Get Your Kicks on Route 666 - Part 2

 Part 1 of this post was a time-lapse video, southbound on U.S. Hwy 491 (old U.S. Hwy. 666). [Not my video.]

My journey was a continuation of Day 6 of 2015 Arizona Trip #2, the day I left Albuquerque on the way back to Phoenix to visit my daughter's family again (by way of the "scenic route").

On this day, July 19, 2015, I was northbound on U.S. 491, with the intent of revisiting and photographing Shiprock, which I had briefly seen on a field camp field trip in 1977 (while my camera was messed up) and on 2015 Arizona Trip #1, during which time it was shrouded in low-hanging clouds.  

[As shown on "Google Maps/Street View", shortly after leaving I-40, outside of a McDonalds in Gallup, one sees a U.S. 491 sign, with a "Former U.S. 666" sign below.  Personally, my first acquaintance with U.S. 666 was after I moved to El Paso in January 1977.  

A few weeks after settling in for grad school at UT El Paso, I drove to Phoenix to visit my aunt and uncle.  A few miles before I reached Wilcox, AZ on I-10, I noticed the exit for U.S. 666 North.  It was a minor "Wow" moment.  That section of U.S. 666 later became U.S. 191.]  

As I proceeded north on U.S. 491, I was unaware of the other "eroded volcanic necks" in the area, nor the definition of the Navajo Volcanic Field.  [After becoming familiar with tthe Navajo Volcanic Field, from my observations, it seems to have the greatest concentration of eroded volcanic necks, in the country.]

Geologist James St. John has an excellent collection of volcanic neck photos on his flickr site, as well as having accompanying descriptions, too. According to St. John's description (based upon Delaney, 1987), the Navajo Volcanic Field, located in the "Four Corners Region" consists of approximately 80 eroded volcanic centers (necks, plugs, diatremes, and associated dikes) and is of Oligocene to Miocene age.  Shiprock itself is estimated at 32 to 27 million years in age.

When I got in the vicinity of Mile Marker (MM) 60 or so, I noticed a couple of "bumps" ahead, one on each side of the highway.  As I neared MM 64, I was greeted with a "Wow moment" on each side of the highway.  

Figure 1.  Bennett Peak (west side of U.S. 491), near Tocito, San Juan County, NM

[As you can see, the sky was partly to mostly cloudy, resulting in subdued lighting along old U.S. 666, but I was glad to be there and glad to be having the experience of all of these geologic "surprises".]

This is the larger of the two volcanic necks at this site.  On the other side of the highway was Ford Butte (Figure 2).

Figure 2.  Ford Butte (east of highway).

With an "eye on the clock", I got out and shot photos of both, figuring I would identify them later.   

At about MM 70, ahead I started seeing Shiprock on the left, an unnamed mesa in the "center view" and a smaller "bump" and a low ridge on the right.  As I proceeded, they all came into a greater view.  Getting to MM 77, the mesa on the left (west) was larger than expected and composed of sedimentary rocks (judging by the layering).  I later learned that this was "Table Mesa" (Figure 3) (which is sort of redundant, as "mesa" means "table" in Spanish).

   

 Figure 3.  Table Mesa.  (an educated guess would be Mesa Verde Group over Mancos Shale, until I determine otherwise.) 

To the right (east) of the highway was Barber Peak (Figure 4).  Further off to the east was a low ridge, called "Hogback Ridge". 

 Figure 4.  Barber Peak eroded volcanic neck (east of U.S. 491) at approximately MM 78.

By MM 78, another feature, behind Table Mesa had "popped up" on the left, known as "Cathedral Cliff", another presumed eroded volcanic neck and the view was better at about MM 79.

Figure 5.  "Cathedral Cliff", between MM 79 and MM 80.

Just before MM 85, is the left turn (onto Red Rock Hwy.) that leads to the south side of Shiprock itself, my intended target for the day.  Once on Red Rock Hwy., I didn't care about the mileage, as I could see Shiprock easily.  As I didn't know how close the highway came to Shiprock itself, I stopped several times, in case that was "as close as I could get".  From my Physical Geology Lab books, I was familiar with the radial dike that extended roughly due South from the core of Shiprock, I was hoping to get a good look at that feature, also.

In a few minutes, my wishes were granted.

[More info in Shiprock is presented here.]

 Figure 6.  Shiprock's "southern dike", composed of a dark, finely-crystalline minette, a type of Lamprophyre.

 Figure 7.  Without having a bright, sunny day available, this was about the best view I could get, with my longer camera lens.  But it was still magnificent.

In its position overlooking the San Juan River (a few miles to the north) and its distinctive shape and size, Shiprock has been a landmark used by travelers for centuries.  The Navajo name for Shiprock is "Tsé bit’a’í" ("rock with wings"). 

 Figure 8.  A direct view of the exposure of the southern dike, at Red Rock Hwy.

Figure 9.  A magnificent oblique view of the southern dike, showing the effects of "Differential Weathering", between the dike and the (presumed) Mancos Shale "host rock".

In James St. John's comments, he suggests that there as been an estimated 1 to 2.5 km of erosion of the original terrain, since the eruptions.

There was a barbed-wire fence parallel to the highway and a dirt road parallel to the east side of the dike.  There was an open gap in the fence and no "No Trespassing" signs.  It was so tempting to drive in, but I wanted to be respectful of the Navajo Nation and its laws and customs.  So I abstained from any entry.

As I planned to reach Aztec, New Mexico before dark, I couldn't spare much more time, but I did manage to get another photo of a Navajo Volcanic Field feature, west of Shiprock, called "Mitten Rock" (Figure 10).  James St. John has a much better photo of Mitten Rock.

Figure 10.  Mitten Rock, north side of Red Rock Hwy.

From there, I returned to U.S. Hwy 491 (old U.S. 666) and continued northbound.  Within the vicinity of Barber Peak (east of the highway), there were a couple more small, unnamed eroded volcanic centers (Figures 11 and 12).

 Figure 11.

Figure 12.

From there, I continued on north to the city of Shiprock, then turned east in U.S. Hwy 64 and headed east towards my final destination of Aztec, New Mexico.  I did stop for late-afternoon shots of the Farmington Monocline and the nearby river terraces before getting to the Presidential Inn & Suites and then returning to Farmington for dinner.  

It had been a full day and tomorrow promised the same, from Aztec, NM to Durango, CO for photos and a beer stop, then west to Cortez, CO, then to Monument Valley, and then to Flagstaff.  I had only driven 265 miles or so on Day 6, but the hundreds of photos made the day so much fuller.

References

Chronic, H. (1987), Roadside Geology of New Mexico.  Mountain Press Publishing Company.

Delaney (1987) Ship Rock, New Mexico: the vent of a violent volcanic eruption. Rocky Mountain Section of the Geological Society of America, Centennial Field Guide 2: 411-415.

Semken, S. 2003. Black rocks protruding up: the Navajo Volcanic Field. New Mexico Geological Society Guidebook, 54th Field Conference, September 24-27, 2003: 133-138. (semken.asu.edu/pubs/semken03_nvf.pdf)