Exploring One of the World's Largest Volcanic Eruptions...Ever. And a Problem: Stuck Between a Volcano and a Hard Place

I've been more and more concerned about the public damage being done to the scientific community and larger society as politics has swirled like a tornado around global warming, climate change, and pandemics. Trust is eroding in some quarters, and I only see this leading to worse disasters in the years to come (and really, nearly a million Americans dead is a huge disaster, even though it unfolded slowly over two years; just imagine the impact if those people had died all on one day). This damaged social compact between those who do science and the society at large reminded me that it isn't the first time this kind of issue has affected the public, and a few years ago I wrote about it in a two-part series. Here, with some modifications and updates, is part one.

There is a story I tell on the first day of almost every class I teach. It's about a place filled with the evidence of one of the great explosions in Earth history, near Mammoth Lakes in the eastern Sierra Nevada. The students in the picture above are standing on the edge of a gorge that exposes some aspects of the explosion, but no one place reveals the full magnitude of what happened here. We made a number of stops many miles apart, but it's hard to comprehend the full scale of the blast. It's just too big.

About 760,000 years ago, a magma chamber composed of silica-rich rhyolite magma exploded in a titanic eruption that sent about 150 cubic miles (600 cubic kilometers) of ash across the western United States. Ash layers are still recognizable in places like Kansas and Nebraska, and in the immediate area around the blast, volcanic ash and tuff occur in deposits hundreds of feet thick spread over dozens of square miles. So much material was lofted into the atmosphere that the crust collapsed into a gigantic hole 10 miles (16 km) wide and 20 miles (32 km) long, and thousands of feet deep; it's called the Long Valley Caldera

For me, it took an overflight at 30,000 feet to even begin to see the full scale of the blast. Just about all the landscape in the picture above is covered with volcanic tuff. A freeway climbs the slope on the left side of the picture but is barely visible. I've added labels in the picture below to highlight the location of the caldera, which was obscured by clouds

Our field studies trip took us down the Owens Valley and some of the lands east of the Sierra Nevada crest, including this gigantic hole that actually breached the mountain wall. The lower section of the crest allows Pacific storms to blow through, dropping prodigious amounts of snow, especially on Mammoth Mountain, a volcano that developed on the edge of the caldera thousands of years after the climactic blast. Many thousands of years later, it was decided that this was a perfect place to put a ski resort.

The Owens River Gorge on the margin of the Long Valley Caldera.

The caldera filled with water, and for thousands of years there was a lake. Eventually it breached the south edge of the caldera and drained. The resulting Owens River carved a 400-foot-deep gorge in a short period of time (above), and the canyon walls provide a marvelous cross-section of the strange volcanic rock.

The edge of the Long Valley Caldera along the Sierra Nevada crest.

The caldera is a stunning place to visit and contemplate, but that's not actually the story I tell my students on the first day of most of my classes. The story concerns an incident at Mammoth Lakes dating from the early 1980s which still has huge implications in the present day. It's about civic responsibility and public safety in the face of deadly geologic hazards, and how geologists found themselves stuck between a volcano and a hard place. The purpose of telling the story to my classes is to highlight the danger of willful geological ignorance.

On May 18, 1980, Mt. St. Helens exploded with unexpected ferocity, killing nearly four dozen people. The U.S. Geological Survey was caught off guard in terms of predicting the moment of the eruption, as they did not yet understand the dynamics of Cascades volcanoes. Only a week or so later, a series of four magnitude 6 earthquakes struck the Mammoth Lakes region, injuring a number of people and causing several million dollars of damage. Many more earthquakes followed, and with the location of the epicenters being within the caldera, the geologists became concerned. They deployed more instruments in the region and discovered that the floor of the caldera had been rising, some 10 inches between 1979 and 1980. Even more disturbing was the discovery that the earthquakes were migrating, and becoming shallower, ultimately reaching a mere 7,000 feet or so beneath the surface. New steam vents were opening up (although geothermal activity has always been present). As I say to my students on their first day of class, "You've been geologists for 45 minutes now, what do YOU think was going on?"

The floor of the Long Valley Caldera with Crowley Lake, and Glass Mountain on the far rim of the caldera.

The people of Mammoth Lakes apparently only knew that they were getting a lot of earthquakes. There wasn't a lot of communication between the geologists who were researching the increasing activity and the government and emergency personnel responsible for the safety of the community. I imagine that this occurred (and still occurs today) because of the vast amount of uncertainty involved in predicting geologic events. Who would want to go out on a very long limb and suggest that a town could be on the cusp of a very dangerous, even catastrophic event? There was a fairly recent case of geologists in Italy who were jailed because they didn't predict a deadly earthquake.

At the time, the USGS had a warning system in place, with three tiers:

NOTICE OF POTENTIAL HAZARD-Information on the location and possible magnitude of a potentially hazardous geologic condition. However, available evidence is insufficient to suggest that a hazardous event is imminent, or evidence has not been developed to determine the time of occurrence.

HAZARD WATCH-Information, as it develops from a monitoring program or from observed precursors, that a potentially catastrophic event of a generally predictable magnitude may occur within an indefinite time (possibly months to years).

HAZARD WARNING-Information (prediction) as to the time, location, and magnitude of a potentially disastrous geologic event.

Give it some thought...given the intense geologic activity, what would you do? Would you notify the civic authorities? Would you go to the media? Is it possible that the media might report the facts as they are known, or would there be a tendency to go overboard on their coverage? Keep in mind the difference between 1983 and the present day when numerous cable news networks have to keep talking 24 hours a day. Or alternatively, would you keep things quiet, and hope that the geologic activity would die down without any catastrophes occurring? What happens if you quash your findings, and an eruption takes place? What is your liability in the deaths and injuries that result? Is there an easy answer here?

What would you do?

And what finally happened?

Find out in part 2!

(You can read the original post from 2015 here: Geotripper: The Sierra Beyond Yosemite: Exploring One of the World's Largest Volcanic Eruptions...Ever. And a Problem)

I'm Occasionally Reminded I'm Near an Extraordinary Mountain Range: John Muir's Range of Light

It was one of those rare days of winter in the Great Valley of California. Recent rains have tamped down the dust, and gusty winds chased away the omnipresent haze. As a result, I was treated to a view of the mountain range that I live next to, but rarely see: the Sierra Nevada, John Muir's Range of Light. It is such a rare view that I have to realign my internal geography to recognize the peaks on the skyline. It's a special view, though. Almost all the high peaks lie within Yosemite National Park, one of my most treasured places.

I hike almost daily on the Tuolumne River Parkway Trail which climbs a short bluff to bypass the town's small water treatment plant. On clear days I am treated to a view towards the Sierra Nevada to the east, and a portion of the Diablo Range of the California Coast Ranges to the west. The most distant peaks, Mts. Lyell and Rogers Peak, are 80 miles away as the crow flies, so the initial peak identification is daunting. The distinctive shapes of the peaks are clearer at extreme zoom, so in the top picture I can identify Mt. Maclure on the far right, Mt. Simmons near the center, and below Simmons, almost invisible, the summit portion of Half Dome in Yosemite Valley! Cal Topo has a marvelous tool for identifying landmarks, as you can see below.

Source: Cal Topo

Mt. Clark and Gray Peak are the prominent peaks in the picture below. They are part of the Clark Range, a high spur that lies a number of miles west of the main Sierra Crest.

The next picture reveals the peaks south of Maclure. The three prominent triangular peaks (properly called glacial horns) from left to right are Mts. Maclure and Lyell, followed by Rogers Peak. Rogers is the only peak that is actually on the Sierra Crest, although Lyell is only a fifth of a mile away (the crest being defined as the ridge that separates west-flowing stream from those flowing east into the Owens Valley).

The last picture reveals Merced Peak (under the left side of the bird flock). It is part of the Clark Range. The Tuolumne River flows in the foreground.

The cabin fever resulting from pandemic isolation and winter conditions in the mountains is intense. I'm really looking forward to a chance to get back up into the mountains come spring and summer. But it is always nice to get a reminder that the mountains are there.
 

For a Coming New Year of Challenges: River Otters!

There are so many challenges coming in this new year and the years that follow. Dealing with the worst pandemic in a century, protecting our democracy, and above all, working to mitigate the effects of climate change and global warming. Those of you on the front lines: you are making a difference. You may feel like you are burning out, but hang in there, and take a short sanity break. Here is something to help: River Otters (Lontra candensis).

We were towards the end of the Waterfowl Auto Loop at the San Luis National Wildlife Refuge, and I saw something dive into the algae-covered slough. Sure enough a fur-covered head popped up, and then another. They seemed as interested in us as much as we were in them. So here is a 90-second moment of Zen for a New Year. I hope that yours is as good a year as possible in challenging times.

A History of the Drought in Three Pictures.

 

Castle Crags on December 27, 2021

It's nice to be able to report some good news once in a great while. Global warming models for California paint a truly depressing picture going forward of crippling droughts, failing snowpacks, and many tough choices to make regarding water use. We've been living those models for the past few decades with a five-year drought ending in 2017, and one of the worst drought years in history just last year. We are coming to depend more and more on the occasional intense atmospheric river events to fill reservoirs in preparation for the dry years. They've been in short supply in recent years.

My family-related travels have encapsulated the story of California's precarious water situation. The pandemic had prevented many forays north to Oregon and Washington, but we managed a trip last April, and we just completed a rather harrowing trip today. These trips were a lesson in contrasts.

We always try to take a break at Castle Crags State Park near Dunsmuir and Mt. Shasta. The granite peaks are geologically the equivalent of the Sierra Nevada, but geographically they are part of the Klamath Mountains (which were displaced west from the Sierra millions of years ago). The Crags are shorter than the adjacent Sierra Nevada, but the loftiest peaks reach 6,500 feet, which allowed for glacial erosion during the Pleistocene Ice Ages.

Castle Crags on December 18, 2021

When we visited last April, the forest surrounding the crags was frighteningly dry (below). What should have been a damp forest floor with streams swollen by meltwater was like a tinder box waiting for the spark that would ignite an inferno. Like the rest of the mountains surrounding the Central Valley, the snowpack was gone, literally 5% of a normal year. 

When we left on our trip on December 18, things were looking up a little. There had been a surprising strong storm in late October that had dropped some snow on the mountains, but warmer weather had melted much of it. A dry November left the snowpack at 19% of normal.

Then a bunch of storms coincided with our trip plans. When we stopped in at Castle Crags on December 18th, there was a delightful cover of snow on the peaks (the picture above). It seemed a promising beginning of a decent snowpack.

We were in Seattle area at the beginning of one of the biggest snow events in the city's history. We left the city on freeways so covered in ice that the lane dividers couldn't be seen, and everyone guessed (only somewhat correctly) where those lanes were. Spinouts and accidents were everywhere, and it took us nearly four hours to go the first hundred miles towards the south. We eventually outran the storm but stopped for the night in Oregon were the storm caught back up to us. 

Our next day was 380 miles of icy anxiety, but luckily the roads were clear when we reached the top of the Siskiyou Mountains and Mt. Shasta. But what huge amount of snow had fallen! Looking at the top photo in the post, you can see the high peaks were literally coated in snow.

Castle Crags on April 23, 2021

In a more official vein, the Sierra Nevada had jumped from 19% to 159% of normal snowpack in the space of three weeks (below). We've received the 52% of the total amount of snow year, with three normally wet months to go. And at least two more storms are forecast in the next ten days. It's really good news, a possible respite from the long-term drought that has been gripping the region. But it's a real mess if you have to be traveling in it.

Source: Snow Pack Conditions - Snow Water Content Chart (ca.gov)

But the snowpack is not the whole story. Reservoirs across the state reached critically low levels in two years of drought (below), and it will take more than a couple of good storms to build them up again. A heavy snowpack is great, but warm periods can prematurely melt and evaporate the ice. I'm going to stay optimistic, but my mind is telling me that this is a respite, not a solution to our problems. If we get a good water year, we will still face imminent droughts and depleted groundwater reservoirs. We need to face the problems, and not put them off. 

Source: Interactive map of water levels for major reservoirs in California | American Geosciences Institute

But it sure was nice to see all that snow!

Hoping All a Peaceful Christmas and a Better New Year

Merry Christmas and Happy Holidays to all! As is my (sometimes neglected) tradition, I offer up a very big Christmas tree, the General Grant Tree in Kings Canyon National Park. The tree is so large (268 feet high, 40 feet across at the base) that it took three pictures for me to capture it.

I don't have a shot of the General Grant all dressed in snow, so here is another Sequoia after a surprise storm during an April trip some years ago.

The tree was declared by Calvin Coolidge in 1926 to be the nation's Christmas Tree. At an early ceremony, park superintendent Colonel John White said ""We are gathered here around a tree that is worthy of representing the spirit of America on Christmas Day. That spirit is best expressed in the plain things of life, the love of the family circle, the simple life of the out-of-doors. The tree is a pillar that is a testimony that things of the spirit transcend those of the flesh." 

Individual trees can live for several thousand years, but the genus has existed since the time of the dinosaurs. They once grew across the northern hemisphere until they were done in by the Ice Ages. They survive today in several dozen groves scattered across the western slope of the Sierra Nevada.

It has really been a tough couple of years with droughts and other natural disasters. I am especially mourning the loss of so many Sequoia trees to wildfires. In the last two years, some 20 percent of all the Sequoia trees on this planet were destroyed. As we celebrate the beauty of these wonderful trees, we must acknowledge our role in their destruction, through climate change and misguided management of the groves. A horrible loss but the trees persist through it all.

It's odd to write of loss and tragedy in a post about a "happy" holiday season, but this holiday season has that sense of gloom and loss as well. I'm seeing people I've not seen in a long time, but we've had to be very careful, and the potential for tragedy continues in the form of a tiny but virulent virus that is surging for a fourth time. There is loss, but there is resilience as well, and that is my hope for all of you that you'll discover joy despite the losses we have all experienced.

I wish a wondrous season to you all!

Sure It's Safe...Until It Isn't. Don't be a Scour Critical Bridge

 

Source: https://hickmanbridge.com/#

It's a bridge. Just like tens of thousands of other bridges across the country. It was pretty modern when I moved to my little town in the Great Valley of California. It crosses the Tuolumne River about 12 miles upstream of Modesto, and it's a fairly important transportation corridor that carries a lot of traffic including heavily loaded gravel trucks from the quarries upstream. And it's home to dozens of White-throated Swifts, European Starlings, and apparently 6,000 bats!

But I've been here for 30 years, which means the bridge is more than half a century old, and...it has a problem. A serious problem, a major vulnerability. In fairness in case you are worried, there's no disaster coming later in the post. The bridge didn't collapse or anything. But time (and a couple of major floods) had revealed an important structural deficiency. It is a "scour critical" bridge. You really don't want a bridge that is scour critical. It is the underlying cause in more than half the bridge failures in the United States.

The picture above was apparently taken in 2017 when the river last flooded (I kind of miss the days of too much water compared to what we have now). Notice how the columns are all under water. There are some pretty powerful currents coursing around the bridge supports.

Now, take a look at the bridge in low-water conditions (above and below). The columns supporting the bridge are connected to concrete pads. The foundation extends 16 feet into the ground, which consists mainly of loose river sediment (although there may be some fairly solid sandstone too, but I don't have access to the geological reports from the engineers for this project).

Major floods in 1997 and in 2017 apparently scoured out much of the sediment surrounding the columns, and threatened to destabilize the entire bridge (I recall the bridge being closed for many days during both floods).

The problem became pronounced enough that an attempt was made to reinforce the foundation with concrete Tetris blocks (below). 

As I became aware of the problem, the old bridge began to look more and more delicate and fragile. I had been driving over the bridge for three decades without giving a second thought to the safety of the span, and did not learn the details of the threat until signs suddenly appeared on the river trail announcing the closure of a section of the trail for the next three years (in 2019), and a bunch of beautiful old oak trees were unceremoniously chopped down. They were beginning construction of a new bridge.

The construction crews quickly built a temporary trestle just above river level (betting against another 100-year flood during the construction period). It was strong enough to hold up to three gigantic cranes at once. The new bridge is going to be wider with bike lanes and a pedestrian walkway (the old bridge was rather terrifying to walk or bike across). But most important, the bridge will be supported by pairs of columns that will extend more than 100 feet into the riverbed and into the bedrock below. Scour will no longer be a serious threat.

The new bridge was constructed rather quickly all things considered, and is opening for business just three days from now. The old bridge was shut down permanently about 10 days ago. The photo below is a webcam image from November 17.

Source: https://app.oxblue.com/open/stancounty/hickmanbridge

The bridge is going to always have an odd alignment, as it would have been economically disruptive to remove the old bridge first and then build the new one over a three year period. I am now extremely curious how they will proceed with the demolition of the old bridge. There is nothing in the promotional materials that indicates how they will do it. It seems unlikely that they'll blow it up, considering the proximity of the new bridge to the old one. Their timeline suggests six months or so to accomplish the task. Geotripper will be there to report if anything interesting goes on!

When I photographed the bridges side by side the other day, I was struck by the degree to which the old bridge sags. I had never really thought about it before, wondering if that was originally part of the plan, or did it 'sink' a bit over the years. It bothers me a little not knowing the answer!

There was a huge political scuffle over the infrastructure bill that was recently passed into law over the objections of one major political party (they even want to punish the 13 members of their party who voted for it),. There are tens of thousands of structurally deficient bridges all across our nation that are 'safe until they aren't safe'. This particular bridge didn't collapse as it could have, but there are many, many others that are more dangerous than we collectively think. We drive over them every day, never knowing about the cracks in the concrete, and the rusting superstructure that holds the bridges together. This new investment in our country's infrastructure should have been implemented years ago, but I'm glad we got it through when we did. We deserve better from those who would 'serve' over us.

"What We Find Belongs to the Public Domain of Science": The Boy Paleontologists and the Irvingtonian Land Mammal Stage

 

Mission Peak from the Sabercat Trail in Fremont, California

I can just hear the script writers arguing about one of the scenes in an Indiana Jones movie...

George Lucas says "How about 'What we find belongs to the public domain of science'?"

Someone, presumably Harrison Ford in disguise says "George, you can type this s**t, but you sure can’t say it.”

Someone else pipes up and says "Shorten it to 'That belongs in a museum'" and history was made.

I'm sure it never happened that way, but "What We Find Belongs to the Public Domain of Science" was in fact the motto of the Boy Paleontologists, who prior to last weekend I had never heard of. As adventurers, they were far more real than Indiana Jones, and ended up contributing far more to science than a glorified tomb raider. And to my surprise, I learned a lot more in an unexpected moment of serendipity.

Interpretive sign on the trail describing the paleontology efforts at Sabercat Trail

To begin with, Irvington simply is not a city that I've ever heard of in California. There's Irving, Texas, and Irvine, California, but no Irvington. But there is a part of the geological time scale called the Irvingtonian North America Land Mammal Stage. And that means there's an Irvington somewhere in North America, but a moment of research reveals that there are hundreds of fossil sites of Irvingtonian age scattered across the continent (and in fact the world). I never really thought to look up the actual location (and yes I see that Irvington, NJ is a place). 

The Irvingtonian North American Land Mammal Age (NALMA) on the geologic timescale spans from 1.9 million to 250,000 years ago. The Irvingtonian is usually considered to overlap the Lower Pleistocene and Middle Pleistocene epochs (basically the middle of the ice ages). The Irvingtonian is preceded by the Blancan and followed by the Rancholabrean NALMA  (which I absolutely knew about; I wrote about it tangentially just months ago).

The beginning of the Irvingtonian is defined by the first appearance of Mammuthus south of 55° N in North America, and the beginning of the succeeding Rancholabrean is defined by the first appearance of Bison.

Source: Barnosky et al., Prelude to the Anthropocene: Two new North American Land Mammal Ages (NALMAs). The Anthropocene Review. 1. 1-18. 10.1177/2053019614547433.

So how do these land mammal stages happen? Basically someone finds a huge number of fossils in a particular locality, and the assemblage turns out to be correlated to lots of other fossil sites across the continent to the extent that any fossil site with the same assemblage can be confidently dated. 

My son has been encouraging me for months to come and visit and walk the path in a Fremont park called the Sabercat Trail. He said they dug up a bunch of fossils there and it was preserved as a historical park now. I was intrigued, but COVID cut down on the opportunities to visit so it didn't happen until last weekend.

We got there and I was confused. I was in Fremont, but I was in Irvington. It turns out that Irvington once did exist as a village, but it was incorporated into the larger city of Fremont, but retains its character as the Irvington Neighborhood. And suddenly I realized this Sabercat Historical Park was a lot more important than I took it for. It wasn't just a fossil dig, it was THE Irvingtonian fossil dig. And what a story it had!

The fossils were first reported in 1867 when a local dentist named Lorenzo Gordin Yates found bones on Mission Creek (Sabercat Historical Park is just a few blocks from Mission San Jose). He sent them to Yale University because there was no one yet on the west coast who could identify them. His samples apparently included horses, camels and mammoth bone fragments.

Decades passed, and despite being just a few miles north, paleontologists from U.C. Berkeley didn't visit the site until the 1930s. The head of the Paleontology department at Berkeley, Ruben Stirton collected an assemblage of fossils and published a report in 1939 that first referred to the Irvingtonian fauna. It was defined as a land-mammal age as a result of Don Savage's studies in 1951.

A very large mammoth tusk at the Bell Quarry. Source: Pleistocene Ecosystem (msnucleus.org) by Wesley Gordon

The Boy Paleontologists entered the scene in middle 1940s when Wesley Gordon brought his sons and several of their friends on a fossil-collecting trip to the site. By now the locality was an active gravel quarry (the mind reels at the number of specimens that must have been destroyed over the years). A weekend hobby turned into a major excavation using young volunteers from the local community. The digs continued for around 15 years, and were even the subject of a Life Magazine article. They ultimately recovered 150,000 specimens of 58 species. 

The site unfortunately lay in the path of "progress", or more specifically the 680 freeway. Most of the quarry is covered by pavement now, although the account mentions that Wes Gordon convinced CalTrans to slightly divert the route to preserve a Short-faced Bear locality. My son mentions that the Ohlone people fought a 20-year legal battle to preserve an ancient burial site from the same freeway.

What exactly did they find? Who was living in the San Francisco Bay region between 1.9 million to 250,000 years ago? The trail provides some very nice interpretations of the ecosystem that existed at the time.

The cast of creatures ranges from mammoths larger than today's elephants to frogs and toads. During the ice ages, San Francisco Bay didn't exist as such because sea level was hundreds of feet lower than today. The area was broadly similar to what it would be today, if not cooler and slightly wetter. The grazing animals were dominated by camels, horses, deer, mammoths, mastodons, peccaries, and a unique species of four-horned antelope first discovered at Irvington. There were also gigantic ground sloths many times the size of their cousins today in Brazil. Rodents and rabbits would have been as common as today, and their remains are part of the assemblage that was discovered. Because of the delicate nature of their bones, only a few birds, a Canada Goose and Mallard duck, have been found as fossils. There were undoubtedly hundreds of species as there are today.

The carnivores were diverse and imposing. Sabertooth cats have been found (hence the name of the park), as well as scimitar cats, dire wolves, coyotes, foxes, badgers, and raccoons. The most terrifying must have been the short-faced bear, which makes grizzlies look small. It is considered the largest terrestrial mammal carnivore known. 

The park is a different place today. Bobcats and coyotes have replaced the bears, wolves, and sabertooth cats. It offers a network of trails that wind in and out of Sabercat Creek, and there is a smaller wilderness area in adjacent Mammoth Creek. Most all the trails are paved and accessible except for the actual remains of the quarry overlooking the freeway. Most of the fossiliferous layers were eliminated by the construction of the freeway, but the view from that end of the park is far-ranging (below).

I have a feeling that the park is an underutilized birding site. 84 species have been reported so far, but that is probably far fewer than what is actually there, given the excellent riparian habitat. We saw 18 species during our short visit including a very accommodating Western Bluebird.

I'm glad my son dragged us out to the Sabercat Trail. It was quite a revelation and answered some questions I've always wondered about!