Friday, March 31, 2017

Rock and Light, the Primal Elements of Death Valley

When one has been under gloomy overcast conditions punctuated by periods of rain for days, the novelty can run short, even in a place where rain is scarce. We had been on the road for three days and in that time we saw no sunshine, and in fact had lived through a night of record rainfall and localized flooding. What made the mood worse was that the weather forecasts had us expecting sunshine on the third day and we got rain instead.
The students were just great actually, showing all kinds of patience. They were in Death Valley after all, and they weren't in a classroom. At least not the kind with four walls. Just the same, I was pining for just a bit of sunlight, and the evening was coming quickly. We had just finished an exercise at Gower Gulch at the north end of the Black Mountains and we walking back to the vehicles when a sliver of sky opened up. The sun blazed forth in all its glory.
There are two sure things in places like Death Valley, rock and light. Deserts have dust storms at times, of course, but much of the time the air is free of pollution and humidity. The sun shines with an intensity not usually experienced in urban settings (my students traditionally come home with winter sunburns despite our warnings to use sunscreen).

And the rock...Death Valley has perhaps the greatest variety of rock types to be found in any national park. They range in age from 1.7 billion to practically yesterday. They include all of the types, plutonic, volcanic, sedimentary, and metamorphic. The rocks occur in nearly all the colors of the rainbow, sometimes in a single outcrop (google Death Valley's Artist Palette if you want to see what I mean). And in most parts of the park there is no vegetation or soil to obscure their complicated structures and relationships.
It's hard to imagine a more dramatic moment for the two elements to intersect. The sun was low in the sky, the rocks were wet from the recent rain storm, so the colors were intensified and the rocks seemed to glow with an inner light.

The rocks we were looking at were part of the Mio-Pliocene sediments and ash/lava flows of the Furnace Creek, Funeral, and Artist Drive formations. They accumulated in a fault basin not totally unlike the present-day Death Valley graben. There were ephemeral lakes, alluvial fans, floodplains, and volcanoes. The plains probably supported a rich fauna of camels, horses, mastodons, birds and predatory cats, who left their tracks in similar-aged rocks elsewhere in the park.
It was a dramatic moment, but as with so many such moments, it was fleeting. The clouds closed in again, and we thought the show was over, except that a few moments later while we drove the highway north of Furnace Creek, the skies opened up one more time to reveal a brilliant rainbow (see the opening if you somehow missed it!). The moment felt perfect.

Addendum: Since we are talking the incredible fossil record of Death Valley, there is news this week of some horrible human beings who have stolen some of the precious fossil trackways I mentioned. I can only hope that the pictures of the probable thieves will lead to arrests and convictions. More information can be found here:

Stepping From a Valley Floor into a Mountain Range: Travels in Death Valley

To me, one of the most stunning things about exploring Death Valley is the abruptness of the landscape. There are no gentle transitions. You are either on the valley floor, or you are on a mountain. There is no in-between. I'm hard put to think of another place in the world where you can stand on a valley floor and place your hand on a mountain slope. It's just usually not the way of things.
But Death Valley is like that. The main valley is more than a hundred miles long, and 10 or 15 miles across. It's a place of wide open vistas that extend for miles. But if you approach a mountain range like the Black Mountains between Badwater and Furnace Creek, you walk up the gentle slope of an alluvial fan, and then you are stopped by the mountain. Because of the active fault scarp, it rises like a wall straight up out of the ground.
We had come down onto the floor of Death Valley after looking at the diversion of Furnace Creek into Gower Gulch, hoping to get some insight into the effects of flooding a small canyon with the debris and mudflows from a drainage area of 170 square miles. It was pretty awe-inspiring. In the 70 years since the diversion, Gower Gulch had scoured its channel through the Black Mountains, and eroded a deep channel into the surface of the Gower Gulch fan. There's a 25 foot high dry waterfall at the entrance to the canyon, but a trail clings to a narrow terrace of the old alluvial fan to the left (above). It's not hard to explore the narrow canyon above.
There was still a thin stream of water flowing through the canyon, a small remnant of the flash flood that had thundered through the canyon the previous night (Death Valley had just experienced a night of record rainfall for the date, 0.62 inches; of course we were camped out in the open). The debris had covered the highway just downstream.
It's a steep and rugged canyon, one of many that begs exploration by curious people. Treasures are to be found in these canyons...old mines, colorful rock exposures, fossils, and elusive life: Bighorn Sheep maybe, or a Kit Fox. Who knows?
In the end, it's all about the landscape itself. Naked rock exposures and faults. Alluvial gravels. Stepping from a valley floor into a mountain range in one step. There's no place in the world like this...

Sunday, March 26, 2017

Travels in Death Valley: the Strange Story Told By a "Rock"...

A beautiful collection of colorful rocks lie scattered across the surface of an alluvial fan in Death Valley National Park a few miles south of Furnace Creek. There is a piece of vesicular (full of holes) basalt on the lower right, next to a piece of gray limestone. One might be just 10 million years old, while the other may be 300 million, containing the remains of long dead and extinct organisms. At the top left, a piece of orange-brown sandstone, possibly deposited on an ancient ocean shoreline, or maybe a lakeshore in a long-ago desert, maybe even a sand dune. Perhaps a piece of granite is in there somewhere, a rock that cooled four or five miles deep in the crust. What a long journey it had before it was exposed by erosion and carried down the desert wash! And then there is...wait...what is that at center left? That's no conglomerate! Well it sort of is, but isn't natural is it? That's a piece of pavement. What's going on here?
It's not a story that appears on National Park Service interpretive signs, and in fact I think the park service would rather that people not explore the particular canyon at all. It's sort of unstable, as in vertical walls made of loose and cracked chunks of claystone. And like the piece of asphalt pavement on the alluvial fan surface, it's not natural either. This canyon didn't exist 75 years ago.

Gower Gulch used to be a minor drainage in the Furnace Creek Formation badlands near Zabriskie Point which debouched onto the floor of Death Valley, forming a small alluvial fan. Badwater Road crossed the fan, which consisted of mostly fine-grained materials like silt and clay.

The problem is that nearby Furnace Creek drained a much larger region than Gower Gulch (170 square miles versus 2 square miles), and was prone to violent flashfloods and mudflows that damaged facilities at the Furnace Creek Resort about five miles downstream. Around 1941 someone thought to blast through the low ridge that separated Furnace Creek and Gower Gulch, forcing the entire drainage to flow through the badlands and onto the Gower Gulch fan downstream. The diversion caused profound changes upstream and downstream.

At the diversion point (above), the flash floods cut through the soft siltstone and shale like a hot knife through butter, cutting 40 feet or more in seven decades. The floods carry a heavy load of coarse-grained debris and gravel that acts as an abrasive on the channel floor. The canyon changes year to year as each flashflood causes slopes to be undercut, causing rockfalls and slope failures.
It's upstream where serious damage to the road occurs. The diversion caused a sudden steepening of the Furnace Creek channel, and the faster moving floods have eroded the channel in an upstream direction, a process called headward erosion. The deepening of the channel is apparent as far as two miles upstream, and in numerous places it has encroached onto Highway 190, washing away some of the pavement, and incorporating the fragments into the alluvial fan deposits downstream (as in the first picture above).
Downstream, the road damage occurs in a different way. The alluvial fan used to receive fine-grained silt and clay in relatively minor floods that did little damage to Badwater Road. Now the flashfloods are on steroids, so to speak, with more water, more debris, and far more speed. Badwater Road is regularly overwhelmed, as it was on the day we visited, with mudflow deposits. Boulders can sometimes be sizable. For example, check out the two fragments on the fan in the picture below. How big do you think they are?
Here's your answer: pretty big.

Death Valley is a monument to geologic changes over billions of years, but it is also a dynamic environment where geologic change happens on a daily and yearly basis as well. We saw plenty of evidence during our February trip.

Wednesday, March 22, 2017

Two Death Valleys in One: Travels in Death Valley Version 1.0

It's certainly not the first time I've talked about Death Valley, Version 1.0 (see this post, for instance), but it's also a story of unending fascination. The deep and very long fault graben that forms the main axis of Death Valley National Park is only the latest in a series of fault valleys that have formed here over millions of years. One of the most popular stops in the park, Zabriskie Point, reveals the uplifted remains of a desert graben that existed several million years before the present valley formed.
The Death Valley region prior to about 15 million years ago was part of a vast high altitude plain that sloped west towards the Pacific Ocean, several hundred miles away. This feature, sometimes called the Nevadaplano, predated the latest uplift of the Sierra Nevada, so rivers flowed across the otherwise gentle terrain of rolling hills towards the sea. Much of this surface had been covered by eruptions of rhyolite ash that spread from vast calderas off to the east. But the tectonic arrangement of the American West was transforming (literally; the newly forming San Andreas fault was becoming a transform boundary) and big changes were coming.
Because of intense extension, the crust of eastern California and Nevada fractured into a series of faults that subsided and sank into deep basins. The newly formed mountains around them started shedding sediments and volcanic materials into these basins, and ultimately thousands of feet of strata had accumulated. We divide the sediments at Zabriskie Point into three formations, the Artist Drive, the Furnace Creek, and the Funeral. The Artist Drive is mostly volcanic material, including ash deposits that weather and oxidize into a rainbow of bright colors (the Artists Palette is a popular site for viewing them). The 6 million year old Furnace Creek formation, composed of clay and silt deposits, tends to weather into badlands, barren gullies that support little in the way of plant life. The Funeral formation includes sand and conglomerate formed in large alluvial fans, as well as basaltic lava flows.
The three formations that I've described above are the kinds of rocks one would expect to find deep in the accumulated sediments of a graben like Death Valley, where they would mostly be deeply buried and hidden from view. But geologic events conspired to push these rocks upward: the direction of the extension changed, and a new graben, that of Death Valley, began forming about 4 million years ago. The rocks in the Furnace Creek graben were twisted and faulted upward, and erosion began to tear away at the newly exposed rocks. These were the rocks that lined the highway that we followed into Furnace Creek, and we stopped in several places to have a look.
Part of the intense interest in these rocks lay in the fact that they held vast amounts of borate minerals, a rare commodity in the late 1800s. The discovery led to the exploration of Furnace Creek and the establishment of many mines in the area. The Furnace Creek Resort complex was an outgrowth of the mining boom, and the trademark "20-Mule Team" Borax originated with the wagons that carried the minerals 150 miles to railroads near Barstow. Some of the mines were still active just a few years ago (the mineral claims were grandfathered in when Death Valley became a park).
The rocks are always interesting to see, but the ongoing rain left the slopes wet, which seemed to intensify the color. It's true that I would have preferred slightly more bland coloration in favor of a sunny day, but here in my armchair several weeks later, I can deeply enjoy the color show, and the privilege of watching streams of water flowing in the driest of American deserts.

Sunday, March 19, 2017

Spring is Coming, and Flowers are Awakening in the Sierra Nevada Mother Lode

It's still a bit early to see the awesomeness to come, but the spring wildflowers are beginning to make a splash of color in the Sierra Mother Lode. With the record and near record amounts of rain in Northern California, the slopes are primed to produce a wildflower show to compete with the "super-blooms" taking place in the California deserts this year. We were exploring a portion of the southern Mother Lode in the vicinity of Mariposa and Coulterville yesterday, and I took my attention off the rocks for a few moments to catch some pictures of the early-blooming flowers. Above is a Fiddleneck (Amsinckia species), often one of the first of the wildflowers to bloom in this region. It can be poisonous to livestock, and yet was used as a food and medicine source by Native Americans.
Near the Pinetree-Josephine Mine we saw a number of Brodiaea, or Blue Dicks (Dichelostemma capitatum). These beautiful flowers grow from bulbs that were also an important source of food to the Native Americans of this region.
I don't know as many wildflower species as I should, as much as I appreciate their beauty. In a few places there were carpets of small yellow flowers (Goldfields, in the Lasthenia genus, thanks to Siera Nystrom in the comments).
Seeing some of the flowers growing in the usually poisonous serpentine soils reminded me that it is time to head up to the Red Hills soon, a Mother Lode locality known for a large number of endemic species.
As per Jane Strong in the comments, Orobanche fasciculata, clustered broomrape. Thanks for the identification!
And finally, the ever-present and always beautiful Indian Paintbrush (Castilleja species). There are some 200 species of this flower.

This is only the very beginning of what promises to be a wonderful year for wildflowers. I hope to be bringing many more such scenes to your attention in coming weeks!

Monday, March 13, 2017

New Exhibit at the Great Valley Museum: Homo Naledi and MJC's Dr. Debi Bolter

If you've read my blog for any amount of time, you know that I work in a wonderful Science Community Center, which has a the marvelous Great Valley Museum (the GVM) taking up most of the bottom floor. The museum has existed for more than thirty years, but spent most of that time in a cramped 1930's vintage house. It had been a dream for decades that the museum could grow into a larger facility, but it wasn't until about three years ago that it finally happened.

The museum is equipped with a world-class planetarium, a Science on a Sphere, a live animal exhibit, and a permanent set of exhibits on the natural history of the Great Valley. There is a nice storage facility and curation laboratory, and quite soon there will be an Outdoor Education Laboratory (you'll be hearing lots more about this part). It also has a large space for rotating exhibits, and I'm happy to report on the latest: A New Star in the Ancient Human Family: Homo naledi and Modesto Junior College's Dr. Debi Bolter.
You may have heard the news about the discoveries of a new Hominin species in the Rising Star Cave in South Africa. It was in the headlines in 2014, and was a cover story in National Geographic. Fewer people may realize the close connection between the discovery and one of the anthropology professors at Modesto Junior College. Dr. Debi Bolter was part of the team who analyzed the teeth and skeletal elements found in the cave.
Dr. Debi Bolter of Modesto Junior College

Denise Godbout-Avant has worked with MJC and the GVM for many years, and lately as a volunteer has been collaborating with Dr. Bolter and other professors across our campus to produce a comprehensive exhibit about the discovery of Homo naledi. I was privileged to be in attendance at a sneak preview of the exhibit this evening.
Denise Godbout-Avant, curator of the Homo naledi exhibit
One of the unique aspects of the exhibit has been the use of some very complex 3-D printing to produce very detailed models of some of the skeletal material discovered in the Rising Star Cave. It was one of the unusual aspects of the research that the programs for the detailed scans was made available freely to other researchers. Printing these bones is a long and arduous process undertaken by MJC professors Joel Hagen and Dave Martin. Richard Avant painted and prepared the samples, while a number of MJC students assisted in other aspects of the exhibit.
Homo naledi is the middle skull, with a modern human on the right

The geology of the site is an important aspect of the research, as the cave is uniquely inaccessible. The bones lie in a chamber at the end of the "Superman Crawl" and the "Dragon's Back", extremely narrow passageways that make the accumulation of the bones in the particular chamber somewhat of a mystery. How did they get in there? Did they crawl in? Were they thrown into the chamber? Was there another entrance at one time or another?
The Great Valley Museum is a scientific treasure in a region that is often lagging in scientific education. The people of our region voted to support science education when they passed a bond issue a decade ago that resulted in the construction of the Science Community Center and the expansion of the Great Valley Museum. If you have not yet had an opportunity to visit the museum and take in the exhibits and maybe even a planetarium show, now is a great time to stop by! Bring the kids, for there is plenty for them to do as well. Information on hours and location can be found on the museum website at Follow the GVM on Twitter at

Saturday, March 11, 2017

Liveblogging the Deluge: It Ain't Over 'til the Fat River Drains...A Six Month Flood is in Process

The flooding in California hasn't been in the news all that much of late, but that doesn't mean the threat is over. The atmospheric river storms that have been hitting the state like an out-of-control fire hose have been turned off for more than two weeks, and no storms are in the ten-day forecasts, at least not in my area along the drainage of the Tuolumne River.

Our local rivers haven't received the message yet.

We were at the Merced National Wildlife Refuge yesterday, and as we were leaving we noticed that the Mariposa Slough, a usually dry watercourse, was in full flood mode, flowing over Dan MacNamera Road. Off to the west, water covered a huge area (below).
Today I was back on my own river, the Tuolumne, where it flows out of the Sierra Nevada onto the Great Valley floor. It is still flooding, and has been since January 4 when the most damaging of the atmospheric river storms began battering the state (the current flow is more than 11,000 cubic feet per second). One might think that once the rain stops, so will the flooding, but the situation is not so simple.

In the days before gigantic dams were built on Sierra rivers, huge tropical rainstorms would drop prodigious amounts of rain in the mountains, and monstrous floods would spread out across the floor of the Great Valley, looking much like the scene above, but extending for three hundred miles north, as far as Red Bluff in the north valley. The water would take weeks to flow out through the Carquinez Straits into San Francisco Bay. The last storm that did this took place in 1861-62. The vast flood caused the state to move its capitol to San Franscisco until the waters subsided. Besides 1862, evidence has been uncovered of similar intense events in 212, 440, 603, 1029, 1418, and 1605 (sediments from storm runoff are preserved in ocean basins offshore of the state). That adds up to around a 0.3% possibility in a given year; not common, but enough that emergency providers have to seriously consider the possible effects.
The giant reservoirs that have been built along the major rivers of the Sierra Nevada represent our last line of defense against such floods. They are designed to capture the biggest surges in such storms, holding the water until it can be released at lower flow rates spread out over time. Most years the dams do their job well, but they can be overwhelmed, as they were in 1997 when there was widespread flooding across the valley. Which brings us to the current situation on the Tuolumne River.

Don Pedro reservoir can hold just over 2 million acre-feet of water. Because of the brutal drought of the last five years, the lake was allowed to collect and hold much of the runoff from the early season storms of November and December, and by the end of the year, the lake was beginning to fill. And then the big storms of January appeared in the long-range forecasts. Operators at the dam realized they needed to make more room in the reservoir, so they ramped up the outflow of the river to a near flood level rate of 9,000 cubic feet per second. It's not usually allowed to go higher because of a local quirk of the geology.

The Tuolumne River is trapped in a narrow channel all the way through Modesto downstream, and has little room to spread out over the valley floor. In some ways that is a good thing: downtown Modesto and other cities downstream can't be flooded by overflowing rivers the way it can happen in Stockton or Sacramento (these towns require extensive levees for flood protection). Others who live downstream are not so lucky, as higher flows translate to deep-water flooding within the narrow floodplain. The floods can also overwhelm levees downstream on the flatter parts of the valley floor around Patterson and Tracy.

The unique channel and bluffs along the Tuolumne originated in the Pleistocene ice ages. During the time of maximum ice advance the swollen river (average flow was several times what it is today) was full of silt and mud which was distributed across the Great Valley flow in a vast alluvial fan. When the glaciers receded, the rivers started flowing clear and the faster flows cut into the surface of the alluvial fan, forming the distinctive terraces that can be followed from the Mother Lode to west of Modesto.

So here's the tricky part: this wasn't just a few tropical atmospheric river storms that dumped incredible amounts of rain. Many of these storms drew in arctic air masses and tremendous amounts of snow now coat the high country of the Sierra Nevada. The snowfall has accumulated to record depths and now something like two million acre-feet of water now drapes the slopes upstream of Don Pedro. If you are keeping track of all the numbers, that's enough to completely fill the reservoir, which happens to be nearly full already.

We are facing a problem of water disposal not seen in modern times. The operators of the dam have to walk a fine line of preventing downstream flooding, but allowing for huge inflows of melting ice and snow in the coming weeks. The "fine line" included opening up the emergency spillway for the first time since 1997 and having the water rise to within an inch or two of overflowing in an uncontrolled manner. Outflow finally began exceeding inflow on the 25th of February, and the lake is now about 10 feet below the rim for the first time since January.

The threat is not so much more stormy weather (the rain season is tapering off now), but heat waves. It's going to reach 80 degrees around the valley floor next week, and the warm conditions are going to accelerate the rate of melting. So we can be sure that the water managers will be watching conditions carefully. I read that flows will continue at near flood levels for another three or four months!
My local stretch of the Tuolumne River (and the rest, of course) will be a changed place by the end of this extraordinary year. I will not be surprised if there are some new channels in a few places. Certainly the number of trees along the river will be changed. Several big ones on the Parkway Trail have already come down. A great many shrubs and thickets have been washed away as well. One very nice development is that the upstream sections of the river have been swept clean of the hated river hyacinth, an invasive species that has caused innumerable problems (I don't know the current situation with the hyacinth in the Sacramento Delta).

Learn more about the possibility of overwhelming atmospheric river storms here: USGS ARkStorm Report (PDF - 46 mb).

Thursday, March 9, 2017

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.