Home from Back of Beyond: Images of a Harsh Country, Part Two

The photo above encompasses so much of what captivates me about the southwestern United States. A trail formed from a natural weakness in the rock providing access to an otherwise inaccessible cliff to who knows where? To be fair, hundreds of thousands of people know where the trail leads, but I like the mystery of the image. The thing is, many people DO follow this trail every year, but they may not appreciate the fact that the last time this surface was exposed to the atmosphere, it was 200 million years ago, and on the slip face of a coastal dune. Some of the irregularities highlighted by the shadows in the picture could literally be the preserved footsteps of dinosaurs, other reptiles, or amphibians.

I am slowly working on a short series of posts with my favorite images from our recently completed exploration of the Colorado Plateau and surrounding provinces. I took 1,400 photographs, so it's a bit difficult to choose between them! As we pick up the narrative, we are eight days into a fifteen day trip. As seen in an earlier post, we'd already been to the Mojave National Preserve, Zion National Park, Grand Canyon National Park, Bear's Ears National Monument, and Mesa Verde National Park. As we left Mesa Verde, we needed to find a way over the San Juan Mountains, a major range within the Rocky Mountain chain.

Because of a major wildfire in the drainage of the Animas River above Durango, we had to find another route over the mountains, so we headed instead to Lizard Head Pass (10,222 feet/3,116 meters), which divides the drainage of the Dolores and San Miguel Rivers. There was a beautiful profile of the high peaks from the summit. The brightly colored rocks above the tree line are volcanic, part of the rhyolite caldera eruptions that were taking place around 35-30 million years ago. Mineralization related to the volcanic activity resulted the emplacement of gold and silver deposits. The old mining towns like Ouray and Telluride are picturesque, but the pollution relating to the mining is a sad heritage.

Near the town of Ouray, one of the old mining camps, there is a difficult-to-see waterfall called Box Canyon Falls. The 200 foot high falls are practically hidden in a deep slot canyon, but the slopes above reveal a spectacular angular unconformity. The underlying vertical layers are more than a billion years old, but erosion planed off the rocks and in Devonian time almost 400 million years ago new sediments were draped over the older rocks. The uplift of the San Juan Mountains caused further erosion, exposing the unconformity that represents almost a billion years of missing history.

Black Canyon of the Gunnison is possibly the most bizarre canyon on the continent. It is a nearly vertical gorge that cuts through what is essentially the top of a mountain instead of having been carved through softer rocks that are exposed nearby. The Gunnison River was forced into the present channel by a series of lava flows that diverted the river from a "normal" course. Around 2-3 million years ago the landscape was uplifted, and the trapped river cut down through all the rock in its path, including the extremely hard gneiss and granite that make up the canyon walls in the park. It's not the deepest canyon in the country, but no other canyon combines the depth and steepness of Black Canyon. It is more than 2,000 feet deep in places, and in one place it is only 1,100 feet wide.

The Painted Wall (above) in Black Canyon is the highest sheer cliff in Colorado at 2,250 feet. The rocks exposed in the face of the cliff include 1.7 billion year old gneiss and schist with numerous intrusions and dikes of lighter colored granitic rock, including extremely coarse-grained pegmatite.

Late in the day we headed down one of the most spectacular roads in North America, Highway 128, which follows the Colorado River from near Interstate 70 to the outskirts of Moab, Utah. While mostly confined to a deep and narrow gorge of sandstone cliffs along the river, there is a moment when the canyon opens up and there is an awe-inspiring view of the Fisher Towers and the La Sal Mountains.

The La Sal Mountains are an anomaly in the generally horizonal landscapes of the Colorado Plateau. Between 28 and 25 million years ago, plumes of magma worked their way almost to the surface, intruding laterally between the sedimentary layers, and causing them to swell upwards like a series of blisters in the crust. The intrusions are called laccoliths. Exposed now by erosion, the igneous rocks reach elevations of almost 13,000 feet.

We arrived at our campsite in Arches National Park as the sun approached the western horizon. I don't think there is a more spectacular place in the country to roll out a sleeping bag. The view from the group camp extends for miles in every direction. There is also a beautiful arch, Skyline, visible from camp (below). The arch more than doubled in size in 1940 when a huge chunk of rock fell from the opening.

The landscapes in and around Arches and Canyonlands National Parks are almost beyond description. We spent two days in the area, and one of our stops was a rock art panel that is so delicate and fragile that I can't believe that it still exists 30 years after I first discovered it. Why? It's easily seen from the paved road leading into Canyonlands. But without signs and arrows pointing the way, people miss it. The first of the images are pictographs (below), those examples of rock art that were painted onto the sandstone. The ghostly figures and small hummingbirds are almost nightmarish in their imagery.

The other images are petroglyphs, the ones carved directly from the rocks. They depict some stylized bighorn sheep and other creatures. The panel has been somewhat damaged, possibly by natural erosion, but vandals have also done their evil work here.

Canyonlands National Park has many incredible vistas, but my favorite is the one that is framed by Mesa Arch (below). The arch is relatively small, but it frames the La Sal Mountains and pillars and cliffs of the Colorado River section of the park (the Green River forms meets the Colorado inside the park). Mesa is a popular short trail, and crowds are especially thick in the early morning when the sunrise can be photographed through the opening. You've no doubt seen an example on just about any nature-based calendar!

Pictures of Canyonlands are often mistaken for the Grand Canyon, but this section of the river includes only late Paleozoic rocks and thousands of feet of Mesozoic layers that are not seen at Grand Canyon. It is not as deep, but it is deeply colorful. It's hotter country in the summer, and there aren't many sources of water. Travel away from paved roads is more challenging than your "average" national park.

After we explored the Island in the Sky District of Canyonlands and Dead Horse Point State Park, we headed back to Arches for one of the greatest excursions on our entire trip, the hike to Delicate Arch for the sunset. The trail (a picture of which started this post) climbs 1.5 miles to an iconic overlook of the famous arch. I would love to say that the hike is an awesome desert wilderness trek where one can discover one's self in the isolation and serenity, but as author Edward Abbey feared in his 1968 book Desert Solitaire, the trail (and much of the rest of the park) has been taken over by industrial tourism. There is a large paved parking lot, and hundreds of people make the trek every evening.

Frame Arch view of Delicate Arch

The crowd at the top was rowdy, in large part because there are always selfish individuals and groups who insist on standing within the arch for selfies and group photos, spoiling the view for everyone else. I didn't have the heart to listen to the ruckus (I most certainly would have contributed, shouting at the jerks in the arch), so I headed instead to my favorite little arch in the park, Frame Arch. Frame is a small arch just above the trail only a few dozen yards from the Delicate Arch viewpoint. Most people pass it by in their race to get to more famous arch around the corner. What most of them don't realize is that Frame Arch has a great view of Delicate Arch, but also of the La Sal Mountains and Salt Wash. And I had the arch to myself for quite awhile even as hundreds of people were gathered just around the corner.

The La Sal Mountains and Salt Wash through Frame Arch

I had to think of my students though. There were a dozen of them who had hiked ahead of me, and they had to be worrying that their old overweight professor was passed out somewhere down the trail dying while they were enjoying the view. So I climbed down from the arch and back onto the trail and walked the last few yards to the overlook. I patiently waited while the jerks stood for their pictures in Delicate Arch and finally got a picture sans people as the sun settled into the horizon.

Our trip wasn't over. We had five more days and two more states to traverse. More favorite pictures soon!

Vagabonding across the 39th Parallel: A Canyon Where Cameras Stand Sideways

You walk to the edge of the precipice, and you lose all sense of proportion. The rocks at your feet drop off in vertical cliffs into the darkness nearly 2,000 feet below. The opposite rim seems close enough that you are tempted to try and throw a rock across (but it is more than a thousand feet away).  You have never seen a canyon quite like Black Canyon of the Gunnison.

It didn't take some of you very long to figure out where we were in the last vagabonding post; I was describing a place that could have been the much more familiar Grand Canyon National Park, a place with a less visited North Rim, and a heavily trafficked South Rim, but we were in Colorado instead. Black Canyon of the Gunnison National Park preserves one of the most unique canyons in the world, a canyon so deep that cameras start standing sideways in the hands of photographers leaning over the rim. The canyon just doesn't fit in the picture any other way.

The canyon seems impossibly steep. The walls are made of extremely tough metamorphic gneiss and schist, intruded by dikes and sills of equally tough granite pegmatite (an extremely coarse-grained variety of granite; many of the crystals of quartz, feldspar and mica are more than an inch across). The rocks are some of the oldest to be found anywhere in the western United States; they date to Proterozoic time, around 1.7 billion years ago.

 A canyon that in many places is deeper than it is wide. It defies belief.

The Painted Wall is the highest unbroken cliff in Colorado with a drop of more than 2,000 feet. The gneiss and schist exposures are dark, while the pegmatite dikes are lighter in color. The rocks record a complex story of continent-terrane collisions, intrusions and mountain-building episodes. The rocks on the rim preserve a relatively flat surface representing a profound amount of erosion...many vertical miles of rock are missing, having been converted into an unimaginable mix of pebbles, sand and mud distributed by rivers that long ago ceased to exist.

The very existence of the canyon is a handy mystery. It carves through what is essentially the top of a mountain ridge, and looking at maps, it looks like the river should be flowing someplace else. One has to drive a long way uphill to reach the south rim. The canyon is an example of a superimposed drainage, one whose pathway was established by external factors (lava flows from adjacent mountains) until it was trapped into flowing across a place that seems to make no sense.

I've been to Black Canyon of the Gunnison many times over the years, but always via the paved roads on the South Rim out of Montrose, Colorado. The park could never be mistaken for a place like Grand Canyon, as it lacks stores, gift shops, hotels, and hordes of tourists. But the North Rim was always mysterious to me.

I could see a single gravel road, and on rare occasions, a car traveling slowly along the edge. The rim was so close and yet incredibly remote, impossible to reach without setting aside a good portion of a day. I wondered what it was like over there, with no pavement, no tourists, just the wind and silence.

My chance to visit the North Rim of Black Canyon happened in July while we slowly made our way home while vagabonding across Colorado and Utah, roughly following the 39th parallel. We had left the Rocky Mountains behind, and when we crossed McClure Pass, we entered into the Colorado Plateau, the high uplifted region extending across the entire Four Corners region. When we paused in Paonia, an old coal mining town, I glanced at the map and realized we were only a few miles from the remote part of the park. The road was gravel, but not at all difficult to negotiate, and after an hour or so we arrived at the only developed spot, a ranger station. The ranger seemed gratified to have a couple of visitors.

We passed a small primitive campground (mostly empty), and walked out the edge of the abyss. We were alone on the trail. It was a calm day, and the canyon swallowed up any noises. We stared at the cliff faces and marveled at the vertical walls. The patterns of the rock were complex and almost hypnotic.

 I loved this place.

We finished our walk and jumped in the Subaru to traverse the rim drive for a few miles. We saw one other car. We couldn't help but stop every few feet to snap another picture. One thing I found amazing was the persistence of life. Mature trees were clinging to life on vertical ridge lines that could barely have enough surfaces to develop soils.

The shadows were getting longer, and we still had quite a few miles to go. We headed out the access road to the north, and found our way back on to the highway to Ouray. We had a nice view north to the Elk Mountains and an interesting looking volcanic neck. It was a nice visit.

The next day we would be heading into Utah...

Time Beyond Imagining: A Scrambled Landscape in Colorado

We are continuing a march towards the end our narrative on the geological history of the Colorado Plateau, one of the most unique regions on the planet. We've traversed nearly two billion years of strange events culminating in the beautiful scenery that we see today. In the last post, we were exploring a canyon that was missing a river. Today, we are looking at a river that is there, but shouldn't be.

Black Canyon of the Gunnison National Park sits in the western part of Colorado near the towns of Delta and Montrose. The park preserves a spectacular stretch of the Gunnison River where it has carved a canyon 2,000 feet deep, but which in places is only 1,300 feet across. The walls of the gorge are mostly vertical, having been cut through the very hard metamorphic and plutonic rocks of the early and middle Proterozoic. Other major rivers flow through the region, including the Colorado and Dolores. The thing is, no place on the plateau is quite like Black Canyon. It makes no sense at all.

The problem becomes apparent when one approaches the park from the south. The road travels up a long grade out of a wide open valley that looks like it ought to have a large river in it, but it doesn't. Gullies on the south rim of the canyon flow away from Black Canyon, not into it. The river flows across a major uplift, and traverses the side of a ridge instead of a seemingly natural route to the south. How can this be?

The previous post on Unaweep Canyon showed that rivers can abandon one canyon for another by way of stream piracy. Other events can divert streams as well, landslides being one example, and lava flows for another. Black Canyon falls in the latter category.

The original river flowed across a landscape composed of softer sedimentary rocks, thousands of feet above the present surface. As the landscape was eroded in the years since the end of the Laramide Orogeny, volcanoes became active in the region, forming the West Elk Mountains, and diverting the river southward. By the time the river encountered the hard metamorphic rock, the channel was permanently entrenched, and the river could only cut downwards. And cut it did, carving much of the present-day gorge within the last 1 or 2 million years. Glacial runoff vastly increased the cutting power of the river, perhaps five times the present day flow (which is controlled by upstream reservoirs).

Black Canyon is a fascinating place, in a region of full of interesting sights, including Colorado National Monument, the San Juan Mountains, and the Grand Mesa. The region is well-known for numerous dinosaur discoveries as well. Check it out!

Time Beyond Imagining: A Scrambled Landscape in Unaweep Canyon

In our last exploration of the Cenozoic story of the Colorado Plateau, we were looking at a sort of mystery canyon, where a deep gorge had been cut into very tough Proterozoic rocks, but where no river exists today. The name of this beautiful canyon is Unaweep, which in the Ute language means "Canyon with two mouths". That's another view of the canyon in the top picture. To help explain what went on here, I have included a picture of another incredible place in the same region, Black Canyon of the Gunnison National Park. I wrote about the rocks of Black Canyon last year in this post, but had little to say about the location of the canyon itself. Like Unaweep, it doesn't make a whole lot of sense at first.

Notice how similar the two canyons are in certain respects. The main gorge is cut through the hard crystalline metamorphic rocks which date back to around 1.7 billion years ago, and there are softer sedimentary rocks along the canyon rims which have eroded back into a more muted topography. And then observe the big difference: Black Canyon is 'V' shaped, and Unaweep has a flat floor giving it more of a 'U' shape. A 'U' shape should cause even a basic geology student to think "glaciers", and glacial action would make a certain amount of sense. The ice ages ended only a few thousand years ago, and glaciers could have accounted for the shape of the valley and the fact that no obvious erosional agent exists in the canyon today. The region is elevated enough, and glacial action has indeed been suggested by researchers in recent times. I am unconvinced, though, because of the general lack of glacial features beyond and above the rim of the canyon. But it is a reasonable hypothesis.

On the other hand, the similarity of the canyons cannot be dismissed. If you removed the Gunnison River, and let debris fall off the cliffs into the valley, it would start to fill in. And what if the river were dammed in some fashion? Again, debris would fill the resulting lake, forming a flat valley floor. But how can a river disappear?

When canyons erode, they don't just get deeper. They get wider as a result of mass wasting of the canyon walls, but they also get longer as a result of headward erosion. The steepest part of a canyon system is often at the headwaters of the stream, and erosion tends to eat into the slopes of the mountains in an upstream direction. If a canyon is vigorously eroding into a mountain, it may actually intercept and divert drainages that were flowing in other directions. In other words, a river can steal the water from another river, an act of stream piracy. With the addition of more water from the stolen stream, the original river may erode even more rapidly, causing extensive changes to a landscape in a short period of time.

You can probably see where this is going: what about the beheaded stream? Bereft of water, the canyon downstream of the diversion no longer has a river of any consequence and erosion ceases. Mass wasting of the canyon slopes will start to fill it in, and one is left with a mysterious gorge with no river inside.

This is almost surely what happened at Unaweep Canyon. There is still a great deal of debate about the origin of the gorge; geologists are not actually sure which river once flowed here. Was it the Gunnison, the Uncompahgre, or was it actually an ancient path of the Colorado River? It is a neat little problem, and is well worth a visit if you are ever traveling in the country between Black Canyon and Grand Junction, Colorado. Follow Highway 141 south from the village of Whitewater to Gateway.

The location of the Gunnison River as it flows through Black Canyon is another mystery altogether! More on this soon...

Time Beyond Imagining - An Intro to the Colorado Plateau

I would like to use a series of posts to illustrate the incredible story revealed in the rocks of the Colorado Plateau where I held class for the last two weeks. The Colorado River and her tributaries have laid bare a wide swath of the earth's crust, exposing more than two billion years of earth history. Few places offer so much information, exposed so vividly, within an area that can be toured over a matter of days.

The principle of superposition tells us that in a sedimentary sequence, the oldest layers will be exposed deeper within the surface, presuming that no overturning has taken place. It is when we find the base rocks upon which the deepest sedimentary layers are laid that we find the truly ancient rocks. On the Colorado Plateau, this happens in a couple of places: the Inner Gorge of the Grand Canyon, at Colorado National Monument, and especially at Black Canyon of the Gunnison National Park. If you wish to pick up a few pieces of the ancient crust, you might check some of the quarries in Unaweep Canyon south of Grand Junction, Colorado and other locales on the Uncompahgre Highlands; collecting is generally allowed on Bureau of Land Management and National Forest lands.

Black Canyon of the Gunnison is extraordinary. Over time, the deep crust in this region has been lifted and pushed upwards into mountain ranges thousands of feet high, in Proterozoic time, in late Paleozoic time, and now in Cenozoic time. Mountains rose, and mountains were eroded away. Eroded so completely that shallow seas washed over the remains of the mountains and covered them with hundreds and thousands of feet of additional sediment.

Today, the Gunnison River is misplaced, in a sense. Standing on the rim, one is struck by the way the land slopes away from the canyon walls; the deep valley more or less crosses a mountain ridge. The formation of the present-day canyon, which at 2,000 feet is often deeper than it is wide, is an entire post in itself, to be saved for another time. I want to concentrate on the ancient rocks that form the canyon walls.

The Proterozoic is what we call the time period from 2.5 billion years ago to about 545 million years. It is a vast expanse of time; all the story of complex multicelled life on planet Earth took place in the most recent 545 million years. The Proterozoic was four times as long!

The rocks exposed in the canyon walls at Black Canyon are not sedimentary; they have been changed by heat and pressure into metamorphic rock: dark biotite mica schist, gneiss, and hornfels. On the Painted Wall of Black Canyon, seen in the photo above, one can also see light colored dikes of granitic rock that melted and intruded into the older rocks about 1.4 billion years ago.

The story of these most ancient rocks on the Plateau begins with tomorrow's post!