Out in America's Never Never: Exploring the Grand Canyon...in Las Vegas?

Photo by Mrs. Geotripper

I'm sure no one needs to be told that visiting Las Vegas is a surreal experience. I can't even begin to imagine the army of psychologists who through the years have advised casino owners on the best ways to separate tourists from their money. I've been appalled at the... well, I can't come up with any term better than excess. Las Vegas serves as a fine definition of the word.

I wonder what the point is of seeing the canals of Venice, a circus, New York, and the Egyptian pyramids when one could presumably see the real thing? One of my stranger experiences was the time I left the South Rim of Grand Canyon and arrived at a casino decorated as...the Grand Canyon. Complete with animatronic deer and raccoons. And plastic pine trees.

And yet, strangely enough, one can explore the Grand Canyon in Las Vegas, at least in one sense, and more easily than one can in the National Park. Our journey through the American Never Never took us from the Mojave National Preserve to Sin City because of the access it provides to the Proterozoic and Early Paleozoic rocks that in the park are only found deep in the canyon at the end of a hugely strenuous hike.

Photo by Mrs. Geotripper

Frenchman Mountain rises east of the city, at the boundary between the city limits and the Lake Mead National Recreation Area. The mountain mostly falls under the jurisdiction of the Bureau of Land Management, which for decades let the land languish as a shooting gallery and trash dump. Geologists have known for years (especially since the 1960s publication of John Shelton's Geology Illustrated) that the rocks exposed on the flanks of the mountain were the same as the formations found in the deepest part of the Grand Canyon. One can easily lay one's hand across 1.2 billion years of geologic history at the exposure of the Great Unconformity (it's at my feet in the picture above, sloping up to the right). One can see the cross-bedded sandstones of the Cambrian Tapeats Formation, the remains of a shallow sea that transgressed across the western margin of the North American continent. And in the small canyon above these exposures, one can pick out trails, burrows and the discarded carapaces of some of the earliest complex life forms to be found on our planet, from the Bright Angel Shale.

It is an interesting story just explaining how rocks of the Grand Canyon came to be exposed here in the Las Vegas Valley. In short, the rocks were transported 50 miles westward by extreme extensional faulting in Miocene time, around 23 to 6 million years ago. A major detachment fault system is presumed to underly the region (below).

Source: Stephen Rowland, UNLV

It's an important and significant geologic locality, one that would be worthy of an interpretive sign and trail. In the 1990s, students and volunteers associated with the University of Nevada, Las Vegas put in a tremendous amount of work to construct such a site. It was very nicely done, with a brick walkway, sturdy interpretive signs, and a short nature trail.

This was the roadside interpretive sign that explained the value of the site (source: Stephen Rowland, UNLV)

But no good deed goes unpunished. The site was in place by 2001, and within a few short years it was completely obliterated by vandals. It sickens me beyond words that such people exist who feel compelled to destroy the good works of others.

Still, it is a great place to visit and learn a bit of geology. The signs are gone, but so is most of the trash and garbage, and a walk up the hill provides a stunning view of the most unlikely city in existence. Download the information from the UNLV website at http://geoscience.unlv.edu/pub/rowland/Virtual/virtualfm.html and you won't need the signs anyway.

Next time you find yourself in the city of casinos, here is something you can do that doesn't remove money from your pocket! Check it out...it's at the end of Lake Mead Boulevard in the northeastern part of the city on the way to Lake Mead.

What's Missing From This Picture? Only a billion years or so...

Geology is good for perspective. The bookends of this particular day: the very very long hour spent trying to restart a dead car in a remote canyon, and a billion years in one hand. I'm on the road researching a field seminar for the AAPG in Arizona and Nevada, and I saw some incredible things.

1.7 billion years ago, fragments of continental crust were colliding to form the core of a new North American continent. Those mountains climbed to the sky, rivaling the Himalaya or the Andes in their grandeur. The time was so ancient that not a bit of life existed on the mountain flanks. The only lifeforms at all were single-celled organisms in the oceans.

The forces pushing the mountains upwards ended, and the ice and rain tore away the flanks. The gigantic peaks eroded to hills, and in hundreds of millions of years, the hills eroded to nearly flat plains. They were gone, but the rocks that formed the roots of those mountains remained. Around 530 million years ago, the continent had begun to break up, and the edges subsided slowly while a shallow sea advanced. The beach sands swirled back and forth across the roots of the ancient mountains.

An unconformity is a buried erosional surface. Sometimes the time missing might be a few hundred thousand or a few million years. The unconformity in the Grand Canyon is profound, representing a gap of a one thousand million years. Get to the right place, and you can place your hand across 1,000,000,000 revolutions around the sun: nearly a quarter of the age of the Earth.

The problem with the Great Unconformity, as the early geologists called it, is that it is mainly exposed in the bottom of the Grand Canyon. There are only a few ways to see it and touch it: you can float down the Colorado River in a raft, or you can walk down the long difficult trails from the rim of the canyon. Or, as it turns out, you can drive.

I left Las Vegas this morning and traveled up Lake Mead Boulevard. The growth of the town has slowed with the depression, but over the last twenty years I've watched the urbanization of the valley wash up the slopes of Frenchman Mountain on the eastern edge of town like a tsunami. Fortunately, the wave stopped at the boundary of the city limits and the federal lands around Lake Mead. It turns out that the rocks making up the Great Unconformity are exposed no more than a mile from the residential neighborhoods of Sin City. The sand layers of the Tapeats Sandstone cover the weathered granite and schist of the 1.7 billion year old basement complex.

The geologists at the University of Nevada, Las Vegas knew of the treasure in their backyard. Years ago they set up a trail and some very nice interpretive exhibits. I regret to say that vandals and garbage dumpers destroyed the exhibits in a short time, but you can still see the rocks.

If the exposure lacks anything, it is grandeur. The oldest rocks of the Grand Canyon are at the bottom of one of the deepest and longest gorges in the world, and there is much to be said for seeing the rocks in their full perspective, underneath a mile of subsequent sedimentary layers. When time or health is short, hiking or rafting is not feasible. But I was on a mission today, to see the only place in all of the Grand Canyon where one can drive to the Great Unconformity. It is well-known to rafters as it is the take-out point for the river voyagers. It's called Diamond Creek, and Peach Springs Canyon. The road starts at the administrative headquarters of the Hualapai Nation in Peach Springs, and winds 19 miles and 3,500 feet down to the Colorado.

Anyone who has seen the Grand Canyon, either in pictures or in person, has to wonder how any road could intrude into such rugged terrain. There are so many cliff-forming layers that a road seems next to impossible (which it is, given that only one exists). But Grand Canyon is also crossed by faults and folds, and the disruption of the cliff-forming layers is what makes roads and trails possible. The road starts innocently enough, dipping into rolling terrain composed of Mio-Pliocene sediments that have huge significance in understanding how the Grand Canyon was carved. We actually follow canyons that originated at the end of the age of the dinosaurs (the Cretaceous Period) and were subsequently filled, and then exhumed in the last hiccup of geological time.

Heading deeper into the canyon, we see some evidence of deformation; in the picture below, we can see a gentle monocline crossing the picture where the layers step down in elevation without splitting. A major fault zone, the Hurricane fault, crosses the canyon in front of the fold. The road turns and follows the fault zone.

The gorge becomes deeper and deeper, and we pass into older and older layers. The Mississippian Redwall limestone forms the highest cliffs, and the lower cliffs are dominated by the Devonian Temple Butte limestone and Cambrian Muav limestone. The gentler slopes cover exposures of the Cambrian Bright Angel shale. The rocks on the left side of the canyon sit around a thousand feet lower than the rocks on the right due to displacement along the Hurricane fault.

The cliffs grow higher and higher, and we finally reach the base of the Paleozoic rocks with exposures of the Tapeats sandstone, the same layer seen at Frenchman Mountain in Las Vegas. The Tapeats can be seen in the first picture of this post, forming the prominent layers at the lower left. The orange-brown rocks at the base of the cliff are the 1.7 billion year old granite and schist.

It would take only a moment's walk to lay one's hand on the unconformity, but we also wanted to see the Colorado River. We were nearly 16 miles into the canyon, with only three to go. We got into the car, turned the key....and nothing. Not a click, not a warning light, nothing. 16 miles into the depths of the Earth, and we had a dead car.

So we had the longest hour I've ever felt (aside from the births of my children), trying anything and everything to get the car going again. A construction crew stopped by, five guys in one truck, and we did the engine worship thing where all six of us stood around the open hood and jiggled connections. A river runner came up the road with his boat trailer. He had room, so Mrs. Geotripper jumped in to go arrange for a tow truck. River runners like this guy drive this road all the time, so the Missus had a regular Mr. Toad's Wild Ride up the bumpy road. Meanwhile, I stayed with the car, pretty much preparing to camp out for the night. The ranger for the Hualapai tribe showed up, and we did some more jiggling of engine connections, and he helped me get the transmission unstuck, but we still weren't getting anything when I turned the key. In final desperation, we tried the obvious, and pulled out the jumper cables. They worked.

I zoomed up the road, picked up Mrs. Geotripper, and sped on to Williams without turning the car off once. Thus, our unexpected night in a motel, and a delay, looking for a saturday mechanic before we head on to Grand Canyon tomorrow. And internet access! We'll see what surprises tomorrow holds for us.

By the way, the ocotillos were blooming in the lower canyon...enjoy!

NOTE: Tourism is almost the sole source of income for the Hualapai tribe. You need to pay an exploration fee of $25/person at the Hualapai Motel in Peach Springs. Looking at the town of Peach Springs, I was glad to give them some support.