glacial sediments. This heavy mineral portion of sands include a healthy quantity of garnet fragments. Other beach deposits in the NYC area - especially Montauk Point, Long Island - are even more garnet-enriched.

What a Geologist Sees - Part 32 [Original Post Date 5/27/10]

2011-01-26T20:50:00.004-05:00

[Subtitled: Geophotos, Memories, and Hopes]

Within my geophoto database, the photos that are among my favorites include those from the Eagle Mts. (West Texas), the Bisti Badlands (San Juan Co., NM), and Monument Valley (UT/AZ). [The labeled photos have been used in some of my classroom Power Point presentations.]

Yeah, I got a bit carried away going down memory lane.

The Eagle Mts. (an Oligocene caldera) were the site of my originally-intended Master's Thesis work, during the summer of 1978. The 1st photo here was taken from the East Mill area, where we camped while we mapped the southeastern portion of the mountains. In the near foreground is a portion of Wyche Ridge, composed of Cretaceous sedimentary rocks, forming part of the margin of the caldera.

Eagle Flat is in the middleground and the Carrizo Mountains are in the background (and maybe the Beech Mountains and/or the Sierra Diablo in the far background, too). Alamo Springs may be visible from this location, also.

This was one of the few close-up photos of the pyroclastic textures that I took that summer. I guess I planned to get more in future trips, but I got "distracted" by events in my personal life and never finished this project. (I did start another thesis project in 1985 in the Aden Volcanic Field). I would, love the opportunity to take my son 4-wheeling back in the Eagle Mts., - maybe someday. To enjoy the quiet and get a few more photos and maybe find that rock hammer that I lost.

The Bisti Badlands in San Juan County, NM were the site of a 1979 summer job. I was hired to assist in a "fossil recovery project", locating Cretaceous vertebrate, invertebrate, and permineralized wood samples, prior to the opening of a coal mine. During the early part of my six weeks there, I took hundreds of slides, then unbeknownst to me, the shutter on my Miranda camera jammed.

It rained almost every day the first two weeks we were there and the clays in the Fruitland Fm. are like grease when they get wet. After that first two weeks, I don't recall anymore rain for the remaining four weeks of the project.

The primary goal of our project was to mark the location of every dinosaur bone in two and a half square miles, recover all loose bone fragments, then leave the removal of large pieces to the University of New Mexico. (Sometimes when I talk about being a Geologist to a bunch of kids, I tell them about the summer I got paid to look for dinosaur bones, that usually catches their attention.)

We were supposed to continue this same project in the summer of 1980, but the permits between the state and federal land didn't get resolved in time. I would have enjoyed another go-round in this area.

It has been years since I read any reports generated by this project, but I seem to remember my lead professor telling us that most of the bones we found were of hadrosaurs (duck-billed dinos). We also found turtle shells fragments, crocodile scutes, and a few fresh-water bivalves (the ecosystem had been an Everglades sort of setting).

It was always fun to find one of these areas just littered with permineralized logs, though they were not generally as colorful as the wood from the Petrified Forest.

I hope this stump was retrieved for a museum or at least given a place of honor outside of a college classroom building.

The site where I collected this "clinker zone" shale (actually outside of our study area), with the plant fossils is one of those places that I regret not having collected more samples from. I only picked up two pieces and gave one away during the intervening years. I wish I had filled a bucket.

Monument Valley is a place I have not yet visited, but someday hope to. My geophotos from Monument Valley are scanned slides taken in the summer of 1980 - by my Dad - when he and my Mom were on their last vacation together. He passed away in November, 1980.

I use these photos, along with my photos of Canyonlands NP and the Grand Canyon when discussing Colorado Plateau stratigraphy...

...and when discussing arid-climate weathering and erosion characteristics...

...and when discussing things like eroded volcanic necks.

Other stops on that trip included the Painted Desert/Petrified Forest,...

...and Dinosaur National Monument,...

...Yellowstone,...

...and the SD Badlands.

My Dad was not a geologist, but he did enjoy learning about new things. I will forever be thankful that he got me interested in photography.

What a Geologist Sees - Part 31 [Original Post Date 5/16/10]

2011-01-26T20:44:00.002-05:00

OK, maybe it was because I was raised with both cats and dogs. Or there may be other reasons for my eccentricities. That can be discussed at another time and place.

As for Geology, I am one of those strange creatures that dwells within both "Soft-Rock Geology" and "Hard-Rock Geology". And for that reason, I am regarded with some suspicion by the zealots in either of these two camps.

For the normal folks out there, "Soft-Rock Geology" this is not an analysis of the type of music that we like, but rather an informal division of Geology that includes the study of sedimentary rocks, fossils, stratigraphy, geomorphology, weathering and erosion, Earth history as revealed in the sedimentary rocks, petroleum-related issues, and so on.

"Hard-Rock Geology" is the study of igneous and metamorphic rocks, minerals, mineral economics, structural geology, plate tectonics, mass wasting, and so on.

I enjoy all aspects of Geology, thus I have always seen Geology as a buffet, of sorts. This is reflected in my coursework and various jobs. As I enjoy a wide range of Geology, I have had no desire to become an expert at anything, rather a learned student about different geo-disciplines. As an opportunity presents itself, I pick from the Geological Buffet. It might be fossils this time, metamorphic rocks next time, tracing old river terraces another.

It has been my experience that, the more interests one has, the less likely one is to become bored with a situation. This also extends beyond Geology to the hobbies (and other science interests) that we have, in my case, Photography, especially Scientific Photography. Having a wide range of interests, I generally am able to find something to do, if the weather is good while visiting an area. I am not as likely to go "stir crazy" as an igneous or metamorphic petrologist would, if confined to Mississippi or Florida or Kansas.

In other words, I have less difficulty in finding a way to entertain myself, geologically speaking. I used to find river gravels boring, until I started noticing them on hilltops and began to think about "how this came to be". If I happen to see old gravels a half-mile (or more) from a present-day river, that immediately piques my interest.

I used to consider sands to be a tedious subject, until I started looking at them under a microscope, to look beyond the dominant quartz in most samples, to the accessory and trace minerals and what they mean.

If I happen to be in a place where I have already "scoped out" the local geology, I can go back for a more detailed look, just to find something "new". It always helps to have done a little study beforehand, online or by way of various geological publications, whether they be from governmental entities or private organizations.

I just wish I could convey the notion to my teenaged son that - you are only bored if you allow yourself to be. I wish I could engender that fascination with learning that I have come to value. That is one of the most valuable tools I have picked up along the way in my geo-journey. There is almost always something new to see, even when I revisit the same patch of woods for the 10th time.

So, herein this rambling prattle has been my attempt to explain my wide-ranging interests in Geology. An attempt to explain the "Method to my madness".

The Okie Dokie Diamond [Original Post Date 3/13/06]

2011-01-19T21:00:00.002-05:00

Many people may not be aware of it, but Murfreesboro, Arkansas is the only place in the entire world where common people can pay a small fee and search for diamonds and keep everything that they find. All other diamond producing areas are owned/controlled by large corporations or governments.

From MSNBC News, an Oklahoma State Trooper, visiting the Crater of Diamonds State Park with his family for the first time, found a 4.21 carat, canary yellow diamond that is said to be flawless. Talk about beginner's luck!

The park is approximately 37 acres of ground that is periodically plowed. Visitors are allowed to crawl about on their hands and knees, that is how I found my small white diamond (.37 carats) on my first visit in 1973. There are other areas where people can dig and sieve sand and gravel in water to look for diamonds.

When I was there in the spring of 1978, a couple from Dallas was looking in the same area as I was looking. I left in the mid-afternoon to do some other things in the area. At dusk, I was parked along the road into town, looking for old beer cans in the woods when the Dallas couple recognized my truck and pulled over. They asked me to take a look at what they found and to tell them if it was a diamond. It was a 4 carat, brown diamond, not of gem quality, but with the classic octahedral diamond shape. I got to hold it and I was the first one to confirm that it was a diamond (the park office had closed for the day). I later saw a short newspaper article in a Dallas paper, wherein that diamond was valued at $4,000 because of its size, classic crystal shape, and it being an American diamond. And that was 1978.

The article mentioned that 84 diamonds have been found so far this year. When I was first there in 1973, they said about 250 diamonds per year were found by visitors. Most of them are not gem quality, but once in a while, someone finds a "blockbuster" of a diamond, worthy of faceting and mounting in jewelry. The three main colors at the Crater of Diamonds State Park are white (60%), brown (21%), and yellow (17%) - according to the linked site below. 383 diamonds were found in 2004 and 536 in 2005. The higher numbers than the 1970s may be partially a function of higher numbers of visitors and perhaps more serious methods of searching, perhaps more digging and less crawling.

As mentioned above, it is an Arkansas State Park, open to the public. The state of Arkansas has toyed with the idea of selling the property to mining company, but public pressure has so far preserved the status quo. I know that Libertarian/Conservative purists disapprove of government ownership of land, but this place is so unique, I think it should stay as a state park.

The first diamonds were found 100 years ago, when the area was a farm. The farmer, when dressing out chickens to eat, found shiny stones in their craws (not having teeth, some birds swallow small stones to aid in the digestion process and the shiny nature of the diamonds caught the eye of the chickens). The stones were identified as diamonds, but there were never enough to support a mining operation, so it became a tourist attraction. In 1972, it became a state park.

If you click on the Park link above, the middle-aged black man in the center "works" at the park. Every day the park is open, he is there to pay his fee and that is what he does all day, dig for diamonds. He was there the last time I visited the park in 1983 or 1984 and I talked to him briefly. He doesn't find a diamond every day, but he finds enough to scratch out a living. Some of his diamonds may be among the Arkansas diamonds for sale on this website.

If you ever go there, don't expect to find a diamond, but there is always a chance. There are other minerals of interest to kids, quartz crystals, amethyst, calcite, peridot, agate, conglomerate (a type of sandstone composed of rounded river pebbles) and other minerals. Just keep everything that might even look like a diamond, and the rangers at the park are more than glad to look over what you have found and tell you "what's what".

Only in America!

Gold! I Found Gold! [Original Post Date 2/20/06]

2011-01-19T20:51:00.000-05:00

Naw, I ain't talking about the Olympics.

I found a little bit of gold in a small creek, on the west side of my hometown. It ain't enough to worry about, but I just had to tell someone!

To be honest about it, a local man told my dad 25+ years ago that he had found gold in this particular creek, but my dad was skeptical and he didn't get a chance to check it out before he passed away in late 1980. After I moved back here in early 1991, from time to time I thought about the creek, which is behind an office park. Finally, last summer I decided to check it out.

I "ran" a (gold) pan of sand from the creek and found a couple of tiny, tiny grains of gold. I went back last week and ran another pan and found three tiny, tiny grains. In fact, you need a hand lens to identify it as gold, but gold it is.

There are other interesting minerals in the "black sand" that concentrates in the bottom of the gold pan. These minerals, more dense than quartz, are referred to by geologists as "heavy minerals" and are usually composed of metallic oxides and other unusual minerals and it this case it includes small garnet crystals and fragments of larger garnets and other colorful stuff.

Yeah, I am having a mid-life crisis and this gives me an excuse to play in a creek. Heh.

For Any Visitors...

2011-01-19T20:42:00.002-05:00

The reasoning behind the reposting of old science material is that I am copying it from my original blog, to separate it from the political stuff that some folks don't like.

Interspersed will be new material, when time permits.

A Slip and a Fall [Original Post Date 1/23/06]

2011-01-19T20:40:00.001-05:00

In the news is a story from Utah about a small hiking party, wherein one member slipped and knocked two other hikers about 60 feet down the mountainside, resulting in significant injuries to the two. They and the others have been rescued, so hopefully all will be well after the healing process.

It just reminded me of one of the few times I have really fallen while doing geologic work and how that fall might have changed geologic history (not my contributions, but someone much more important).

During the late 1970s or perhaps early 1980s, there was a geologic convention in El Paso, where academic papers were presented and field trips took place. One of the attendees was Dr. Preston Cloud (1912 - 1991), the 1977 recipient of the Charles Doolittle Walcott Award, from the National Academy of Sciences. [Dr. Walcott discovered the Burgess Shale fauna in 1909.] Dr. Cloud's NAS citation was for:

"In recognition of eminence and distinguished achievement in the advancement of sciences in pre-Cambrian paleontology and the early history of life on the primitive earth."

Here is one of Dr. Cloud's photographs along with an explanation of some of the material that he studied. Here from Amazon.com is a listing of references to Dr. Cloud in other science books. "The Garden of Ediacara" (in which there were nine references) is about the Precambrian Ediacaran fauna of Australia, the most important, discovered fauna from the time before the Cambrian Explosion. Here are a few more web links about Dr. Cloud.

One of the convention field trips was into the southern end of the Franklin Mountains to observe large, fossil algal structures (I know, only geologists dig this stuff) that had been studied by one of the UT El Paso geology professors. Dr. Cloud was one of the guests of honor on the field trip and I was tagging along with the rest of the geology grad students.

After observing the algal structures, we returned down the mountainside to the vehicles to go elsewhere on the field trip. On the way back down, Dr. Cloud paused at the top of a small cliff (perhaps only 10 - 15 feet high), to observe the scenic view of the Hueco Bolson and the Rio Grande River Valley southeast of El Paso. I was a few yards upslope and behind Dr. Cloud and when I saw him stop to take in the view, I attempted to stop my downslope steps. But instead, I stepped on some loose pebbles and started tumbling. I ended up on my hands and knees scant inches (4 to 6 inches) behind Dr. Cloud, scant inches from knocking a world-famous geologist off of a small cliff in the Franklin Mountains.

Maybe I am slightly over-dramatizing this event, but to this day I thank God that my legacy as a geologist wasn't written that day. True, the vertical distance wasn't that much, but below there were boulders and numerous cacti on the mountain slope. I am not even sure if Dr. Cloud knew how close I came to knocking him over the edge. I am not even sure that the lead professor knew and I never told him until I emailed the story to be part of his retirement party 3 or 4 years ago. He didn't reply, though I can imagine him slapping his forehead and saying "OMG" at the thought of what almost happened.

It was such an "OMG moment", I don't even remember the rest of the field trip. I don't even remember if I was driving one of the vehicles later or not.

Maybe a guardian angel stopped my tumbling or maybe it was shear dumb luck.

What a Geologist Does [Original Post Date 3/29/10]

2011-01-17T23:51:00.001-05:00

Aside from my part-time Geology job and my part-time teaching...

What I am doing right now includes (when time permits, largely on weekends):

1) Retyping/rewriting my Master's Thesis (from 1989) and scanning the photos and related 35 mm slides. (It was probably one of the last theses typed on an electric typewriter). Because of the binding, scanning all of the text would be a hassle.

The reason I am doing this is to be able to send some info to a vulcanologist with the Hawaii Volcano Observatory. A while back, he contacted me with information relating Hawaiian volcanic shatter rings with the Quaternary "explosion-collapse" craters that I studied in the Aden Basalts, in southern New Mexico. In other words, he thinks that the five craters I described are probably "shatter rings".

My thesis advisor and I had scoured the literature available in the middle and late 1980s and found no references pertaining to these craters, characterized by an encircling rampart of boulders and a collapsed central floor. If I can secure his permission to reference his work, I may work up an abstract for a GSA meeting next year, if it doesn't conflict with a more substantial publication he has in the works.

2) Continuing the work on my science-photo CD. For the last 8 years I have been compiling a database of photos to use in my Geology and Environmental Science lectures. At this time, I am trying to fill in some missing categories. There are currently 900+ photos applicable to Geology, Biology, Weather (clouds), and Environmental Science.

I am greatly looking forward to going back to NJ and NYC this summer to get some photos of the glacial features of Central Park and maybe some of the terminal moraines on Long Island. Maybe I will get some good photos of the Palisades of the Hudson and some of the coastal features of New Jersey, including Sandy Hook. I would also like to collect some samples of the garnet beach placers on Long Island, i.e., heavy mineral sands dominated by garnet fragments.

3) Continuing work on a compilation of Cretaceous & Tertiary well logs from Burke County, GA. This began 10+ years ago while a co-worker and I were working on a state geologic survey project in the vicinity of the Savannah River. My friend is a well-known Gulf Coastal Plain stratigrapher and his detailed well-log descriptions were too voluminous to put in the original reports and our goal was to produce a separate report, which would hopefully resolve some of the stratigraphic nomenclature and correlation issues between this part of Georgia and adjacent South Carolina. [If memory serves me correctly, my friend logged about 13,000 feet of core for the Tritium Project.]

With my friend's retirement to Albuquerque a few years ago, it has hindered work on this paper (he was actually here a couple of weeks ago, looking at other Coastal Plain cores and rewriting well logs - once a stratigrapher, always a stratigrapher). If we ever get this paper finished, even if it doesn't get published, if we can print a few copies onto CDs and send them to some local colleges that might be interested, at least someone would have access to the descriptions to the cores for future projects.

4) Learning the "Ins and Outs" of Google Earth in tying GE images to visited sites and sample locations. As for the sample locations, my junior college is building a sand sample collection, i.e., various beach, river, and dune sand samples and I would like to be able to tie location maps (and descriptions of source area geology) to the individual sand samples.

5) Revisiting the trace fossils I found in the Permian Cloud Chief Formation in Southern Ellis County, OK. Originally found in July, 2007 and ID'ed as "Arthropod locomotion marks" by the Oklahoma Geological Survey, I recently did an internet search and determined that these are very likely Arthropleurid trackways. Only one side of each set was preserved, perhaps because the centipede-like creature was wider than the individual rock slabs. Though I hope to revisit the area again to do some more collecting and documentation, I doubt that it will be this summer.

What a Geologist Sees - Part 30 [Original Post Date 4/16/10]

2011-01-17T23:47:00.002-05:00

These thin sandstone slabs are from the Permian Cloud Chief Formation from NW Oklahoma. They were collected from downstream of Lake Vincent in southern Ellis County.

The bulk of the formation is composed of siltstone and claystone redbeds.

(Click to enlarge images)

Pictured are the tops of the individual beds. The 1 cm bars are accurate, to show scale.

A few months after dropping some specimens off with the Oklahoma Geological Survey, they told me that there were probably "arthropod locomotion marks". Being busy with life in general, I accepted the answer without trying to determine "what sort of arthropods".

Recently, while looking at some of the slabs, I revisited a point of previous curiosity. Each trackway seemed to not have a companion for the opposite side of the critter. Perhaps because the critter was wider than the slab of rock.

So I started doing an internet search of Permian arthropods. An early result gave the word "Arthropleurid" as a likely suspect. An Arthropleurid was a large, centipede-like critter, in some cases up to 6 feet long. A later result gave this article, concerning the Late Pennsylvanian Cutler Group, in northcentral New Mexico.

If I get a chance to revisit the area, I will be looking for wider slabs, to hopefully find more-complete trackways and to document the occurrence a little better. Would like to maybe do a short paper/talk, maybe for a future GSA regional meeting. Or if I don't, maybe I will have somehow inspired someone else (in Oklahoma) to do so.

[The comments were generated with the original 2007 post.]

What a Geologist Sees - Part 29 [Original Post Date 10/02/09]

2011-01-17T23:43:00.001-05:00

Shatter Ring on PKK Lava Tube (March 20-22, 2006) from this USGS site:

This video, shot by Tim Orr of the USGS, is of interest as I studied these Shatter Rings in the Aden Basalts of southern New Mexico. Not aware of the existence of other examples (20 years ago), we called them "Explosion-collapse" craters and I described 5 of them in my Master's Thesis.

Using the description from the USGS website, here is a description of the Shatter Rings:

"Shatter rings are circular to elliptical volcanic features, typically tens of meters (yards) in diameter, which form over active lava tubes. They are typified by an upraised rim of blocky rubble and a central depression."..."They form when lava pressure in the tube repeatedly exceeds the strength of the overlying rock. Repeated flexing of the lava-tube roof piles up rubble around the edges of the mobile area."

In the case of the shatter rings I studied, lava was extruded up through the shattered rocks and filled-in the bottom of the crater, creating a lava lake, which later collapsed after the lava below withdrew.

When I scan some more of my old slides and prints from my field area, I will write more about these features.

What a Geologist Sees - Part 28 [Original Post Date 9/13/09]

2011-01-17T23:37:00.001-05:00

Shales. Mudstone. Claystone. Clay. They are the most common sedimentary rocks or sediments.

Yeah, sometimes they can be a bit boring if we only look at them from one dimension. While on vacation, I searched this Tulsa, OK outcrop for more than a half-hour and found nary a fossil. As I was pressed for time and saw no other outcrops nearby, I kept looking.

In other shale outcrops, splitting apart the layers can bring nothing or it can bring to light a fossil leaf, a fossil seed, a fossil shell, a trace fossil,...

In the case of the specimen at left, this is a sample of shale that has been baked by an underground "coal seam fire" sometime in the past. The heat baked the shale to a natural ceramic and preserved the Cretaceous-aged fossil leaves within. (I regret not having collected more samples from this site 30 years ago.)

Shale is a clastic sedimentary rock that consists of compressed clay. It differs from claystone or mudstone by being "fissile" as shown in the upper photo. Fissile refers to the property of splitting into thin layers, which is caused by the alignment of the microscopic, flat, hexagonal clay plates (visible only to scanning electron microscopes). In the fissile shales, bedding planes are often observed, presenting the planes of weakness that allow the splitting.

Claystone or mudstone, while being hard, do not have the same alignment of clay plates, thus they fracture in a more "massive" fashion with no visible bedding planes, often leaving a curving "concoidinal" fracture, as seen below in the kaolin sample.

When younger or less-compacted (and therefor softer), as on the Gulf or Atlantic Coastal Plains, we refer to it as "clay".

As defined by the Wikipedia entry, "Clay minerals are hydrous aluminium phyllosilicates, sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths and other cations."

There are five groups (and other subgroups) of clay minerals, including some 14 minerals (one of which is not always considered a clay) - according to the Wikipedia entry.

Clays are derived from the chemical weathering of silicate minerals and rocks. Minerals such as micas, amphiboles, pyroxenes, but especially feldspars. In continental settings, such as exposures of highly-weathered rock, reddish colors (for the famous Georgia red clay) for some clays can come from iron-staining.

Once clays have been delivered to the river systems (including swamps and lakes) and then to the ocean, their eventual colors are a function of their environment of deposition. Due to the minute nature of the clay plates (less than .004 mm) and their buoyancy, quiet water conditions are needed for the clay flakes to finally sink to the bottom of the ocean (or other water body). Sometimes slight increases in water energy can result in silt (.004 mm to .063 mm) being deposited within the clay or as separated, interbedded layers. Silt is usually made up of minute silica (quartz) grains, but may include other minerals.

In the case of the Tulsa shale outcrop, this was probably an open-marine setting, where there was relatively good water circulation (and oxygen availability for bacterial degradation of any organics), usually yielding a light- to medium-gray color. The same is true for the shales interbedded with the thin limestones of this particular facies of the Ordovician Lexington Limestone. The alternating layers suggests fluctuations in the environment, due to changes in sediment supply, water depth, or other factors.

When you see reddish-colored shales or claystones (in a sedimentary setting), those were usually deposited in a continental or transitional setting, such as a river system, delta, or a tidal flat setting. The red color is due to the subaerial oxidation of the iron within the clay sediments. Usually the preservation of ripple marks suggests a certain amount of silt in the rock.

Currently, the most popular color of shale (for geologists) is dark gray to black. The dark colors are most-often due to the preservation of organics in stagnant (anoxic) conditions, where slow water circulation fails to replenish oxygen. So when organics drop to the bottom, the bacteria that would normally be there to "eat" them, are absent. This is the case in swamps (blackwater) or in restricted marine basins, e.g., the Black Sea or the deep part of the Gulf of Mexico.

This preserved organic material becomes the interpreted source of oil and/or natural gas, depending on the type of organics and/or the temperature conditions. An increasing amount of our domestic natural gas is being produced from Paleozoic and Mesozoic dark shales, such as the Marcellus, Barnett, Woodford, Eagle Ford, and other shales, due to our ability to "frac" (fracture) the shales using hydraulic pressure to shatter the shale and proppants (sand or minute ceramic spheres) to prop open those fractures. Without this process (or natural fractures), the shale is generally too "tight" to produce much of anything. Generally, the shales with a little bit of silt-sized silica are a little more brittle and frac more easily.

Another aspect of clay is that when compressed, the alignment of the flat clay plates makes the semi-impervious (or impermeable), i.e., they don't pass water or other fluids very well. This is why we use clays in ceramics. Layers of clay or shale can serve as "confining beds" to separate layered aquifers or as "caprock" to trap hydrocarbons.

There are other characteristics of clays that make them both a bane and a boon to humans. Some clays swell when wet and this can be useful when adding clay pellets to seal the annular space in a water (or other) well, but can play havoc with heaving (and cracking) of roads and foundations with wet/dry weather cycles. The brick steps to my back porch are a testament to this characteristic of rising and falling with wetting and drying, as they have broken loose from the foundation of the porch.

Clays also can act as absorbents for pollutants, whether in your cat's litterbox or in dealing with oil or other spills. They can be used in filtration settings, as filler material, as the "binder" for Kaopectate,...

To go any further would require re-writing "War and Peace" in a geological sense. I hope you get the picture that clay is more than just hardened mud.

For other "What a Geologist Sees" posts, click on the Tag below.

What a Geologist Sees - Part 27B [Original Post Date 5/04/09]

2011-01-17T23:29:00.003-05:00

...or would like to see.

Somewhat related to the last numbered What a Geologist Sees post (#27), here are the Top 15 places I would like to visit or revisit, now that I have a digital camera - after #1 in no particular order. [I may expand this to 20, later.]

1) Arches National Monument - I have been there twice (1977 and 1979) and both times my 35mm film camera crapped out.

2) Monument Valley, AZ and UT

3) Antelope Canyon, AZ

4) Valles Caldera, near Los Alamos, NM and some of the nearby Rio Grande Rift features, including some south of Albuquerque.

5) The basalt flows along I-40 near Grants, NM

6) Mount Saint Helens

7) Hawaii - primarily the big island

8) Zion National Park

9) Portions of Wisconsin, where there are glacier-related landforms. When I was there in 1982, I inadvertently opened the back of my 35 mm without reeling the exposed film back into the cartridge. D'oh! My brewery photos were safe on another roll, but I lost all of my geology slides.

10) Glacier National Park

11) Aden Basalt Field, southern New Mexico - I learned to hate it when I was working on my Master's Thesis 20+ years ago, but I actually miss those monotonous flows. There are many things to enjoy and photograph while doing a walkabout.

12) Yellowstone National Park - last time I visited was 35 years ago.

13) Devil's Tower, NE Wyoming

14) Exposures of the Niobrara Chalk in Kansas, Castle Rock and Monument Rocks. Better still, somewhere where collecting fossils from the chalk is legal.

15) Yosemite National Park - again, last visit 35 years ago.

16) I would like to replicate my 1974 trip across the western U.S. with a non-geologist friend. This time, I would insist on stopping to take some more photos. As I was still an undergrad at that time, I would have a much better idea of what I waas looking at this time. (I will update more later.)

What a Geologist Sees - Part 27 [Original Post Date 2/27/09]

2011-01-17T23:12:00.002-05:00

100 Things a Geologist Should See or Do

For the source of this list, see this link at Geotripper.

To see the entire list, visit the link. Printing the entire list is too long, so I will list the things I have done or seen and the things that I consider in the realm of possibility of doing sometime in the future.

Been there/done that:

3. See an active geyser... such as those in Yellowstone
6. Explore a limestone cave. Carlsbad Caverns in New Mexico, Luray Caverns, VA, Raccoon Mt., TN; Cumberland Caverns, TN; Mammoth Cave, KY
7. Tour an open pit mine,... a copper mine in Santa Rita, NM and a uranium mine in Sierra Peña Blanca, Chihuahua.
8. Explore a subsurface mine - a coal mine in Mexico.
13. An exfoliation dome, such as those in the Sierra Nevada - or Stone Mt., GA.
16. A gingko tree, which is the lone survivor of an ancient group of softwoods that covered much of the Northern Hemisphere in the Mesozoic. - Got one in my side yard.
17. Living and fossilized stromatolites (Glacier National Park is a great place to see fossil stromatolites - or the Franklin Mts., El Paso area while Shark Bay in Australia is the place to see living ones) - done 1/2 of that
19. A caldera - Valles Caldera, Los Alamos, NM, several calderas in West Texas
26. A large sinkhole - Silver Springs, FL
33. Petrified trees Bisti Badlands, San Juan County, NM (see this post)
34. Lava tubes Aden Crater, NM
35. The Grand Canyon. All the way down. And back. 1/2 of this, I have been on the South Rim of the Grand Canyon 4 times.
36. Meteor Crater, Arizona, also known as the Barringer Crater, to see an impact crater on a scale that is comprehensible - 1978
58. The Carolina Bays, along the Georgia coastal plains
62. Yosemite Valley - 1974
63. Landscape Arch (or Delicate Arch) in Utah - camera crapped out on both visits 1977 & 1979
80. The Black Canyon of the Gunnison in Colorado - 1977, 1979
84. Find a trilobite (or a dinosaur bone or any other fossil) - found plenty of fossils, including dino bones, but haven't found a complete trilobite, yet.
85. Find gold, however small the flake - numerous times in GA and CA
88. Experience a sandstorm - First spring in El Paso, 1977 and other times
90. Witness a total solar eclipse
95. View a great naked-eye comet, an opportunity which occurs only a few times per century
96. See a lunar eclipse

So, it looks like I have only done 21 of these things (or been 21 of these places). That is not to say I haven't seen a countless number of interesting things, but they might not be interesting enough to put on a Top-100 list.

Might go there/do that someday:

1. See an erupting volcano - I would like to visit either Iceland or Hawaii
2. See a glacier
4. Visit the Cretaceous/Tertiary (KT) Boundary. Possible locations include the San Juan Basin, NM.
5. Observe (from a safe distance) a river whose discharge is above bankful stage (I have watched a rather intense flash flood near Hillsboro, New Mexico, I don't know if that would qualify or not)
11. A slot canyon. Many of these amazing canyons are less than 3 feet wide and over 100 feet deep. They reside on the Colorado Plateau. Among the best are Antelope Canyon, Brimstone Canyon, Spooky Gulch and the Round Valley Draw.
14. A layered igneous intrusion, such as the Stillwater complex in Montana or the Skaergaard Complex in Eastern Greenland.
15. Coastlines along the leading and trailing edge of a tectonic plate (check out The Dynamic Earth - The Story of Plate Tectonics - an excellent website).
18. A field of glacial erratics
20. A sand dune more than 200 feet high
22. A recently formed fault scarp
23. A megabreccia
24. An actively accreting river delta
25. A natural bridge
27. A glacial outwash plain
28. A sea stack
29. A house-sized glacial erratic
30. An underground lake or river
31. The continental divide
32. Fluorescent and phosphorescent minerals
39. The Waterpocket Fold, Utah, to see well exposed folds on a massive scale.
40. The Banded Iron Formation, Michigan, to better appreciate the air you breathe.
44. Devil's Tower, northeastern Wyoming, to see a classic example of columnar jointing
46. Telescope Peak, in Death Valley National Park. From this spectacular summit you can look down onto the floor of Death Valley - 11,330 feet below.
50. The Goosenecks of the San Juan River, Utah, an impressive series of entrenched meanders.
51. Shiprock, New Mexico, to see a large volcanic neck
54. Mount St. Helens, Washington, to see the results of recent explosive volcanism.
59. The Mima Mounds near Olympia, Washington
61. The moving rocks of Racetrack Playa in Death Valley
64. The Burgess Shale in British Columbia
65. The Channeled Scablands of central Washington
66. Bryce Canyon
67. Grand Prismatic Spring at Yellowstone
68. Monument Valley
69. The San Andreas fault
75. A catastrophic mass wasting event
76. The giant crossbeds visible at Zion National Park
77. The black sand beaches in Hawaii (or the green sand-olivine beaches)
78. Barton Springs in Texas (will try to do that next time I am in Austin)
79. Hells Canyon in Idaho
82. Feel an earthquake with a magnitude greater than 5.0.
83. Find dinosaur footprints in situ
86. Find a meteorite fragment
87. Experience a volcanic ashfall
91. Witness a tornado firsthand. (Important rules of this game). (We were in our basement at 1 AM when we got hit by a tornado in 1998, it is probably not the same thing as watching one cross the plains of Oklahoma or Kansas)
92. Witness a meteor storm, a term used to describe a particularly intense (1000+ per minute) meteor shower
93. View Saturn and its moons through a respectable telescope.
94. See the Aurora borealis, otherwise known as the northern lights - (I was in Wisconsin in the summer of 1982, but I was enjoying the local beer and I forgot to look for the Northern Lights at night).
97. View a distant galaxy through a large telescope
98. Experience a hurricane
99. See noctilucent clouds
100. See the green flash

I would add a couple more things:

101. Go to the Crater of Diamonds State Park in Arkansas and stay there until you find a diamond. I found one my first trip there in 1973.
102. Stand on the platform of an operating oil drilling rig. I have sort of done this, we visited a couple of drill rigs in SE New Mexico on a Geology field trip in 1982, both were operating rigs, but they had suspended drilling for safety reasons while we were there (or else some maintenance was going on).

What a Geologist Sees - Part 26B [Original Post Date 2/25/09]

2011-01-17T23:06:00.003-05:00

Just a few more photos from my 1979 job in the Bisti Badlands of San Juan County, New Mexico.

The uppermost photo is from a clinker zone, which I may have explained in the previous post on this subject. It is basically baked shale from adjacent to a burned coal seam. On the left is a stem of some sort and on the right is a leaf fragment.

The second photo is of a permineralized (petrified) stump. I hope it somehow got hauled of to a museum or a geology department. It was way too heavy for me to move, though I would love to have something like this in my front yard.

The third photo is of one of the areas rich in permineralized logs. We were to collect samples from each of these and mark them on the map. I hope that the University of New Mexico gathered up these logs before the mine opened.

What a Geologist Sees - Part 26 [Original Post Date 2/10/09]

2011-01-17T23:00:00.002-05:00

Two years ago, I started a 30th anniversary recount of my life-changing move from the Atlanta area to El Paso. I got distracted and I don't think I got much past Fort Worth on I-20 in my story. I don't know if it is worth going back and picking up that thread.

This summer will mark the 30th anniversary of my 1979 summer job in the Bisti Badlands of San Juan County, New Mexico, a "few" miles south of Farmington.

It wasn't a field-mapping sort of summer job, it was a Fossil Recovery job. It was funded by Western Coal Company (a subsidiary of one or more utilities) in the "Four Corners" area and administered by UT El Paso and UNM. Per Federal and State law, before any significant land disturbances, a fossil recovery is required.

In the 440 mile trek from El Paso to Farmington, NM, I was leaving behind the wreckage of my first serious love affair (I was a late bloomer), just one of those life experiences that didn't turn out well. 'Nuff said.

When my field partner and I arrived at the work site, we were given our instructions on where to start and we were given our maps (which were the most-detailed, best topo maps a geologist could hope for). If my memory serves me, after 30 years, the scale may have been 1:100 with 5-foot contours, which made it very easy to figure out where you were, which was very important for the Fossil Recovery Project. One of our professors was there to start us off and he came up to check on us every couple of weeks or so.

We were in the San Juan Basin, working in the Cretaceous Fruitland Formation (Fm. abbreviation), to clear the area for a future coal mine. We were to sample and record the map locations of any occurrences of invertebrate fossils (fresh water clams) and permineralized (petrified) wood. When we found dinosaur bones (or other vertebrate fossils), we were to collect and bag all bone fragments and to record the map locations. For the larger fossils (as with the dino bone pictured here in both photos, from different angles), the Univ. of New Mexico would come in later and do their plaster-casting thing. Sometimes it would take two hours of being on my hands and knees to pick up every bone fragment. The idea was that the Univ. of New Mexico lab students would attempt to glue the fragments back together along with any larger pieces found nearby. Sort of like putting together a large jigsaw puzzle without a picture to guide you.

The environment of deposition of the Late Cretaceous Fruitland Fm. was somewhat similar to today's Everglades. The Fruitland Fm. was primarily composed of soft clays (which give rise to the "Badlands-type" topography), along with a few sandy stream channel deposits (which we would sample and screen for small vertebrate (rodent) teeth. It was from these channel deposits that we also collected the fresh-water clams.

After suffering through rain every day (except one) of the first two weeks, things settled down. The clays in the Fruitland Fm. are like grease when wet. So my field partner and I spent our time trapped in our respective truck campers, waiting out the rain. This is why I always stash books in my car trunk, in case I ever get stranded again, so I will at least have something to read.

One of the early things that I learned was that you always had to have your rock hammer with you, in case you slid into one of the ravines. They weren't terribly deep, but you couldn't get out unless you hacked crude stair steps into the clay, one at a time. Even when it was dry it was difficult to clamber out with the steps cut into the clay. You also had to use your rock hammer to pull yourself up the slope, by slamming the sharp, chisel end of the "shale pick" into the clay.

A couple of quick facts: 1) The "erosion pedestals" pictured in two of the photos were capped (protected) by hardened sandstone lenses or sometimes chunks of permineralized wood. 2) We covered about two and one-half square miles in 6 weeks (actually 4 weeks after the rain stopped).

We were supposed to go back there in 1980, but the area is a checkerboard of Federal and State land and each has their own permits and regulations that have to be reconciled before fossil collecting (recovery) is allowed. I am not sure if we were on Navajo Reservation land, or just close.

Aside from the dinosaur bones we found, we found fragments of large turtle shells (I was told by my professor that we might have found a new species of turtle), and crocodile "scutes" (bony plates).

On a side-note, as I didn't really get along with my field partner (our personalities were just different), he chose to hang out at the motel on our days off (Tues. and Wed.) and drink beer, while I drove up into Colorado and other places and drank beer there and took pictures.

Despite the fact that I enjoyed that summer job, I do have a few regrets from that adventure:

1) I should have talked my field partner into shifting our off days to Sat./Sun, so I could have hung out over at the Univ. of New Mexico Archeology field camp. There were a lot more female students in Archeology than there were in Geology at that time. Maybe I could have talked one of them into going with me on some four-wheeling/camping adventures in the mountains around Silverton or Durango, CO. (I had a 4X4 Jeep pickup with a camper shell).

2) I should have had a back-up 35mm camera when I went back to Arches National Monument. When I was there two years earlier, the shutter had jammed on my Miranda Sensorex II camera, though it somehow unjammed later (on the earlier trip in 1977). I got photos from Canyonlands and Mesa Verde, but none from Arches. I specifically drove back to Arches to get some photos and the same thing happened again (when it was happening, the operation of the camera sounded normal). So I have been to Arches National Monument twice and don't have a single photo to show for it. After the shutter jammed, I got no more slides for the summer.

3) I should have gone to Shiprock, AZ and maybe over towards Monument Valley (but then my camera might have betrayed me there, too).

4) My paycheck for the summer job was pretty decent in 1979. $2200 for six weeks - mid-May through June. But I didn't get paid until the end. The money, from Western Coal Co., was "funneled" through UT El Paso and that is where the checks were cut. They wouldn't mail them to me and they wouldn't let my professor bring them to me. I had to borrow money from my professor and from my parents and use credit cards to be able to travel at all. My biggest purchase (after I finally got my paychecks and after I paid everyone back) was a Pentax MX camera, to replace the aging Miranda.

5) I wanted to pan for gold in the Silverton, CO area, but because of a heavy snow melt, the creeks and rivers were full to the brim with muddy water. And because of the heavy snows, I couldn't get back into some of the back country areas in the San Juan Mts. until the last week of June, for photography and mineral collecting.

6) I should have picked up more "clinker zone" samples. When an underground coal seam burns (very slowly), it bakes the shales above and below the coal seam. We found a clinker zone of baked red shale with Cretaceous plant fossils (leaves and stems). I only picked up two pieces of the shale with plant fossils, I should have spent an hour there.

So it was an adventure of a lifetime, though it was smudged by the El Paso disappointments and the camera foul-ups.

Everything happens for a reason, even if we don't understand at the time.

I hope someday to return again and get some damn photos of Arches and then make a side trip to Monument Valley.

I will probably post a few more photos related to the project (I got a few hundred slides before the shutter crapped out). [Oh, I forgot to mention the story about my encounter with the redneck cop in Ouray, CO. That will have to wait.]

22 Different Drivers in the Driver's Seat [Originally Posted 2/4/2010]

2011-01-16T10:06:00.001-05:00

Climate Drivers are those inputs (influences) that affect the Earth's weather and climate, all are of different magnitudes and some (especially the first four) are on different cycles (or are subject to random events). Some of these cycles and drivers may exaggerate each other (Synergy) or they may partially (or wholly) cancel each other out (Antagonism).

Geologist H. Leighton Steward has produced a chart with 18 different climate drivers (or climate forcers). He acknowledges that there might be more and I have included several more myself.

After each listed Driver will be the Principle Influence, Impact, and Comments.

Solar Heat & Solar Magnetic Field - Solar heat and Magnetic shielding - Strongest - Heat retained by Earth influenced by other drivers. There are numerous solar cycles of different time intervals, that can affect quantity of heat, light, and magnetism being emitted by the Sun.
Orbital Eccentricity - Determines distance from Sun - Strong - Distance affects amount of solar heat received, influenced by gravitation pull of Saturn, Jupiter, and other planets.
Earth's Axial Tilt - Determines seasons and amount of heat received by higher latitudes - Strong - Additional tilt can affect polar ice melting (or growth).
Earth's Axial Wobble (precession) - Determines Earth's seasons closest to or farthest from the Sun, caused by the unequal distribution of land masses - Strong - Can be positive or negative feedback.
Water Vapor - Greatest quantity of all of the Greenhouse Gases - 90 - 95%, affects clouds, precipitation volumes, albedo, and vegetation, "thickens" the air - Strongest of Greenouse Gases - Highly variable, may not be included in computer models for this reason.
Water Droplets & Ice Crystals - As components of clouds, affects amount of visible light reaching the Earth's surface and traps rising heat from Earth's surface - Strong - Highly variable, may not be included in computer models for this reason.
Carbon Dioxide - Captures infrared heat rising from Earth's surface, reradiates some heat - Strong at low saturation - Generated by ocean releases, volcanic activity (including hot springs), animal/bacterial respiration, and combustion (natural and human), Greenhouse Effect non-linear, usually follows temperature changes, currently 0.0385%.
Methane - Captures infrared heat rising from Earth's surface, reradiates some heat - Moderate (low quantity in atmosphere) - Generated by wetlands, by animals, and industries, currently 0.00018%.
Ocean Currents - Distributes heat from Tropics to higher latitudes, can change quickly or slowly - Strong - Largest reservoir of surface heat.
Plate Tectonics (seafloor spreading) - Causes volcanism, releases carbon dioxide, sulfates, chlorine, and other gases, results in mountain uplifts, earthquakes - Strong, long-term - Affects position of continents, sea level, volcanic ash and sulfates affect atmospheric chemistry & atmospheric CO2.
Location of Continents - Affects major ocean currents and distribution of heat - Strong to weak - Land over poles increases glaciation, position of continents affects rising infrared heat from surface.
Elevation of Land Masses - Higher elevations promote glaciation and affect local wind currents; moderate elevations promote rainfall (through Orographic Uplift) & chemical weathering of rocks (see below) - Moderate - Affects regional climates, monsoons, and locations of deserts, especially North American deserts.
Chemical Weathering - Releases elements and compounds from minerals, affects chemistry of water bodies - Weak, long-term - Little short-term effect on climate.
Vulcanism - Constants sources of CO2, sulfates, ash particulates - Moderate to strong, short-term - May affect ocean chemistry, builds new islands, affects atmospheric chemistry.
Extraterrestrial Impacts - Immediate fires, then colder temperatures for a few years/decades - which affect plant communities and the food webs built thereon - Strong, very short-term - May affect atmospheric and oceanic chemistry.
Albedo - Determines amount of Solar Energy reflected or retained (absorbed) - Moderate to strong - Constantly changing, affected by other drivers.
Flora & Fauna (plants, animals, bacteria) - Affects albedo, oxygen, carbon dioxide, and methane content of atmosphere - Moderate - Terrestrial ecosystem diversity and richness affected by atmospheric moisture, temperature, and chemistry; Aquatic ecosystem diversity and richness affected by temperature, water energy, water chemistry.
Atmospheric Circulation - Vertical and Horizontal winds distribute heat and moisture and affect land surface and upper ocean circulation patterns - Moderate - Affects weather systems and distributes nutrients to oceans, affecting oceanic flora, fauna, and chemistry.
Cosmic Rays - Evidence suggests that cosmic rays produce particulates that seed low-level clouds - Impact to be determined - More research needed to determine impact.
Earth's Magnetic Field - May affect quantity of cosmic rays reaching the atmosphere - Impact to be determined - More research needed to determine impact.
Changes in Land-Use Patterns - Includes deforestation for logging and farming, growth of Urban Heat Islands, variable local and regional effects - Impact to be determined - More research needed to determine impact.
Carbon "Soot" and other Particulates - In some cases, particulates may reflect sunlight, in other cases they may absorb sunlight, may also serve as condensation nuclei for clouds and rainfall, some particulates are generated by combustion and human disturbances to the soil, i.e., farming, construction, and other human activities, in addition to natural sources - Impact to be determined - More research needed to determine impact.

My point here was to illustrate the complexity of the atmospheric interactions of these drivers (and any others yet-to-be-identified). In other words, it is a bit premature to say "the science is settled", as some political charlatans have said. Mother Nature is wild and we mere humans will never totally understand her.

The human influences on some of these could be ameliorated, but not if our economy (and the economies of other developed countries) are hobbled by unnecessary taxes and regulations, administered by un-elected bureaucrats driven by resentment of our freedom and prosperity.

A Lost Civilization Beneath the Waters of the Persian Gulf?

2011-01-08T11:58:00.009-05:00

From the website LiveScience.com comes this fascinating article concerning ancient Middle Eastern history and human culture.

[Image below courtesy of the above-linked article. Click here for an enlarged image of this map.]

From the article:

"Veiled beneath the Persian Gulf, a once-fertile landmass may have supported some of the earliest humans outside Africa some 75,000 to 100,000 years ago, a new review of research suggests.

At its peak, the floodplain now below the Gulf would have been about the size of Great Britain, and then shrank as water began to flood the area. Then, about 8,000 years ago, the land would have been swallowed up by the Indian Ocean, the review scientist said."...

In the article, the flooding of the fertile valley is attributed to rising sea levels following the end of the last major Pleistocene ice age. There is, however, another plausible event that may have contributed to the flooding of this valley - Plate Tectonics.

On the opposite side of the Arabian Plate from the Persian Gulf, lies the Red Sea, which is part of the East African Rift. The activity of the rift is pushing the Arabian Plate to the northeast, where it is colliding with the Eurasian Plate, uplifing the Zagros Mountains of Iran. Where you have the collision of two continental plates, it is common to have the uplift of a linear mountain range, e.g., the Himalayas. Adjacent and parallel to this mountain range is commonly a Foreland Basin, of which the Persian Gulf is an example.

[Image from the What On Earth blog.]

Continuing from the original article:

..."The Gulf Oasis would have been a shallow inland basin exposed from about 75,000 years ago until 8,000 years ago, forming the southern tip of the Fertile Crescent, according to historical sea-level records.

And it would have been an ideal refuge from the harsh deserts surrounding it, with fresh water supplied by the Tigris, Euphrates, Karun and Wadi Baton Rivers, as well as by upwelling springs, Rose said. And during the last ice age when conditions were at their driest, this basin would've been at its largest.

In fact, in recent years, archaeologists have turned up evidence of a wave of human settlements along the shores of the Gulf dating to about 7,500 years ago."...

Aside from the rising sea levels related to the post-Pleistocene ice-cap retreat, is possible that the gradual sinking of this Foreland Basin contributed to the flooding of the area.

Prior to this being a Foreland Basin, it was a part of the ancient Tethys Seaway - a Mesozoic - early Cenozoic seaway between portions of the separating supercontinent Pangea - as partially-described in a World Oil website post. [Scroll down to see Figure 4 and the text above the figure.]

From this World Oil post, in describing the geology behind the 151 giant oilfields in the region:

..."They are concentrated in a large foreland basin formed during the Late Cenozoic collision of the Arabian Peninsula with Eurasia. Downward flexure of the Arabian Peninsula beneath the Zagros Mountains of Iran/Iraq was caused by the northeastward consumption of the Tethys Ocean at the Zagros suture zone. Additional causes of this flexure were the eventual Cretaceous-recent convergence and collision of the Arabian plate against the Eurasian plate. This protracted convergent event has created the Persian Gulf and Mesopotanian [sic] lowlands as a sag in the foreland basin, as well as formation of the Zagros Mountains, with a culmination of fold-thrust deformation in Miocene and Pliocene time."...

It would be fascinating to read a detailed weaving-together of Old Testament Biblical History (and of other ancient texts) with geologically-recent Plate Tectonics events in the Middle East. Including the eruptions of Mt. Etna, Mt. Vesuvius, and the Santorini explosion/tsunami.

Returning to the second-cited source, the What on Earth blog, and the tectonic map, if you notice along the western edge of the Arabian Plate is a transform fault zone, which is the source of the Dead Sea Basin, as a very deep "pull-apart basin" (see the What on Earth January 29, 2009 post, same link).

But that is for another discussion.

A Follow-up to the Mineral Videos [Original Post Date 01/04/09]

2011-01-03T01:13:00.001-05:00

on minerals, just a few additional words on the subject to review clarify this issue for non-geologists (normal people). [Being on the road when those two videos were posted, I didn't have time to watch much of either, so if I repeat any of what was said, it is because what I wrote below is just part of my standard opening to the Physical Geology chapter on minerals.]

By definition, minerals are:

Naturally occurring, solid (at normal temperatures), inorganic (though they may be formed by organic processes), they have a definite chemical composition (or range), they have an orderly internal structure, and they have definite characteristics, e.g., crystal habit, cleavage, hardness, color (though color may be unreliable because of trace elements).

Minerals are important because they are the "building blocks of rocks". Most rocks are composed of two or more diffrent minerals, though there are a few rocks that are only composed of a single mineral, e.g., pure marble, pure quartzite, pure limestone...

Geology students generally learn to recognize individual minerals first, then they usually learn to recognize them in igneous rocks, as igneous rocks are the original source of most minerals, including the minerals that make up sedimentary and metamorphic rocks.

Some of the most common minerals that we come in contact with are salts - Halite (NaCl) being the most common of these and Sylvite (KCl) if you use Morton Lite Salt. There are other salts - potassium iodide (KI), etc. that are used for various reason in foods to deliver various trace elements that we need (or that enhance flavors).

Other minerals we encounter are quartz (the most common mineral on Earth), diamond (the hardest), perhaps some other gemstones, gypsum, and for anybody that still uses black-and-white camera film, some silver salts (I am clueless as to the chemistry of color film emulsions). [Sadly, IMHO, film photography is slipping further into history, which some folks will regret as digital images themselves are lost over time.]

BTW, for the beautiful crystals that some folks like to marvel over, for those nice crystals to form, they have to have "room to grow", perhaps into a fracture zone, or some other cavity or open space, or they were among the first minerals to crystallize in a cooling magma. Sometimes those growing crystals include (surround) other minerals as the crystal grows or in the case of gypsum (or other salts) in sediments associated with salt lakes, sometimes the crystals will include small rock fragments, sand grains, and other stuff.

Usually, geologists are not lucky enough to have good, well-shaped crystals for the purpose of identification. That is why we learn the other characteristics of individual minerals. There are high-tech ways of analyzing rocks, but they take time and cost money, so field geologists are still required to make a quick-and-dirty assessment of what minerals are present in a rock and uses the proportions of major minerals to define the rock itself.

[As I think of other examples, I may include them.]

Minerals - Part 2 of 6 [Original Post Date 12/30/2008]

2011-01-03T01:07:00.001-05:00

YouTube poster: mineguy101

Part 2 of a 1976 Series.

Mineral Video - Part 1 of 6 [Original Post Date 12/30/2008]

2011-01-03T01:04:00.002-05:00

From mineguy101.

This is part 1 of a 1976 series. If it is good, will add more.

What a Geologist Sees - Part 25 [Original Post Date 11/16/2008]

2011-01-03T00:56:00.001-05:00

Oh, the stuff we can see at construction sites and quarries!

[Disclaimer: I only enter construction sites on Sunday, when there is no activity, I stay away from the equipment and any obviously dangerous places and if there are any "No Trespassing" signs, then I don't go in.]

One "treat" at a construction site is to be able to see the effects of erosion and deposition in the exposed materials. In the uppermost photo, you can see the gulley erosion in the soft, graded soil. Just downslope from the gulley is a small "alluvial fan", where the eroded material was deposited. Larger examples of alluvial fans are seen at the mouths of mountain canyons.

In the second photo, in a sand pile at a quarry, as sand is removed from below, it triggers miniature slumps and landslides in an attempt to bring the slope back into equilibrium. In larger settings, slumps and landslides generally happen on slopes that have become destablized due to construction and heavy rainfall.

As one would expect, in a construction site, rocks are exposed that we usually wouldn't see at the surface. In the third photo, road construction has exposed a portion of a diabase (basalt) igneous dike that was most likely intruded during the Triassic or Jurassic Period. The iron-rich silicate minerals in the diabase are susceptible to weathering (by oxidation) in this humid climate, thus these blocks from the shallow sub-surface show a "rind" of oxidized material, with fresher rock material within the block.

In the fourth photo, we see "saprolite" that has been exposed during the construction of a drugstore. Saprolite is called "rotten rock" by some, it is rock that has been chemically weathered to the point that its structural integrity has been lost and the material can be easily crushed by hand. The "parent rock" - exposed nearby - is a biotite gneiss, similar to a granite, and in the case of the saprolite, the feldspars, micas, and other minerals (except for quartz) have been altered to clays. If not covered over quickly, this sort of material would wash into a nearby creek, resulting in "silting up" of the stream (and a probable EPA/Ga EPD fine).

The fifth photo, of another sand pile, shows how gravity, with the help of the wind, attempts to stablize the slope of this sand pile. Unconsolidated (loose) materials have a defined "angle of repose", which is the maximum angle-of-slope that particular sized material can sustain. If a slope is "oversteepened", miniature landslides and slumps carry material downslope in an "attempt" to establish equilibrium at the angle of repose, which generally varies between 25 and 35 degrees, depending on the size and angularity of the particles.

In the final photo, in this pile of mixed sand and gravel, rainfall has induced "rill erosion" (small erosion channels) on the slopes and small alluvial fans at the base of the slope.

[All of these photos were taken in the greater Atlanta area.]

In Geology, we term the mass downslope movement of material to be "mass wasting". [Yeah, I know Geologists can get mass-wasted after too many adult beverages, but that is another story.] Mass wasting occurs when gravity overcomes cohesion and internal friction. Water can be a facilitator of this process, as well as earthquake, traffic, and construction vibrations (as suggested above).

What a Geologist Sees - Part 24b [Original Post Date 10/31/2008]

2011-01-03T00:52:00.001-05:00

Just a couple of photos from the City of Rocks State Park in Grant Co., NM, as referenced in the previous post. It is a neat place to camp, but one time I stopped there at night to show it to a friend as we were traveling through the area. In the moonlight, the "hoodoos" were just a little too spooky.

If memory serves me correctly, these pyroclastic ash flow tuffs were erupted from the very large Emory Caldera.

What a Geologist Sees - Part 24 [Original Post Date 10/31/08]

2010-12-17T07:51:00.001-05:00

I am sure that many folks have seen rounded boulders before. Have you given much thought to how they got rounded?

One possibility is that the boulders were rounded in a river channel subject to "big ass" floods, necessary to move and abraid the boulders against each other.

But more often, the boulders are rounded in situ (in place) by a process called spheroidal weathering. On the Georgia Piedmont, most often we see spheroidal weathering in granites and granitic gneisses.

A couple of other places where I have seen spheroidal weathering of granites is Texas Canyon, AZ and Sequoia National Park. [While traveling with my college roommate Dave in 1974, we were in our campsite in Sequoia, stretched out on the hood of the car, leaning against the windshield watching the stars. In the dim light of nearby lanterns, we could see that we were surrounded by rounded granite boulders. After a while, I became aware that there seemed to be an "extra boulder". Turning on the flashlight, that "extra boulder" stood up (it was a bear). At that point, we decided the car was a better place to sleep that night, rather than the tent.]

An additional place where I have seen spheroidal weathering, of volcanic ash-flow tuffs, is in the City of Rocks State Park in New Mexico. [I may place a photo in a later post of this particular place.] With the softer ash-flow tuffs, wind erosion may have also played a role in rounding the boulders, in that particular locale.

What is destined to become rounded boulders starts off as fractured bedrock, broken by what we call brittle deformation. At depth, with the greater confining pressure and heat, rocks become plastic (softened) and undergo folding, stretching, and other forms of ductile deformation. At shallower depths, without the confining pressure and the flexibility provided by the higher temperatures, the rocks become fractured and jointed during earthquakes and other heavings of the earth, leaving angular corners.

As weathering and erosion proceed over the countless millenia, the downward percolating water and natural acids attack the minerals on the outer margins of the rock, by way of the joints and fractures - in the shallow subsurface. The chemical breakdown of minerals by chemical reactions is called chemical weathering.
There are several chemical weathering processes, the one that attacks the feldspars in the granites is primarily hydrolysis.

In areas prone to occasional freezing, the expansion of ice in the fractures (and microfractures) provide even more surface area. This is one process in what we call physical weathering.

Over time, the combined processes of physical and chemical weathering attack the corners of the rock, rounding them off. As erosion carries away overlying soil and degraded rock, the boulders become exposed, wherein the processes of chemical and physical weathering continue, yielding the rounded boulders as seen in the photo.

[The scars seen on the photos are likely from the bulldozers used to "gather" the boulders during construction at the nearby Nature Center parking lot.]

[Visit this post for links to previous posts in this series.]

What a Geologist Sees - Part 23 [Original Post Date 10/10/08]

2010-12-17T07:47:00.001-05:00

Providence Canyons, locally called "the Little Grand Canyon", in Stewart County, Georgia, provides a stark look at what can happen when erosion takes hold in an area underlain by a soft sand.

The canyons are generally on the order of 125 feet deep and are only perhaps 150 years old.

The supposed genesis of the canyons was due to rain running off the corner of a church and beginning a small gully. The surface of this area is locally covered by the residuum of the Paleocene-aged Clayton Limestone, which has been reduced to a iron-rich, reddish clay. One this clay veneer is breached by a gully, the underlying soft, deltaic sands of the Cretaceous Providence Sand. There is essentially nothing to stop the downward erosion or the widening of side canyons. At some point in the future, the area will probably reach some sort of equilibrium as a series of low sandy hills, separated by sand-clogged, braided streams.

As an aside, exposures of sand such as this serve as "recharge zones" for sand aquifers and elsewhere, the subsurface Providence Sand does serve as an aquifer.

[Older posts in this series, before Part 22, are linked here.]

What a Geologist Sees - Part 22 [Original Post Date 10/10/08]

2010-12-15T04:59:00.002-05:00

Most folks know a river or creek meander when they see one (or more).

Usually we see them in Coastal Plain settings or other places where the stream gradient (feet/mile drop in elevation) is low, especially if the materials underlying the stream are soft Coastal Plain sediments and/or floodplain deposits.

When a stream's gradient is steep, as in a mountain stream, there is a tendency for gravity to control erosion, i.e., the erosion is vertical - down-cutting as we call it. This vertical down-dutting (being slightly redundant) results in sharp "V"-shaped valleys, with no flood plains.

So when you see deeply-incised meanders, such as in the above photo, that suggests that the meanders were established under low-gradient conditions at a higher Base Level (see this post for an explanation of Base Level). Then a rapid drop in Base Level and/or a rapid uplift of the land "preserved" the meanders as the river cut downward through the Colorado Plateau sedimentary rock layers.

The Grand Canyon also illustrates this same rapid uplift/drop in Base Level, as does the area containing the Black Canyon of the Gunnison River, in Colorado, though without the meanders.

[Previous posts in this series are linked here.]

What a Geologist Sees - Part 21 [Original Post Date 9/05/08]

2010-12-15T04:56:00.001-05:00

Understanding the concept of Base Level is an important part of understanding the behavior of streams, erosion, and subaerial (terrestrial) stream deposition.

"Base Level" (mentioned briefly here) as a concept was defined by John Wesley Powell and is the lowest point to which a stream can erode at any one point. More info is presented here.

Ultimate Base Level is Mean Sea Level, i.e., rivers and streams cannot erode any deeper than sea level.

Over geologic time, Ultimate Base Level changes with changes in sea level. The primary causes of Mean Sea Level are variations in polar icecap coverage (more ice = lower sea level) and variations in plate-tectonics oceanic rift zone activity. When rift zones are more active, the sea floor is bulged upwards by the rising mantle plumes, which displaces sea water and raises sea level. When rift zone activity slows, sea level drops. Add to this local changes in the elevation of continental margins. When the edge of a continent rises, that mimics a sea level drop (aka a Regression) and vice versa when the edge of a continent sinks, that mimics a sea level rise (aka a Transgression).

When the Ultimate Base Level rises, the "Ultimate Stream Gradient" (from the ultimate stream/river source) is decreased, resulting in more deposition. There will be deposition also in any "drowned" portions of previously exposed river systems. When Ultimate Base Level drops, the Ultimate Stream Gradient increases (steepens), resulting in more erosion.

Within every river and creek system, there are inumerable "Local Base Levels", points below which the upstream river (or creek) cannot erode. Local Base Level controls the upstream-gradient on that particular river/creek until the next higher-elevation Local Base Level.

In the second photo, there is a small example of a Local Base Level, established by this small outrcop in Chickamauga Battlefield Park. Upstream from this locally resistant outcrop, the stream is prevented from down-cutting any further. The next ledge or other outcrop upstream then establishes the next upstream Local Base Level.

As changes in sea level affect the Ultimate Base Level and the Ultimate Gradient, changes in a Local Base Level affects Local Stream Gradients. When a dam is constructed (or when a landslide naturally forms a pond/lake), that raises the Local Base Level, resulting in more deposition. When Lake Lanier was constructed a little more than 50 years ago, the rising "pool elevation" raised the Local Base Level of all streams entering the lake. In the upper photo, you see the exposed lake-bottom sediments, contributed by local hillside erosion and by deposition of sediments contributioned by this particular small stream, over the course of 50 years.

When the extended drought and dam releases caused a lowering of the pool elevation, that lowered the Local Base Level and resulted in the few inches of erosion (down-cutting) that you see in the upper photo. When the lake returns to its Full-Pool elevation, the upstream Local Base Levels will again rise and down-cutting will cease and sedimentation will resume.

There are characteristic stream behaviors that are affected by the steepness of the stream gradient (Ultimate and Local). When you have a steep gradient (low Ultimate Base Level or Local Base Level), you have more down-cutting in the stream valleys. When the Base Level suddenly rises, the upstream valleys are "back-filled". Remember, a subsidence of a continental margin can mimic a Base Level rise.

On Coastal Plains and River Deltas, where the gradient is very low, lateral erosion causes migration of the stream channels and the resulting meanders. And usually in this situation, you have wide floodplains and/or local low-relief topography. When you have a low-gradient feature, such as river meanders, in an area with great topographic relief, that can tell you of a rapid drop in Ultimate Base Level or a rapid uplift of the landmass, such as with the Colorado Plateau (discussed in the next post of this series) or with some other regional feature, such as the land surrounding the Black Canyon of the Gunnison River, in Colorado.

Changes in Local Base Level (including some caused by human activities) can have smaller scale effects on local streams (as decsribed above regarding Lake Lanier).

[Previous posts are linked here.]

Minerals That I Would Like to Collect [Original Post Date 8/22/08]

2010-12-15T04:53:00.002-05:00

[Yeah, this would only appeal to the occasional geologist visitor.]

Having been involved with Geology for more than 35 years, there are a few minerals that I would like the experience of having "dug" myself or at least to have found them on a mine dump. Some of these I do own specimens of, having bought them or traded for them. But I would like the "wow" experience of having found at least a recognizable specimen, by my own hand.

In no specific order, they are:

1) Topaz - it has been reported from Graves Mt., GA and I have a mystery crystal from that locality that I would like for someone to verify, yes or no.
2) Garnets - with good crystal faces, at least 3/8 inch in diameter.
3) Biotite mica - some thin "books", at least 2 inches by 2 inches square.
4) Millerite - a fibrous nickel sulfide, found in small geodes near Halls Gap, KY.
5) Zircon - a decent crystal, at least 3/8 inch on any particular side.
6) Brookite - a titanium dioxide mineral from Magnet Cove, AR.
7) Wulfenite - have a number of purchased crystal specimens, would like to find one.
8) Apatite - a decent, recognizable crystal. I think I have some small apatite crystals in marble from Tate, GA and in some pegmatite material from Maine, but they are all in matrix.
9) Lazulite - some decent crystals from Graves Mt., GA. I have some weathered and broken specimens, but no decent ones.
10) Spodumene - a lithium silicate, I have been to one locality in NC, but didn't find any.
11) Selenite (gypsum) - from Jet, OK, for instance. I have found gypsum in several localities, but not any decent crystals.
12) Barite - crystals from Cartersville, GA. I have barite crystals collected from Graves Mt., and the Bishop Cap Hills in southern New Mexico. But I have missed field trip opportunities for the Cartersville area.
13) Vivianite - a nickel phosphate. Some small masses of vivianite have been found inside of fossil oyster shells on the Georgia Coastal Plain, near Providence Canyons. The vivianite was deposited inside the shells by groundwater action.
14) Talc - just some decent, light colored masses of the mineral, not the metamorphic rock (which I already have).
15) Epidote - just a decent sized, 1/2 inch length or longer crystal. I have smaller crystals, but not big enough for non-collectors to appreciate.

What a Geologist Sees - The Series - Phase 2 [Original Post Date 8/18/08]

2010-12-15T04:48:00.001-05:00

Phase 1 is indexed here.

Part 11 - Appalachian/Cumberland Plateau, limestone, Silurian fossils
Part 12 - Georgia Coastal Plain, water well construction
Part 13 - Southern New Mexico Quaternary Volcanics, Kilbourne's Hole, base-surge deposits
Part 14 - Southern New Mexico Quaternary Volcanics, Kilbourne's Hole, volcanic bombs, xenoliths
Part 15 - Xenoliths & other rock inclusions
Part 16 - Industrial uses of mica
Part 17 - Florida Coastline, external sedimentary structures, ripple marks, raindrop impressions
Part 18 - Southern New Mexico Quaternary Volcanics, Aden Basalt features
Part 19 - Glacier National Park, structural geology, thrust faults
Part 20 - Colorado Plateau, Monument Valley, sedimentary layers

What a Geologist Sees - Part 20 [Original Post Date 8/18/08]

2010-12-15T04:30:00.003-05:00

[As referenced here, Stratigraphy is the study of layered rocks.]

Monument Valley, which straddles the AZ/UT border, is one of those places on my Top-10 Want-to-Visit List (which will be the subject of a later post).

In the course of my classes, whether they be Environmental Science or Geology, I remind my students that in the future, if they do a little "homework" before traveling, they will enjoy the trip more. Especially if they have kids to entertain.

To a non-scientist, it might seem that thinking about the geology might distract from the enjoyment of the natural and stark beauty, but to me it doesn't. To me, visualizing about "what it used to look like" at various points in geologic history adds to the wonder. To address the subject of the first photo (actually all three slides were taken by my Dad in 1980), the mesas, buttes, and most of the spires of Monument Valley are remnants of a formerly-continuous sheet of Permian and Triassic sedimentary rocks. The millions of years of weathering and erosion have brought forth the wonderous landforms we see, not only in Monument Valley, but elsewhere in the Colorado Plateau.

The four formations shown in the second photo are but a small portion of the "Colorado Plateau Stratigraphic Section", i.e., all of the layered rocks that occur within the defined area of the Colorado Plateau. [This USGS webpage lists all of the geologic units that occur within the Colorado Plateau, some of which only occur at the margins and extend into adjacent regions. This USGS webpage lists all of the National Parks and such that are present within the Colorado Plateau (and the Colorado River Basin). Monument Valley itself is not administered by the National Park Service.] A simple geographic definition of the Colorado Plateau, which covers 50,000 square miles, is presented here by Encarta. The Moenkopi and Organ Rock Formations are present to the north at Canyonlands National Park, while the de Chelly Sandstone is present to the south at Canyon de Chelly National Park. The Permian de Chelly Sandstone is derived from eolian sand-dune deposits. At Canyonlands, the White Rim Sandstone lies between the Moenkopi and the Organ Rock, thus making it the "Stratigraphic Equivalent" of the de Chelly, though the environment of deposition was different, suggested to be nearshore sand dunes for the White Rim.

In arid climates, topographic slopes are often defined by their underlying rock types in ways that are different from humid climates. The contrast between arid-climate "slope formers" and "cliff formers" is illustrated by the mesa (I think it is Sentinel Mesa) in the second photo. In arid climates, shales are "slope formers", while sandstones and limestones are "cliff formers". Alternating shales and sandstones/limestones produces a "stair-step effect", with the slope angle related to the percentage of shale vs. the other two rock types.

[I can give a more detailed description of why limestones behave differently in the contrasting climates, but that would take up more space.]

The third photo is of Agathla Peak, which is different from the other landforms in Monument Valley. It is an eroded "volcano neck", i.e., the central spire represents solidified magma within and/or below the original volcano. It is more resistant to erosion than the slope material that made up the flanks of the volcano. The volcano neck can also be referred to as a "feeder pipe". Shiprock is another good example of this type of landform. Agathla Peak is some 1,500 feet higher than the surrounding plateau.

[Additional info may be added later.]

What a Geologist Sees - Part 19 [Original Post Date 6/08/08]

2010-12-15T04:23:00.002-05:00

Glacier National Park is one of the places that I hope to visit, someday.

[For the moment, a photo taken by a friend will have to suffice until I can get there to take my own.]

The feature pictured at right is Chief Mountain, which consists of Proterozoic limestones sitting atop Cretaceous shale and sandstones. This is totally "out-of-whack" with "what should be". Under normal conditions, the Concept of Superposition applies, wherein in a series of layered rocks (usually sedimentary, but could apply to some volcanics), the oldest layers are at the bottom and the youngest are at the top. The Proterozoic is much older than the Cretaceous.

The presence of a "thrust fault" is the reason for the existing condition. During periods of tectonic deformation, where there is lateral compression, sometimes sheets of rock will break loose and get "shoved on top of" younger layers. The lateral breakage is usually along a shale layer. In this case, the thrust fault is referred to as the Lewis Thrust Fault or the Lewis Overthrust. Erosion after the period of faulting isolated Chief Mt. from the remainder of the thrust sheet, thus we call Chief Mt. a "klippe", which is a type of "erosional outlier", i.e., it is laterally separated from similar rocks.

The mesas and buttes of Monument Valley are also erosional outliers, but they have no underlying thrust fault, so they are not klippes.

There are plenty of thrust faults in the Appalachians, including the Georgia Piedmont, though they are obscured by soil and vegetation cover. There is a thrust fault (name forgotten) exposed in an outcrop on the west side of I-285, north of the intersection with I-20 and near the Chattahoochee River, but the traffic makes it difficult to pull over and get a good photo.

[I will fill in some more details later...]

Learning Something New...Every Day (Well Almost)

2010-12-12T09:02:00.003-05:00

From the well-known geoblog "Highly Allochthonous", comes a post (from a few months ago) about a recent 5.0 earthquake in eastern Canada.

Scrolling through the post, I learned that the St. Lawrence River follows a small graben system, related to a failed rift-system related to the rifting of the supercontinent Rodinia and the opening of the Iapetus Ocean, about 1 billion years ago.

Similar to the New Madrid Fault System along the Mississippi River, crustal weaknesses due to the old breaks make the area susceptible to earthquakes.

[When time permits, I plan to write a bit more about this newly discovered (from my perspective) geologic feature.]

What a Geologist Sees - Part 18 [Original Post Date 5/06/08]

2010-12-12T08:52:00.001-05:00

Is this the world's smallest volcano? Maybe. [See the rock hammer for scale.]

This is a small example of a volcanic spatter vent. Usually spatter vents are late-stage events in the life cycle of an eruption, as the volcano is "losing its punch."

This spatter vent and the spatter mound shown below are just a couple of small, yet interesting features of the Aden Basalt Flows, which are part of the Potrillo Volcanic Field in southern Doña Ana County, New Mexico. The cinder cones of the northern parts of the Potrillo Volcanic Field are visible to the south of I-10, west of Las Cruces, New Mexico. Kilbourne's Hole, discussed in What a Geologist Sees - Part 13, is also part of the Potrillo Volcanic Field.

Most of the Aden Basalt flows are the result of fissure eruptions (lava flows erupted from open fractures in the ground surface), except in the northwestern part of the Aden Basalts, where Aden Crater (a small shield volcano) is present. Aden Crater is thought to have formed after the bulk of the fissure eruptions. Aden Crater (the subject of a future post) lies at the probable intersection of the Robledo Fault and the Aden Volcanic Rift (a buried fracture zone).

Spatter vents erupt by spitting small to moderate clots of partially solidified basalt (of the consistency of taffy).

The lower photo is of a mound of spatter material within Aden Crater itself. The stadia rod (used in mapping), leaning against the right side of the spatter mound, is about 6 feet long (for scale).

These are just a few of the many interesting volcanic features to be found in the Aden Basalts. Many typical features of basaltic vulcanism are preserved in the Potrillo Volcanic Field, along with some oddities that have not been seen elsewhere (for another post).

In another future post, I will show some different types of volcanic "ejecta" (aka volcanic bombs), which are found associated with some of the volcanoes of the Potrillo Volcanic Field. Just a suggestion, if you ever drive out into this area, carry plenty of water, have a good map, and let someone know where you are going.