Volcanoes in the Mist (and underground): Travels in Death Valley

The Inyo Mountains, in any other setting in the world, would be considered a major mountain range, preserved as a national park perhaps, and celebrated as scenic wonderland. But just like an accomplished sibling overshadowed by a more famous brother or sister, the Inyos lie across the valley from the most spectacular part of the Sierra Nevada, and south of the higher White Mountains. For better or worse (mostly better), only a few roads penetrate the range, including the main western highway into Death Valley National Park, State Route 190. That was the road we followed on our recent exploration of Death Valley.

As was noted in the previous post, we attempted our trip during the Bombogenesis storm that wreaked havoc across Southern California. This kind of storm can often result in disaster as highways get closed or damaged by landslides, but we were lucky and were able cross the Inyo Mountains and Darwin Plateau without problems. But we did get the opportunity to see some great geology, and even were able to add a new stop to our itinerary (because we missed a different one, but I'm not complaining).

Our first sight as we approached the mountains was the snow covering the desert peaks (first picture above), a hint to the seriousness of the storm we were challenging. The tilted rocks are Paleozoic-aged (300-550 million years) limestone layers. They recall a time when California was very different, completely submerged under a shallow tropical sea. We would be seeing more of these fascinating rocks later on. The road crossed the flat uplands of the Darwin Plateau, and then plunged down a steep incline towards the Panamint Valley.

We actually had fog in this arid environment, since the clouds were crowding against the edge of the steep mountains. As we passed the Father Crowley Vista Point, the clouds briefly parted and we had a view into the deep gorge of Rainbow Canyon. At this point, the slopes and flats are covered with basaltic lava flows ranging in age from 8 to 4 million years old. The immediate question becomes, why volcanoes? Why right here?

In a sense, volcanism is possible almost anywhere on the planet. It's not that there is magma everywhere, but that a hundred miles beneath our feet there is a zone, the asthenosphere, where the rock is almost molten, but not quite (perhaps 5-10% liquid). To melt this rock and create volcanic activity would require raising the temperature (as happens at hot spots like Hawai'i), or releasing pressure (pressure keeps the rocks from melting in the same way that pressure cookers prevent water from boiling). There aren't any hot spots in the immediate vicinity, but the crust across the Basin and Range Province has been stretched and thinned, allowing pockets of basaltic magma to form and rise into the rocks above, often following fault zones to the surface.

Although we couldn't see it through the clouds, there are basaltic lavas across the Panamint Valley that are of the same age and the same exact composition as those at the vista point. In addition, the rocks across the deep valley have no obvious source (the picture below is from last year, a decidedly drier trip). The best explanation for these rocks is that the lavas flowed across an original surface that was later broken up by faulting when the Panamint Valley formed. Since the youngest volcanic rocks are just 4 million years old, the Panamint Valley is younger still. The Panamint Valley is more than a mile deep and 65 miles long! That's a lot of geologic activity in a short period of time.

Looking across the Panamint Valley towards Hunter Mountain. The dark rocks on the left summit area are identical to the rocks at Father Crowley Vista Point.

We made a stop along the road descending into the Panamint Valley to check out some spectacular exposures of the dikes and sills that once fed the eruptions of the basaltic lavas (most years we are in too much of a hurry to get a camping spot at Stovepipe Wells). The magma was following whatever weakness in the surrounding rock that could be exploited by the molten rock. In some cases, vertical fractures allowed the magma to rise, forming dikes. In other cases, the molten rock flowed between limestone layers, forming sills. This extraordinary roadcut (below) showed textbook examples of both kinds of intrusions in the same outcrop. The usually black basalt has been oxidized (rusted) to produce the strange reddish-brown color.

There's a saying that one should never blindly sit on the ground in the desert. There are just too many things with fangs, stingers, or spines. The barrel cacti were looking to grow quickly in these rare wet times!

We headed down the highway. We had reached Death Valley National Park, and we faced whatever Bombogenesis was going to throw at us...

Another Cool California Roadcut: Dike and Sill on Highway 190 near Panamint Springs

Dike (vertical brown rock) and sill (horizontal brown rock) along Highway 190 near Panamint Springs

I've been working through my memories of beautifully instructive roadcuts in California. Some, like the Big Pumice Cut and the Charlie Brown Outcrop, are quite famous to geologists and generations of field studies students. Others have received less attention, and today I'm showing a particularly nice spot to learn about the difference between a dike and a sill.

A dike is an intrusion of molten rock that is tabular (thin, but deep and wide, as it fills fractures in the rock), and discordant (it cuts across rock layers). A sill is also tabular, but it is concordant, meaning it squeezes between layers rather than cutting across like a dike.

Highway 190 provides access to Death Valley National Park from the west at Lone Pine and Olancha. It travels around the south edge of Owens Lake, and then crosses the Darwin Plateau before beginning a steep descent into the Panamint Valley. From there it crosses the Panamint Mountains at Townes Pass and enters into Death Valley.

The Darwin Plateau is capped with multiple layers of basaltic rock covering a sequence of Paleozoic limestone layers. Midway down the stretch between the turnoff to Darwin and the resort of Panamint Springs there is a spectacular exposure of a dike and a sill in the same roadcut. The basaltic intrusion has been weathered to an orange-brown color. The Paleozoic-aged limestone is gray and has clearly delineated layering that makes it a straightforward exercise to distinguish the two types of intrusions that cut through it.

I wish I could say that this is a favorite stop on our way to Death Valley, but unfortunately we are usually running late by the time we reach it late in the afternoon on our way to Stovepipe Wells. It is a marvelous example of both kinds of intrusions.

Where are the Ten Most Incredible Places You've Ever Stood? My Number 2: The Grandest Canyon of All

A clearing storm in Carbon Canyon, a tributary to the Grand Canyon

Of course, the Grand Canyon was going to appear on a list like this. It is one of the great spectacles of geology on planet Earth, and it has been entwined with my life many times over. I can trace the first inklings of my curiosity about geology to a vacation at the North Rim when I was a child of nine or ten. Picking up fossils in a meadow along the highway north of the park, I wondered how they could have ended up at 8,000 feet above sea level. A decade later I was a gawky thin teenager in his first year of college looking for direction in his life. A week below the rim on the New Hance and Grandview trails with an inspirational professor provided the impetus for following a career in geology. And then there has been the nearly three decades of leading students to this stunning place, introducing them to this most incredible gorge and the geological history it reveals. Yes, the Grand Canyon is one of the ten most incredible places I've ever stood.

The Desert View Watchtower on the eastern edge of the South Rim of Grand Canyon.

But there is a problem with picking the Grand Canyon as one of my "spots". It's a really big place! There are 200-plus river miles, the canyon is a mile deep and ten or fifteen miles wide, and has countless side canyons and tributaries (so many that a lot are named after their mileage along the river, i.e. Two-hundred Mile Canyon). Many of the side canyons would be national parks of their own in any other setting; Havasu Canyon and National Canyon are tens of miles long, and just as deep as the main gorge.

Mather Point, possibly. I didn't label this one!

So do you pick the rim? This is where most people see the canyon for the first time. There are two rims of course, the North and the South. Probably 90% of the park's visitors come to the South Rim, and that is where most of the facilities are located. It has some grand viewpoints, including, um, Grandview Point. I love visiting there, but it isn't the most incredible part I've stood on.

The North Rim is distinctly different. A thousand feet higher than the South Rim, it is covered with an extensive cool forest of fir and ponderosa. It's lonelier, with a single resort, a small camper store and a campground (check out the excellent Geogypsy Traveler blog for the perspectives of a North Rim ranger). No matter where I am on the North Rim, it feels more wild. It's one of my most cherished places in the world. But I can't pick out a single spot that I've stood on that set it apart from other areas of the canyon.

There are the archaeological sites. People have lived on and in the Grand Canyon for more than 4,000 years, and have left behind intriguing clues about their lives and beliefs, including the split-twig figurines and multitudes of petroglyphs and pictographs. Had I not ended up a geologist, I would most certainly have followed archaeology as a career. The Grand Canyon has some great archaeology, but I couldn't pick a single spot that represents all the canyon means to me.

It took a lot of consideration, but in the end, I knew the "spot" would have to be Hance Rapids at Mile 77 on the Colorado River. So many things in my life converged at this spot. The New Hance Trail reaches the river at this point. I walked the trail in 1976 on my first geology field studies trip and stood on the shore of the Colorado River for the first time. I had walked through 1.7 billion years of earth history to reach this spot, seeing the rocks I had been studying in class for the previous two months. The history of the canyon came alive to me as I walked in wonderment, seeing the crossbedding in sandstone caused by wind blowing over dunes 300 million years ago, the footprints of pre-dinosaurian reptiles and amphibians, the ripplemarks of long-gone rivers and beaches, and fossils from times before multicelled life existed on the planet.

It is at this point that river-runners first encounter the Granite Gorge, the Inner Canyon of the Grand Canyon. The rocks are schist and gneiss 1.7 billion years old  that formed in the roots of a long-gone mountain range that until recently was hidden in the deep crust of the lithosphere. Only in the last five or six million years has the Colorado River exposed these rocks to view. It was near this spot that John Wesley Powell wrote his immortal words about the Grand Canyon: "We are now ready to start on our way down the Great Unknown...We are three quarters of a mile in the depths of the earth...We have an unknown distance yet to run, an unknown river yet to explore. What falls there are, we know not; what rocks beset the channel, we know not; what walls rise over the river, we know not."

The Great Unconformity separates these ancient rocks from the only somewhat younger rocks of the Grand Canyon Supergroup (the reddish sediments on the right in the picture below).  The Supergroup is a group of late Proterozoic sediments that are three times as thick as the main sequence of Paleozoic rocks that make the upper 4,000 feet of the Grand Canyon cliffs. They were faulted, tilted, eroded, and ultimately buried by the advancing Cambrian sea of 515 million years ago. It may be the most famous unconformity on the planet.

This was the spot where I became a geologist.

I returned to Hance Rapids last summer for the first time in thirty years, only this time I came by raft rather than by foot. I am still processing that journey in my mind, but I already know that it was one of the most significant events in my life. I became aware of the fragile nature of life, first among the plants and animals in this challenging environment, but also of my own. Aside from the profound risk of driving a car every day, I came the closest I've ever been to realizing the possibility of death when I was dumped into the near freezing water and rode the toughest rapid for more than a quarter of a mile. We went over more than 150 rapids in seventeen days, and Hance was the first of the monster rapids, rated 8 or 9 on a scale of 10.

Some pictures surfaced a couple of years ago on my Facebook page of that first profound adventure that I had in 1976. It's remarkable how little the river and the rocks have changed, but I realized how much has changed in our understanding of how the rocks of the canyon accumulated, and how the canyon itself came into being. Plate tectonics had been accepted only a few years prior to my arrival in the canyon, and the tectonic history was only just then getting worked out. Parts of the story are still mysterious.

I also realize the massive changes in my own life since then. Back then, there was a dedicated geology professor discussing the history of the canyon, and a young man making life-changing decisions in the professor's class. The young man had not yet married, there were no children in his life, he had not earned a living on his own. He was just starting out.

Today, my kids are grown, I get awards for longevity at my job, and I'm closer to the end of my career than I am to its beginning. I am a teacher now, but I continue to be a student as well, seeking out new places, and revisiting the old ones from the past for continuing enlightenment. The canyon will continue to exist, changed only in a few ways during my tenure on the planet. It knows or cares little of the latest life form that scrabbles about its surface, and it will shrug off the gigantic reservoirs we've constructed to try and control the river.

The canyon is an incredible place. It gives us perspective in so many ways, and that's why it ended up as number two on the list of the most incredible places I've ever stood.

Just who is that thin person in the yellow jacket??

Into the Great Unknown: "Disaster" in National Canyon and the Volcanoes of Grand Canyon

Yeah, I was not feeling all that comfortable. It was day 13 on our journey into the Great Unknown, the Colorado River through the Grand Canyon. Day 13, and Lava Falls Rapid, the worst rated rapid on the river was...13 miles downstream. And I didn't know it yet, but we would arrive there at 13:00 hours. I'm not at all superstitious, but it was nice when the message written in the sands of time on the river shore appeared. Okay, I put it there myself, but I was apprehensive just the same!

We were camped at the mouth of National Canyon, which for many years was one of the larger and more popular campsites on the river. And then in the summer of 2012 it was hit by an apocalyptic flash flood that just about wiped the camp out of existence.

It's hard to imagine the scale of the flood. Estimates put the flow at 15,000 cubic feet per second. To put that into perspective, the flow of the entire Colorado River for most of our journey was around 8,000 to 12,000 cfs. And the flood was witnessed. A Western Rivers Expedition boat was passing by, and captured the flood entering the Colorado. Check out the video below by Joe Clark, one of the river guides:

Our campsite was rocky, but we found places to sleep. The rocky plain was barren of plant life. There is hope that a few artificial floods may ultimately deposit more sand on top of the bouldery deposits, but I wonder if the Bureau of Reclamation will be doing any artificial floods in light of the ongoing drought.

In any case, the experienced members of our crew were curious about how much the canyon above the river had been changed by the flooding. To me, the canyon was a beautiful place, regardless of how it might have once looked. How could I know any difference?

I could see that eroded ledges of Muav Limestone had indeed been buried in debris, and barely a single plant was visible along the course of the creek, despite the presence of a clear babbling stream. The going was tough in a few places. Boulders choked the channel.

The barren nature of the canyon was almost disturbing. It felt like there should be plants growing along the water. It drove home the point that no matter what ever else may happen, the rocks remain. Battered, broken, or polished smooth, they will last as everything else passes. But the rocks were also very beautiful, though, and the narrows spectacular. It occurred to me that this canyon, were it to be anywhere else in the country would be a national park or monument in its own right. Here, it was simply a tributary to the larger river, one of many.

The sun was high, and it was getting hot. We got onto the river and rowed downstream. We had reached a fairly long stretch with no major rapids, and lots of quiet passages through vertical canyon walls of Paleozoic sediments. In places we could see all the way to the canyon rim four or five thousand feet above us. The rim, and the world beyond, seemed remote and very far away.

I did a double take at Mile 176. Thousands of years ago massive landslide had broken away from the Supai cliffs out of sight above, and had come thundering over the Redwall Limestone, coming to rest near the river. It is called the Red Slide.

Over time erosion began to tear away at the debris-covered slopes, but here and there a large boulder protected the underlying soft material. The boulders were left standing on spires called hoodoos. It was yet another strange sight along the river.

I was on the lookout, because for the first time we would be seeing a new rock unit (the last "new" rock unit had been 100 miles upstream). It is not a familiar rock to the vast majority of visitors to the Grand Canyon, and in fact, most people are surprised to find out that such rocks are present in the national park: there are volcanoes and lava flows!

I looked high on the walls, and there was the first one, a fragment of black basalt clinging to the cliff. It was an exciting moment for me, because I've never seen these rocks before. I will deal with the profound effects of the lava flows in one of the next posts.

There were more signs of volcanism along the river where a sill had intruded into the Muav Limestone. It was one of the finer examples I've ever been able to photograph.
Soon we could see the source of some of the lava flows, a cinder cone on the high canyon rim called Vulcan's Throne.

We could also see the long tongue of lava from Vulcan's Throne that had reached the river. John Wesley Powell's description remains one of his most poetic writings:

Just over the fall a cinder cone, or extinct volcano, stands on the very brink of the canyon. What a conflict of water and fire there must have been here! Just imagine a river of molten rock running down into a river of melted snow. What seething and boiling of the waters; what clouds of steam rolled into the heavens!

And then, one of the strangest sights of all. A huge mass of congealed lava stuck right in the middle of the river. It was a plug of lava that filled the vent of one of the cinder cones. Called Vulcan's Anvil, it seemed like a message or a warning to river travelers, which indeed it is.

When we passed the anvil, we know we had less than a mile to one of the biggest challenges on the river: Lava Falls Rapid. The moment of truth had arrived...

The Anvil receded into the distance, and we prepared to scout the wildest rapid on a wild river.

Into the Great Unknown: Crossing the Great Unconformity Again; But Which One?

Every day is new. Every day the Canyon is different...

I look back over the notes of my journey down into the Great Unknown, the Colorado River through the Grand Canyon, and I am struck by the number of times I mention change. By mile 80 we had passed through essentially all the major rock units of the Grand Canyon, and one can be forgiven for thinking that things might get repetitious, but it just never happened. I was now fifty miles farther downstream, and every morning, every day produced new revelations. I knew by now on Day 11 that I was having one of the most incredible experiences I would ever have in my life, and still five days remained.

The day began as a sort of "passages" kind of journey. We needed to make 15 miles or so, and there was just one excursion up a side canyon in the plan. But there were also some big rapids to worry about, including Specter, Bedrock, and Deubendorff, as well as seven smaller ones. I could tell I was still a bit spooked after my swim down Crystal Rapid a few days earlier.

Enfilade Camp was on a sandy beach below a large terrace that promised a decent view. My nephew had hiked up the previous evening and had come face to face with a bighorn ram, so I was a bit curious to see what would be around in the morning. I found a nice view upstream and downstream, and a lot of sheep tracks and droppings, but none of them were visible (of course, given their excellent camouflage, they were probably there watching me).

We started the day in the Bright Angel Shale of Cambrian age, but before long we entered into the Granite Gorge again. It's interesting how we refer to the "Granite Gorge" when so much of it is actually composed of black schist. I was just stunned by the polished surfaces that looked all the world like obsidian, even on slopes dozens of feet above the river.

 The canyon walls closed in once again, and the schist cliffs rose high above us.

In eleven days we had dropped 1,200 feet or more, and the flora was picking up a definite Mojave-Sonoran flavor. Barrel cacti were common on the slopes above the river. Within a day or so we would be seeing ocotillo.

We reached Bedrock Rapid (6-8) and stopped to scout. It was appropriately named, as a big chunk of granite and schist split the river. If a boat went to the left, it would be caught in a too-small current and impossible eddy. But the river right tried to dash the boats against the rock outcrops. It took some hard rowing, but the boatmen got us through just fine. We bounced off a boulder, but it was done quickly and we were okay.

The river at Bedrock Rapid tries to mash my brother and sister-in-law against a cliff. I give them credit for carefully observing the geology.

Below the rapid I saw one of those extraordinary sights that seem to occur with continuing regularity. I've mentioned the Great Unconformity, and we saw a wonderful exposure in Blacktail Canyon, described in the previous post. The ancient erosion surface separates 500 million year old sediments from 1.7 billion year old metamorphic rocks.  It is marvelous to be able to lay one's hands on 1.2 billion years of missing history.

But the canyon hides secrets, and one of them is that rocks exist that fill that void. There are in fact lots of rocks, in layers about 12,000 feet thick. We had visited them earlier in the trip, in the area between Nankoweap and Hance Rapid. They too rest on a "great unconformity" spanning 500 million years. They in turn are overlain by the Tapeats Sandstone. Because the Supergroup has been tilted, they contact the rocks above at an angle, so this contact is known as an angular unconformity.

Above Bedrock Rapids, both unconformities could be seen in the same outcrop! The sun was at a difficult angle, so if you can't see it, take a look at the labeled version below. I've drawn this kind of rock relationship on chalkboards many, many times, but I haven't seen as many of them in the real world.

Downstream we encountered Deubendorff Rapid (5-8). As we bulled our way through, we caught the edge of a hole and lost an oar. Pete worked with the remaining oar, but got us through okay, if not a bit soaked.

Drifting along the river below, we encountered the second extraordinary sight of the day. Dikes and sills are the result of molten material forcing its way through solid rock. Dikes cut across the previously existing rock, while sills squeeze their way between layers. You can see examples of dikes, but few sills on my Geotripper Images website, and that's the thing: I don't have many pictures of sills.
As we came around the bend of the river, a black cliff came into view, a layer that ran parallel to the enclosing layers of Bass Limestone and Hotauta Conglomerate (these form the base of the Grand Canyon Supergroup). It was a basaltic sill of huge proportions. The precise name of the rock is diabase, which was a shallow intrusion that was neither extrusive in texture (fine-grained) or intrusive (coarse-grained). It's a grain-size in-betweener.

It was one more stunning sight in a canyon with many of them.

Soon after, the river re-entered exposures of the Granite Gorge Intrusive Suite, and the canyon narrowed. A lot. The walls of schist rose straight out of the river and soared for hundreds of feet. Just past Mile 135 we traveled through the narrowest gorge in the entire Grand Canyon, the Granite Narrows. It was only 76 feet wide. The river was over 100 feet deep!

It had been an incredible day, but the best part was just ahead. More on that in the next post!