Back on US191, we sped North back toward I-70. After you pass the Moab airport, all the cliffs and domes and faults and anticlines and all the rest of the geo-drama is left behind, and the road is lined by endless, dull gray scrubby rolling plain. Even the “scrub” is sparse; mostly what you see is a lot of gray dirt. This is the layer above* the Morrison formation, the Mancos Shale.
*In many areas, there are 1 or 2 more narrow formations in between the Morrison and the Mancos: the Cedar Mountain and Dakota Sandstone formations.
Unlike so many of the Utah geologic formations we’ve looked at so far, Mancos doesn’t form any cliffs or smooth waves or arches or alcoves. It doesn’t form spires or bridges or slot canyons. It isn’t the centerpiece of any national or state park, monument. And yet, you probably see more of it driving around Central and Southern Utah than you do any other formation.
Part of this is because there’s so much of it. Mancos is a mudstone, laid down in shallow seas during the Cretaceous, and in many places it lies a few thousand feet thick. But the other reason is that many roads tend to follow it. Mancos doesn’t form any of those spectacular features because it erodes so easily, and quickly comes to rest in broad, gently undulating lowlands, perfect for routing a highway. If you drive from the Colorado border to Price, UT, you’re on Mancos the whole way.
Once you get off the asphalt, Mancos is both wonderful and horrible. In dry conditions, graded dirt roads across the Mancos are often smooth and fast, allowing a passenger car to zip comfortably along at 40 or 50 MPH. But when wet, forget it. Mancos roads become a thick, gloopy stew that’ll quickly snare your 4WD vehicle.
Extra Detail: Often times when you’re tooling along some Mancos track you’ll see deep tire ruts left over from someone drove the wet road. If you check out the deep ruts, you’ll often see that they have marks from tire chains, which is how the ranchers get through when it’s wet. I used to carry around tire chains in my old pickup for just this reason, but eventually decided it was just less hassle to stay off Mancos/clay roads when potentially wet.
I always find Mancos a bit un-nerving, partly because I’ve encountered it wet, but also because it seems so bleak, and borderline lifeless. Why so few plants? This part of the state is dry for sure, but other nearby soil types generally don’t look so bleak. Another reason is the high concentrations of selenium in Mancos soils*, which are problematic for many plants. But probably the most important reason is that Mancos is an expanding clay**, which increases its volume dramatically when wet. The frequent moisture-induced expansions and contractions of the Mancos make it very tough for seedlings to gain a toehold in the soil.***
*I covered selenium content in soils, plants and people in this post.
**I covered expanding clays in this post.
***And now that I think of it, I don’t think I’ve ever seen fully developed cryptobiotic soil on Mancos. (Though maybe I just haven’t looked hard enough.) I covered cryptobiotic desert soils in this post. Man, it is like I have a post for everything.
As you approach I-70, you’ll see a massive wall of high, beige cliffs on the North side of the freeway. These are the Book Cliffs, formed from the Mesaverde formation, layers of sandstones interspersed with shales and limestones.
I’ve driven past and along the Book Cliffs (pic left) probably a couple of hundred times. Embarrassingly, with the exception of a few quick forays over a decade ago in Colorado, I haven’t explored the area at all. And what’s interesting, is that with the exception of a few hunter-friends, practically no one I know in Utah has spent any time in the Book Cliffs. The reason is that because Utah has so many more spectacular places to visit, hardly any of us bother with the area. It’s part of the Utah irony: this state has so many amazing features which if you picked up and transported to say Michigan or Nebraska, would totally merit national park status. But here in Utah, we don’t even really notice them. That’s a shame, because when it comes to the Book Cliffs, there are at least 3 really cool things about them.
Tangent: Thinking about the Book Cliffs got me noodling about the broader issue of geographic blanks spots. By blank spots in this case, I’m not talking so much about faraway places I’ve never been to, say like Madagascar or New Caledonia, but places I’ve been right by over and over again, but never checked out. The Book Cliffs are one example. Another is- or rather was- Jack’s Peak*, until the Trifecta and I climbed it this Spring. The Canyon Range West of Scipio, the Pine Valley Range North of St. George, the Uintas West of Mt. Agassiz- all are blank spots on my mental map of Utah. Closer to home there are still dozens of draws and minor peaks in the Wasatch and Oquirrhs I’ve yet to explore, and even within 2 or 3 miles of my home there are side streets I’ve never turned down. As you think about your own home “turf”, it’s likely you can think of similar blank spots that you’ve passed by time and again for years or even decades without checking out.
*Speaking of Jack’s Peak, Since I’ve become (at least marginally) geologically-aware, I’ve learned that the peak, and the ridge leading up to it, is actually its own little anticline.
Nested Tangent: When I think about blank spots, I tend to construct an image of them in my head- how the landscape looks, the vegetation, the aspect, etc. We all do this- think about an upcoming vacation. Say you’re going to Hawaii, to a hotel you’ve never been to before. You have an image in your head of the hotel, your room, the pool, maybe the lobby. Maybe the image has been influenced in part by photos on a website or in a brochure, but it’s still in your head; when you actually get there, they layout of the place will be somewhat different.
I do this all the time in ordinary business travel. I visualize the airport, the hotel, the offices of the company I’m going to visit. Closer to home I do it when I’m going to check out a new trail; I have an image of what it will look like, which stays in my head until I get there and actually see it.
Most of the time these “blank spot visualizations” are instantly swept out of mind by the actual, real-world image once I actually get to, see, and “fill in” the blank spot. But sometimes, when I finally reach a blank spot that I’ve thought about for a long time, such as the Newfoundland range or Cerro Piñones, the visualization lingers for a bit as my mind seems to try to somehow reconcile the two. I’ve mentioned before that I have frequent dreams of “wrong geography”, where I see landscapes or actual maps that are different than real world. I wonder if the source of such dreams is the countless “blank spot maps” my mind is continually creating and discarding…
In my ideal life, I’d dedicate a day a week to checking out, and filling in, blank spots. And if I ever (unlikely) managed to fill them all in, then I guess I’d move someplace else and start over again.
First Cool Thing About The Books Cliffs
First, the Book Cliffs are the longest continuous unbroken escarpment on the planet. That’s right- you can drive from Grand Junction to Helper and be alongside them the entire way. There’s no other place on Earth with a similar feature of such length and continuity. Isn’t that amazing? And yet I don’t think there’s a sign or a pull-out or anything that points that out…
Second Cool Thing About The Book Cliffs
Secondly, the Book Cliffs have a rich human history, reflected in the incredible archeological wealth of the area. The draws and side canyons of the area are practically rotten with rock and art and graffiti, dating from archaic to historic times. Nine Mile Canyon is the classic example, but Range Creek, an area which just became known to the public in the last decade, is even more amazing. (Later in the post, we’ll visit yet another example of such archeo-booty.) Even in the modern day, the Mesaverde formation is significant, in that it houses all of Utah’s currently mined coal seams.
Third Cool Thing About The Book Cliffs
And third (and as always, I have saved the coolest thing for last) the Book Cliffs are moving. No, no, no- I’m not talking about moving as in continental plates, yada, yada moving. Yes, of course they’re moving like that- everything is. But the Book Cliffs are moving faster; they are practically walking North across the land.
More specifically, they’re eroding across the land. In many posts we’ve looked at various example of geologic erosion. But what’s interesting in this landscape, where the geologic layers are more or less flat and non-convoluted, is that the primary direction of erosion is not vertical, but horizontal.
As the exposed Mesaverde cliff faces are assaulted by wind, rain and sun, they slowly crumble and fall away. Millions of years ago the Book Cliffs stood far to the South of where they are today, and millions of years in the future they’ll stand much further North.
On I-70 we turned East, away from home, and proceeded to the Thompson Springs exit, where we left the freeway and wound our way North a few miles to the base of the cliffs.
Side Note: Past the gas station Thompson Springs is a borderline ghost town- the perfect setting for an apocalypse/end-of-world/zombie movie. It knew better times in decades past as a home for coal miners and a stop for travelers, but the last half-century have dealt it a double-whammy. First, the interstate bypassed the town, which lay astride the old US6, and then passenger trains ceased stopping there in favor of Green River. Today it’s sort of creepy and fascinating- kind of like Mancos Shale.
At the mouth of Thompson Wash, a modest draw in the Book Cliffs, lies an outstanding rock art site. Over the years the petroglyphs have been heavily vandalized, but restoration efforts in the 90’s removed the worst of the offending modern graffiti. Today it’s well worth a stop. Just a few miles from the freeway, the site is festooned with art spanning possibly as far back as 5,000 – 7,000 years, including at least 4 distinct periods/styles.
Botanical Side Note: As you approach the base of the Book Cliffs, the vegetation changes, becoming better-established, taller and richer. One reason I think is that the Mancos is now covered by sandier, less-expanding/contracting soils, which are debris from the eroded Mesaverde cliffs. A second reason, specifically near the mouth of the Wash, is probably just greater moisture.
Sagebrush appears North of “town” and increases in height as you approach the cliffs. At the mouth of the Wash it forms small shrees, reaching over your head (pic above, right, Twin A for scale). Sagebrush (which I blogged about a long, long time ago) can be a bear to ID down to the species level, but whenever it gets as big as you are, chances are its Big Sagebrush, Artemisia tridentata. Fremont’s Mahonia, which we looked at a couple hundred miles to the South back in October, also reappears here. I’d never checked it out before in late Fall, but the leaves turn a beautiful lavender color (pic left).
The first is Barrier Canyon, an archaic motif we talked about down in the Grand Canyon, and which dates back as far as 4,000 or maybe even 6,000BC. Thompson Wash is one of the classic Barrier Canyon sites, just fantastic in both details and accessibility. The main Barrier Canyon panel includes 19 large anthropomorphs, up to 7 feet tall.
The second is Chihuahuan Polychrome Abstract, which dates from 700BC to 300BC. This style, which occurred across the Great Basin (further West it’s known as Great Basin Abstract) features geometric designs and patterns. One hypothesis is that the patterns represent entoptic phenomena, which are visual effects whose source originates within the eye itself. “Floaters” are an example of an entoptic phenomena.*
*“Floaters”, specifically myodesopsia, are the results of anomalies or deposits in within the vitreous humour, which is the (otherwise) clear gel filling the interior of your eyeball. The actual floaters that you see are the shadows cast by these anomalies on your retina. I see floaters occasionally, but only when looking at bright and empty clear blue sky.
Third is Fremont, the dominant culture across Utah from about 400AD – 1300AD. Fremont also features anthropomorphs, but they look more “bling-superhero” than the “creepy ghost-guys” of the earlier Barrier Canyon style. Fremont anthropomorphs are broad-shouldered, trapezoidal figures often equipped with weapons, shields and headgear. Fremont rock art has been subdivided by archeologists into six regional divisions. The Book Cliff sites, including Nine Mile Canyon, fall under the Northern San Rafael style, which features more animals and abstract patterns. This seems to be the dominant style at Thompson Wash, but one large panel here depicts anthropomorphs more in the Southern Rafael style, which runs across Southern Utah from Moab to Escalante.
The fourth style is Historic Ute*, which features such obvious post-Euro-contact elements as horses, but also sometimes incorporates elements of earlier rock art traditions. Ute panels seem to be more narrative than abstract- like the artist was telling (or recounting) a specific story. In addition to the Indian rock art, there is, as I’ve mentioned, a fair amount of Euromerican graffiti, and some of this is interesting in its own right, dating back to at least the 1880’s.
*I gave an overview of the Utes in this post.
Several thousand years, at least 4 distinct cultures/styles, mixed in with elements of neighboring styles- everything I’ve described her lies within about a 100 yard radius. And that’s the way cool thing about Thompson Wash.
A little tucked-away stopover/ retreat along the world’s longest unbroken embankment, it’s been a crossroads of cultures for thousands of years. It’s like our own little Middle East/Holy Land right here in Eastern Utah. Right off the interstate, where I’ve passed dozens and dozens of times over 2 decades, I finally stopped to check it out. Filling in blank spots pays off again and again, and I’m going to do more of it this coming year.
That was a great Thanksgiving.
Note about sources: Geologic info came from Halka Chronic’s Roadside Geology of Utah, Lehi F. Hinzte’s Utah’s Spectacular Geology*, the Inn On The Alameda website and Utahgeology.com. Info on Thompson Wash rock art came from Dennis Slifer’s Rock Art of the Utah Region. Info on “floaters” came from Wikipedia and Awesome Wife (who’s been plagued by them for some time.)
*A fabulous book with one glaring flaw: no index. Really? A geology book with no index? Are you kidding me?