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

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".

For Any Visitors...

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]

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

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]

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]

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]

...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 26B [Original Post Date 2/25/09]

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.

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

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.

1. 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.
2. Orbital Eccentricity - Determines distance from Sun - Strong - Distance affects amount of solar heat received, influenced by gravitation pull of Saturn, Jupiter, and other planets.
3. Earth's Axial Tilt - Determines seasons and amount of heat received by higher latitudes - Strong - Additional tilt can affect polar ice melting (or growth).
4. 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.
5. 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.
6. 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.
7. 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%.
8. 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%.
9. Ocean Currents - Distributes heat from Tropics to higher latitudes, can change quickly or slowly - Strong - Largest reservoir of surface heat.
10. 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.
11. 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.
12. 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.
13. Chemical Weathering - Releases elements and compounds from minerals, affects chemistry of water bodies - Weak, long-term - Little short-term effect on climate.
14. Vulcanism - Constants sources of CO2, sulfates, ash particulates - Moderate to strong, short-term - May affect ocean chemistry, builds new islands, affects atmospheric chemistry.
15. 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.
16. Albedo - Determines amount of Solar Energy reflected or retained (absorbed) - Moderate to strong - Constantly changing, affected by other drivers.
17. 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.
18. 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.
19. Cosmic Rays - Evidence suggests that cosmic rays produce particulates that seed low-level clouds - Impact to be determined - More research needed to determine impact.
20. Earth's Magnetic Field - May affect quantity of cosmic rays reaching the atmosphere - Impact to be determined - More research needed to determine impact.
21. 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.
22. 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?

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]

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]

YouTube poster: mineguy101

Part 2 of a 1976 Series.

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

From mineguy101.

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

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

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.