A Place Where Water Once Was But Was No Longer, But Once Again Was (sort of) - Travels in Death Valley

Yes, I used that silly title a few weeks ago, but today it is in a very different context. We were continuing our exploration of the Death Valley region, and we were still dealing with the effects of the Bombogenesis storm that dropped so much precipitation across Southern California. We weren't able to reach Devil's Hole to see the rare pupfish because we almost got stuck in the mud. So we headed back west towards Death Valley as the storm finally seemed to be breaking up.

Highway 190 traverses a long northwestern-trending valley or trough flanked on the north by the steep and rugged Funeral Mountains. The mountains were just barely visible through the rainclouds, but we could make out thick gray sedimentary layers tilted to a high angle. Taken all together, the layers are very thick, approaching 20,000 feet, around four miles. There is quite a story in those rocks.

One of the challenges of taking new students into outdoor geological environments is getting them to recognize that the landscape that exists today is far different than those that came before. Nothing accomplishes that quite so well as releasing them onto the floor of an incredibly dry desert valley, and letting them discover that the rocks underfoot were chock-full of fossils that originated on the bottom of a shallow tropical sea. The rocks layers that make up the Funeral Mountains once lay offshore of the North American continent. California simply didn't exist 300-400 million years ago. There was only ocean.

One could argue that this was an exceedingly boring time as far as geological activity was concerned. For 200 or 300 million years there was quiet deposition of layers of lime-rich mud and not much else. It maybe wasn't exciting at the time, but to a paleontologist this is intellectual treasure beyond compare. It's rare around the planet to find places where deposition took place for hundreds of millions of years without interruption, and equally rare for such places to preserve the myriads of life forms that lived in these shallow seas.

The Grand Canyon is a justly famous and spectacular monument to the forces of geology, but the Paleozoic layers there are only 4,000 feet thick, and entire periods (the Ordovician and Silurian) are missing. The fossil record is incomplete. Death Valley National Park on the other hand has layers dating from every period within the Paleozoic era, as well as Cenozoic layers that are entirely missing from the Grand Canyon. It has one of the greatest fossil records to be found anywhere in the national park system. That what we were out to find that afternoon: fossils!

It shouldn't have be said, but we were outside of the boundaries of the national park. Collecting within the park boundaries is quite logically not allowed. We do enough damage to the resource as it is without hauling it off, to be lost to science.

A huge number of fossils lay scattered across the desert floor. The predominant fossils were the bits and pieces of crinoid stems (sea lilies) that once covered the floor of the sea like waving fields of wheat. Even though the crinoids were anchored by roots and had stems, they were most certainly animals, specifically echinoderms. This is the animal phylum that includes starfish, sand dollars, sea biscuits, and urchins. All of these animals are related by a kind of five-fold symmetry: the five legs of the starfish, the five feeding grooves on the surface of the sand dollars. The symmetry can be seen in the "star" shape in the middle of the stem fragment (above).

Other finds of the day included corals and brachiopods. For the students, it was the beginning of an understanding that the desert beneath their feet was truly a place where water once was, but was no longer. And with the continuing rain, it was a place where water was once again, however termporary.

Death Valley is Really Second Generation Death Valley: A Look at Death Valley Version 1.0

Death Valley is a stunning example of a fault graben, a large area of crust that subsided because of extensional forces that produced widespread "normal" faulting (where the fault plane slopes towards the basin). The valley has relief of more than two miles, from the summit of Telescope Peak at 11,043 feet (6,168 meters) to Badwater Basin at minus 282 feet (-86 meters). Perhaps more extraordinary is the fact that the valley has filled with eroded sediments to a depth of as much as 9,000 feet. Remove the sediment and Death Valley would be nearly four miles deep!

One might imagine what it would look like if the sediments of Death Valley were somehow lifted up and dissected by erosion. What would one see? There would no doubt be layers of salt and gypsum, silt and clay, and conglomerate and breccia from the alluvial fans that line the margins of the valley. Volcanoes are found along the margins of the Death Valley today. Perhaps one could expect to see colorful exposures of lava and tuff in the deeply buried valley sediments.

What's fascinating about Death Valley is that we don't have to imagine what the valley fill would look like. It turns out that the graben that formed the valley is not the first to have existed in this area. It formed around two or three million years ago, but extensional forces have been stretching this region for something like 15-16 million years. Other grabens developed, filled with thousands of feet of sediment, and were lifted by faulting so that erosion revealed the underlying rock and sediment. One of these more ancient basins is revealed at Zabriskie Point, one of the most visited and dramatic of Death Valley's tourist destinations. The rock is called the Furnace Creek formation.

The rocks of Death Valley-Version 1.0, as seen in the Furnace Creek formation consist of fine-grained silt and clay interspersed with evaporate minerals like salt, gypsum, and most importantly for the miners of Death Valley, borates. There are layers of conglomerate and breccia from ancient alluvial fans, and colorful tuff and lava flows from associated volcanic activity. In the dry environment of Death Valley, the rocks have eroded into the intricate badlands that made Zabriskie Point a must-see part of any trip to the park.

The badlands are practically devoid of any kind of plant life. The barrenness results from the inability of stable soils to develop on the steep slopes. Any soils are quickly washed away during infrequent but violent cloudbursts.

The layers exposed in the Furnace Creek formation provide information about ancient environments that once existed in the Death Valley region, but also feed the imagination about the rocks hidden deep within today's fault graben, Death Valley-Version 2.0.

This has been another in an off and on series about our February visit to Death Valley. In the next installment, we'll be leaving Death Valley for other sights in the region, a detour made necessary by October flash floods that took out some of the park's roads. We'll be visiting a unique biological island in the desert...

Like a Gigantic Babushka Doll, One Death Valley inside Another Death Valley

Death Valley is a deep structural trough called a graben, formed by faults that stretched and broke the continental crust, mostly within the last two or three million years. It is just one of dozens that are present across the deserts of eastern California, all of Nevada, and much of western Utah, a region known as the Basin and Range Province.  But as grabens go, Death Valley stands out. It is almost twice as deep as the Grand Canyon, as the Panamint Mountains slope 11,000 feet down to the valley floor that sits below sea level. It's also one of the flattest places you can stand on planet Earth.

But the valley we see is only part of the story. As is always true of any mountain, if it sticks up into the atmosphere, it will be eroded. It doesn't matter how dry the climate is, erosion happens anyway, albeit at a slower pace perhaps. Sediments have been filling in these valleys. As high as the mountains are, another two miles are hidden by the sediments that fill the valley floor.

I imagine some people wonder what's under all that salt. Wouldn't it be cool to see some of the history revealed in those sediments?

All I can say is that Death Valley is one awesome piece of geology. Whatever you might seek about geological processes or history, there is probably a world-class example of it at the park. So you want to see what Death Valley would look like from the inside-out? We've got you covered! There have actually been two Death Valleys, and one of them has been turned on end for us to explore.

About 5 or 6 million years ago, extensional forces were stretching the crust in the Death Valley region, but from a different direction. A major fault graben opened up in a northwest/southeast direction, mountains rose on either side, and erosion began to fill in the trough. Eventually the sediments accumulated to a depth of a mile. Sometimes a permanent lake filled much of the valley, resulting in the deposition of layers of fine silt and clay. At other times, the lake dried up, leaving behind halite (table salt), gypsum, and borate minerals. Alluvial fans, composed of gravel and conglomerate, sometimes spread across the valley floor. There were occasional volcanic eruptions as well.

The sequence of sediments and lava flows is called the Furnace Creek formation. Few fossils are found in the rock, but trackways of horses, camels, mastodons, large cat and wolf ancestors, and birds have been found. These fossils point to a diverse ecosystem that was not quite as dry as that of today's Death Valley, but is certainly analogous to the Death Valley that existed during the ice ages.

Then things changed.

The regional stress pattern shifted and new faults formed, the faults that produced the present-day Death Valley graben. The deeply buried rocks of the Furnace Creek formation were pushed upwards, folded and tilted, and ultimately exposed to erosion. In the harsh desert climate soils do not develop on the fine silts, so the barren slopes give way to deep gullies and furrows called badlands topography.

And so today, we can have a look at Death Valley from the inside out.

Most tourists who visit Death Valley observe the Furnace Creek formation at the spectacular view from Zabriskie Point or from the resort area at Furnace Creek. We usually do a field exercise at Zabriskie, but the entire area was closed this year for renovation. So we headed up Twenty-Mule Team Canyon for a look at the colorful outcrops. The gravel road winds for several beautiful miles through the badlands.

The Furnace Creek formation was the greatest source of riches in the Death Valley region. Forget gold or silver or copper. The borate minerals, formed from geothermal hot springs in the graben of the Furnace Creek formation, were mined for their use as soaps and detergents, a flux in glass-making, in cosmetics, and numerous other applications. For a number of years in the late 1800s the only economic sources of the borate minerals in the world were in Turkey and Death Valley. They were still being mined in Death Valley as recently as 2005.

The Furnace Creek formation is a spectacular part of the scenery of Death Valley National Park, but the colorful exposures provide a window into the geologic history of the western United States as well. Peel away the surface layers and we find pieces of the past when conditions were far different. Peel back that layer, and we find another story.The Furnace Creek formation is but one of dozens of geologic strata exposing more than a billion years of changing environmental conditions. The park is one giant Babushka doll of geologic history.

Out of the Valley of Death: Mountains and Mountains of Animals

So many colors in a desert environment! It was the second morning of our trip into the Valley of Death, or Death Valley National Park as others call it. On the previous day we had made our way across the southern end of the Sierra Nevada after searching for shark tooth fossils in the dusty hills near Bakersfield. We then crossed the Garlock fault at Red Rock Canyon State Park and drove north into the Owens Valley and looked at the dry water course at Fossil Falls. Late in the day we had forced passage over two mountain ranges, the Darwin Plateau at the south end of Inyo Mountains, and the Panamint Mountains. Of course, passing over mountain ranges in the modern day is a great deal less difficult than it used to be.

We set up camp in the dark, and so had no idea the scene that would greet us in the morning light. It was glorious. There was movement in the camp as the students started waking up and looking around. It was going to be an interesting day.

There was a storm brewing out in the Pacific Ocean, and I was sure we were going to catch a corner of it, but storms come to die in Death Valley just as surely as the dreams of avarice in the eyes of miners wither in the face of the desert heat. All we could see of the weather disturbance were the high clouds drifting above.

Few of the original settlers who were trapped in Death Valley and gave it the name actually died. On the other hand, the mountains that surround the valley are full of death, in a way. For several hundred million years the region that is today Death Valley was a passive continental margin on the edge of the (much smaller) North American continent. Rivers carried some sediment into deltas that connected to the shelf, but mostly in the tropical conditions limestone formed, more often than not as the result of organic activity. As organisms died, their shells became incorporated into the limestone layers that dominate mountain ranges surrounding Death Valley. The formations ultimately reached a thickness of at least 20,000 feet. There are mountains of animals!

Erosion has ripped away the rocks and deposited them in widespread alluvial fans, and the remains of the ancient creatures can be viewed in the rocky detritus. The students were interested in searching for them. The urge to collect can be powerful, and that's illegal in a national park, so we headed east towards the park boundary on the road to the Amargosa Valley and Death Valley Junction. When we stopped, the students scattered across the desert, not finding much at first, but soon there were cries of discovery. Horn corals (below), crinoid or blastoid columns (the next picture after), brachiopods, bryozoans, gastropods, and even an occasional cephalopod.

 Some of the samples were quite showy!

Occasionally I looked up towards the forbidding peaks of the Funeral Mountains and contemplated how many creatures lived, struggled and died to make up the many thousands of feet of carbonate rock in the slopes above. Untold trillions...

From Little Treasures Come Big Stories: Travels Through Death Valley National Park

Photo by Mrs. Geotripper

I returned from Death Valley to a load of work back on campus, but over the next few days I'll be posting on some of our adventures. On Saturday morning, we awoke to sunrise on the Mesquite Dunes east of Stovepipe Wells. We grabbed our packs and notebooks and hit the road. We had a lot of ground to cover.

Oddly enough, for having spent two days getting to Death Valley National Park, one of our first stops was outside of Death Valley National Park. This was for the simple reason that we were looking to understand the nature of the rocks that make up the mountain ranges surrounding Death Valley. Because we didn't have enough time to climb most of the mountains, we would need to see what had rolled out of the mountains during the many flash floods and mudflows that had scoured their flanks over the countless centuries. I have honest students, but their conscience would have had a tough time dealing with all the little treasures they were about to find. So we made sure we were outside the park boundaries when we let them out onto the alluvial fans coming down from the Funeral Mountains. For many of my students it was their first experience in finding a fossil.

Fossil crinoid stems. These are rare in oceans today (they are known as sea lilies), but during the Paleozoic era, they covered the sea floor like fields of wheat, and entire rock layers are composed of their fragments.

To most normal people, 300-400 million years of nearly continuous mud deposition is perhaps not the most exciting process to consider. But if that 300-400 million years covers the latest Proterozoic eon and the all of the Paleozoic era, such activity is irresistible to a paleontologist. A rock sequence that covers that time period contains the evidence of the rise of multicelled life on Earth, as well as the first appearance of all of the extant phyla known (plus a few extinct ones). A phylum, as a biologist will tell you, is one of the broader divisions into which all life can be organized. One phyla, the chordates, contains all the familiar animals with a notochord or backbone (fish, amphibians, reptiles, birds, and mammals). There are dozens of others, including the arthropods (bugs and crustaceans) and the molluscs (snails, clams and squids) which make up most of the species known today. A more or less continuous record of deposition makes it possible to detect patterns and trends in the evolution of life on the planet through time.

Grand Canyon National Park has a similar range of rocks exposed in the depths of the gorge, but huge pieces of the story are missing because of episodes of erosion. Where the Grand Canyon has about 4,000 feet of Paleozoic sediments, Death Valley has more like 20,000 feet! How can 20,000 feet of sediment fit into a mountain range that rises no more than 5,000-6,000 feet above Death Valley and other grabens in the region? If you look at the photo of the Funeral Mountains below, the answer is apparent: the sediments in the mountain range have been tilted. To walk through 400 million years of Earth history, we need only to walk a few miles along the base of the mountains.

How is it that sediments could accumulate for such a long time in such stable conditions? Most parts of the crust of the Earth are wracked by extreme tectonic activity like volcanism, folding, and faulting. The Paleozoic rocks of Death Valley accumulated in one of the most geologically "gentle" environments on the planet: a passive continental margin. A billion or so years ago, most of the world's continents were combined in a supercontinent we now call Rodinia. The continent began to break up at the end of the Proterozoic, which is a process that involves severe faulting and rifting, along with vigorous volcanic activity, but as the continents moved further and further apart, the processes became less active and finally stopped. The edges of the continents became a site of more or less continuous shallow marine deposition, and as more sediments were laid down, the crust slowly sank beneath the weight, allowing even more sediments to accumulate.

So, from a bit of wandering across a stony desert surface picking up random fossils, a story is told of massive supercontinents breaking apart and forming huge wedges of sedimentary rock that tell the story of 400 million years of evolution of life on planet Earth. In short, this is why I love teaching geology.

Death Valley Days: The Fourth Day - The Long Road Home

Day dawns on the Cottonwood Mountains west of Stovepipe Wells. We've got about 400 miles to reach home, but we weren't going to let that stop us from doing a few last minute stops at Death Valley National Park. We've spent three days exploring the region (here, here and here), successfully avoiding the worst of California's storms this last weekend, and seeing some wonderful geology.

Tucki Mountain is an immense edifice rising 8,000 above our camp at Stovepipe Wells at sea level. The shape of the mountain is reminiscent of a turtleback fault, and it may in fact be an incompletely exposed metamorphic core complex (I would love to hear from the structural geologists about it). Mosaic Canyon is a deep gorge on the north flank that narrows down to a twisting labyrinth in its lower reaches. It is a main tourist stop, but most visitors never notice the spectacularly exposed structural features.

Just a short distance up the canyon from the parking lot is one of the best exposed examples of a normal fault I can imagine. Laura is resting her back on the headwall and sitting, more or less, on the footwall. The different colored layers show that the headwall dropped relative to the footwall, indicating extensional stress.

A little further up the canyon, the so-called 'mosaics' appear, chunks and pieces of canyon alluvium that were lithified, glued to the canyon walls, and exposed by continued downward erosion of the canyon. The photo above would serve as a perfect example of the appearance of an angular unconformity (a buried erosion surface with tilted rocks beneath and horizontal layers above), although the specific relationships here stretch the definition a little bit.

Paul was describing a large recumbent fold in the upper part of the narrows. These rocks have undergone an astounding amount of deformation, having been twisted into tight folds multiple times.

We made our way down the canyon for one last restroom break and chance for curios and t-shirts, and starting winding our way up into the Panamint Mountains for a last look at the valley. The road down the Mosaic Canyon fan provided a marvelous view of the Death Valley Dunes (Mesquite Dunes). Contrary to many people's stereotypes about deserts, dunes are a relatively rare part of the landscape in a place like Death Valley. Powerful winds blow the sands off the alluvial fans and down the long valleys until some flank of a mountain range interrupts the flow of the wind. The sand is deposited and shifts back and forth in the wind eddies. The highest of the dunes reach 150 feet or so. They are especially fascinating at night and in the twilight hours. In the morning the surfaces are covered by trackways of insects and animals. Most people don't realize they have seen the dunes; they were a stand-in for the Star Wars planet of Tantooine (the Dante's View panorama of Death Valley was used for the setting of Mos Eisley).
The interruption of the fan in the far distance is the trace of the Furnace Creek fault, a strike-slip fault that follows the base of the Funeral Mountains on the skyline. Death Valley hasn't been historically active as far as earthquakes go, but there are many signs that the faults are quite active.
We drove up the gravel road to Aguereberry Point. The gentle rolling landscape gave little indication of the jagged cliffs just over the ridgetop. These hills give some indication of the topography of the region prior to the formation of the deep fault grabens of Death Valley and Panamint Valley. They were preserved as the mountains rose and valley collapsed, but in the fullness of geologic time, the hills will be breached by headward erosion and will disappear.

We topped the ridge at 6,000 feet and arrived at Aguereberry Point. Being at the end of a gravel road, it receives far fewer visitors than Dante's View, but it is no less spectacular. One stands beneath the flank of 11,049 foot Telescope Peak, and has a sweeping 270 degree view of Death Valley, the Panamint Mountains, the Inyo Mountains, and the Sierra Nevada in the far distance. At our feet was the massive alluvial fan of Furnace Creek, the location of many of the park's tourist facilities.

The salt flats of Badwater and the Black Mountains fill the view to the southeast. In the foreground are tilted Paleozoic sediments, carbonates and sandstones that were deposited in shallow seas, but ultimately accumulated to depths of many thousands of feet. We were standing on quartzite that was once a beach in Cambrian time 500 million years ago. We could see the burrows made by countless worms in the tropical climate.

Finally the last geology stop was complete, and we hit the long road home, via Trona, Ridgecrest, Bakersfield and Fresno. It was a good trip! I hope you've enjoyed the virtual tour.