Here We Go Again: Yellowstone is Going to KILL US ALL! Wait a minute...

I'm going to start with the conclusion (I've highlighted some parts using the bold font):

Geological activity at Yellowstone provides no signs that a supereruption will occur in the near future. Indeed, current seismicity, crustal deformation and thermal activity are consistent with the range and magnitude of signals observed historically over the past century [Lowenstern et al., 2006]. Over the past two million years, trends in the volume of eruptions and the magnitude of crustal melting may signal a decline of major volcanism from the Yellowstone region [Christiansen et al., 2007; Watts et al., 2012]. These factors, plus the 3-in-2.1-million annual frequency of past events, suggest a confidence of at least 99.9% that 21st-century society will not experience a Yellowstone supereruption. But over the span of geologic time, supereruptions have recurred somewhere on Earth every 100,000 years on average [Mason et al., 2004; Sparks et al., 2005]. As such, it is important to characterize the potential effects of such events. We hope this work stimulates further examination of ash transport during very large eruptions.

The reason I am doing so is because the media is reporting on the body of the report that came out recently concerning the possible effects of a major caldera eruption at Yellowstone National Park. That means we are getting the usual headlines like:

If Yellowstone Supervolcano Erupts, Ash May Reach NYC

Yellowstone Supervolcano Eruption Would Doom the United States

Eruption of the Yellowstone Supervolcano will turn the US into a Third World Country

Eruption of Yellowstone supervolcano could spell the end of the US

For the most part, the reports themselves aren't too bad (there ARE exceptions). The thing is, we've always known that a Yellowstone caldera plinian supereruption would be devastating. That's old news. The purpose of the research was to model the potential effects of such an event. I get that disaster and omens of disaster are what sell newspapers or put eyes on advertising, so headlines go over the top, just like they always have. But this approach leaves the readers with the wrong impression, and they are going to worry about whether eruptions of Yellowstone need to be added to their fears of terrorist attacks, Megalodon shark attacks on their Caribbean cruise, or whether vaccines cause autism. In other word, useless levels of stress based on incorrect or blatantly wrong information.
 
I want to send kudos to a couple of media outlets with less sensationalistic headlines, such as those from the Billings Gazette: Researchers predict ash fall if Yellowstone supervolcano erupted or the Daily Digest: New computer models show likely fallout of a volcanic eruption in Yellowstone.
These kinds of headlines actually communicate accurate information without the terror-inducing yellow journalism.

This report from the U.S. Geological Survey serves a useful purpose. It is part of the kinds of research that can help cities, states, and nations plan for and cope with natural disasters when they occur. The authors were careful to state in their conclusions the extreme unlikelihood of a rhyolite caldera eruption, but their computer model might be useful in predicting the effects of lesser eruptions elsewhere in the world, eruptions that are far more likely.

You can see the report here:
Mastin, L. G., A. R. Van Eaton, and J. B. Lowenstern (2014), Modeling ash fall distribution from a Yellowstone supereruption, Geochem. Geophys. Geosyst., 15, doi:10.1002/2014GC005469. 

But don't fret. There are still the Yellowstone WOLVES to worry about!

"Supervolcano" Causes Road to Melt! Hmm, About That...

"Parts of Yellowstone National Park closed after Massive Supervolcano beneath it melts road!" screams the headline in a typical treatment of a modest story out of one of our nation's premier national parks. Let's take the fact that there was a modest sized earthquake a few months ago, and add a video of bison running away from (actually trotting towards) Yellowstone, and you have the makings of a huge non-story. The world is going to end because the "supervolcano" is going to explode and kill us all!

Is the story wrong? In a tortuous sort of way, the story is "accurate". Yes, a road was closed "between" Old Faithful and Madison Junction, insinuating that a major throughway is blocked. It's actually a small side road. The melting of the asphalt was "caused by the massive supervolcano". Technically this is true. All of the geothermal features at Yellowstone are caused by the magma chamber of the "supervolcano",  which heats the groundwater, turning it to steam, which rises through the crust to melt asphalt. But asphalt can melt on really hot days in the desert too.

I don't know...I would think that the people who live and work on top of the gigantic "supervolcano" (more accurately termed a rhyolite caldera) would be a little more worried about their well-being if the volcano were about to blow. Instead, here is the original news release from the park: "Firehole Lake Drive Temporarily Closed" . You can just feel the barely restrained panic in the air... 

Geyser erupts on top of massive supervolcano!! Note the extreme panic in the crowd!

Yellowstone is a fascinating place  with a violent geologic history. But the last eruption was 70,000 years ago. Someday, most likely long after we are all dead and gone, it will erupt again. For the time being, nothing much is happening except for boiling and steaming water. Go see it. And try to ignore the screaming headlines, and enjoy the fact that we have such a fascinating place to see and visit.

The Airliner Chronicles: A Broken Land of Unspeakable Violence

That's an inflammatory title, and yet in the context of geology it is quite literally true. The land in today's picture is indeed broken, and was the scene of unspeakable violence 760,000 years ago. If such an event were to recur, it's a fair bet that civilization could end up in danger of collapsing into unrecoverable chaos.

Yellowstone National Park gets a lot of attention for being a "supervolcano", and numerous TV documentaries fan the flames of concern about the possibility of a giant eruption in the midst of our country. It's quite true that a full scale explosion like those that have happened three times in the last 2.1 million years could wreak havoc on a wide scale, but Yellowstone hasn't actually had an eruption in 70,000 years.

The proper geological name we geologists use for a "supervolcano" is rhyolite caldera. This works a little better because these calderas are not volcanoes in the normal sense of the word. They are gigantic holes in the ground caused by the collapse of the crust after vast amounts of magma are blasted into the atmosphere. Some calderas were singular mountains at one time (like Mt. Mazama, which collapsed to form Crater Lake in Oregon). Others weren't. They were volcanic centers that included a collection of smaller cones and lava flows. The collapse of giant calderas seem to begin with smaller eruptions that grow in intensity over a time scale measured in decades or centuries. That's why Yellowstone caldera is of somewhat less concern to geologists (that's not to say that lesser eruptions aren't impossible). What is less known to many is that we have more than one recently active rhyolite caldera in the United States; we actually have three. I got a close look at the other two on my plane flight in December.

My flight took a more southerly route than past trips, and as we crossed the crest of the Sierra Nevada, I realized I was flying directly over the north end of the Owens Valley and the Volcanic Tablelands. The Tablelands are the southeastern flank of the Long Valley Caldera, California's version of a "supervolcano". And if anything, it's more dangerous than Yellowstone, if for no other reason than the fact that volcanic activity is ongoing, even though gigantic eruptions like the one that rocked the region 760,000 years ago are unlikely.

The caldera itself was obscured by clouds, but I had a perfect view of the Tablelands, a region adjacent to the caldera that was covered by 400 feet or more of volcanic ash that was so hot when it landed that it welded itself into solid rock. The pink colored rock is called rhyolite tuff. The tuff from this eruption is called the Bishop Tuff.

The scale of the eruption is hard to imagine. For perhaps a week, huge explosions blew ash into the stratosphere. Not a little bit of ash; it amounted to around 150 cubic miles of ash. The ash buried the local landscape under hundreds of feet of hot steaming rock, while some ash deposits have been found as far away as Kansas and Nebraska.

The collapse of the caldera was a stupendous event as well. The hole was around 20 miles long and 10 miles wide, and as much as 1-2 miles deep (much of the caldera was filled with ash during the eruption itself as the ash column collapsed downwards). After 760,000 years, it is still plainly visible in satellite imagery and topographic maps (below).

After the eruptions ceased, water started to fill the caldera, eventually forming a 1,000 foot deep lake. The lake ultimately breached the margin of the caldera and rapidly carved a gorge hundreds of feet deep across the western edge of the Tableland. The walls of the Owens River Gorge expose a fine cross-section of the rhyolite tuff, allowing geologists to work out the sequence of events during the eruption.

Map courtesy of GeoMapApp

The Tablelands provide a window into the tectonic environment of the region. By covering the slope like a thick blanket, the tuff provided a blank slate on which post-eruption faulting can be easily seen and analyzed. There are dozens of faults, mostly trending north or northwest, with scarps that face west (the sunlit terraces) and east (the shadows). Geoblogger Callan Bentley provided a marvelous grounds-eye view of these faults in this post on his old NOVA Geoblog (Callan is now blogging primarily at Mountain Beltway under the auspices of the American Geophysical Union; he's always posting something interesting).

There is a much more extensive example of the broken nature of this landscape. The prominent mountain range on the upper right of the picture below is the White Mountains. In any other setting this mountain range would be a national park, but lying east of the Sierra Nevada, it sort of loses out. It tops out at 14,242 feet, rising as much as two miles above the adjacent Owens Valley. It is a gigantic fault block that formed when the land that is now the Basin and Range province began stretching and collapsing, forming a series of horsts (mountain blocks) and grabens (faulted valleys). The mountains lie in the rain shadow of the Sierra and never formed glaciers of any great extent. The highest arid slopes play host to the most ancient life on planet Earth: the Bristlecone Pines. The oldest Bristlecone is 5,062 years old. The Whites are a fascinating (and lonely) place to visit.

The Airliner Chronicles is one of my on-again/off-again serial features, which is usually updated whenever I fly somewhere.

Searching for the Lost (not actually lost) Dutchman (not actually Dutch) Mine: What a blast, literally

I've been to Phoenix quite a few times over the years, but somehow until last week had never taken Highway 88 to one of the most familiar sights in Arizona, the Superstition Mountains, home of the fabled Lost (not actually lost) Dutchman (not actually Dutch) Mine. It's probably fair to say that I wasn't trying very hard to find the legendary gold mine. I was having too much fun drinking in the stunning scenery and enjoying the fact that I was standing under a massive caldera ("supervolcano" in popular culture).

The Superstitions are...abrupt. The sheer cliffs are fascinating; they are composed of volcanic rocks that once made up the core of a vast caldera complex not unlike Yellowstone. Several massive explosions rocked the region, and so much ash was blasted out of the magma chamber that the chamber collapsed in on itself, forming a series of vast 'craters' 10-12 miles across. The calderas of the Superstitions are 15-25 million years older than Yellowstone, are extinct, and have been deeply eroded. The high peaks and spires were once part of the resurgent dome of the caldera.

As we drove east we reached the marginal area of the caldera, where vast blocks of tilted ash and tuff are exposed in deep rugged canyons. Highway 88, the Apache Trail, winds upwards from the Phoenix suburbs to a series of three reservoirs that were constructed a century ago to provide dependable water supplies for the vast city (it wasn't enough, though). The reservoir below is Canyon Lake, the lowest of the three. Thick rhyolite flows form the bold cliffs.

By the time we reached Fish Creek Canyon, the landscape had attained an other-worldly appearance. It seems just like the kind of place that one could hide...a secret gold mine! The Lost Dutchman Mine is the stuff of legend, as in it is probably more legend than fact. The Dutchman wasn't lost for one, and he wasn't a Dutchman, he was German. And as far as lost mines...the old miners left little to chance. There isn't much mineralization in the rhyolite tuff exposures, and since a few gold mines were developed around the margins of the old caldera, I'm willing to bet that the Jacob Waltz's mine was found long ago. But that's taking all the fun out of it, I guess.

Gold just doesn't grab me the way the imagination does...I stood among these rocks reliving the vast explosions that rocked this place, protected by the safe distance of time. Imagine an explosion so big that it incinerates all life for miles in all directions, a blast 500 times larger than the eruption at Mt. St. Helens in 1980. Imagine watching as the crust gives way and falls for one or two miles into the void. Imagine watching as the dust slowly clears away to a new and vastly changed landscape that will be void of life for years. Imagine as the volcanic activity in the caldera declines and ends, and over millions of years, the rocks are exposed by uplift, mountain-building, and erosion.

What an incredible place! Thank you dear brother and sis-in-law for the great trip!

The Other California: Why worry about Yellowstone? We've got our own "Supervolcanoes" to worry about

First off, let's get something straight. As far as geologists are concerned, there are no "supervolcanoes". There are stratovolcanoes, plug domes, cinder cones, and shields, but no "supervolcanoes". What the tv documentaries call a "supervolcano" wouldn't technically be a volcano at all, since it is a giant hole in the ground, not a mountainous feature produced by lava flows.

The volcanic features referred to as "supervolcanoes" are actually calderas, large, generally round depressions in the crust that form when huge eruptions of hot ash empty out magma chambers. The destablilized crust collapses inward to fill the void. Calderas form in a number of circumstances, and are not always catastrophic events. On the Big Island of Hawaii, for instance, the calderas on the summit of the vast shield volcanoes are just a few miles across, and are stable enough that the Hawaii Volcano Observatory is perched on the edge of one. On the other hand, the formation of some calderas is a catastrophe of almost unimaginable proportions. The eruption that produced the caldera at Crater Lake involved the extrusion of something like 25 cubic miles of ash, and turned the 11,000-12,000 foot high mountain into a gaping crater 4,000 feet deep, with a crater rim elevation of only 8,000 feet or so. The eruption was around 7,000 years ago, and human witnesses related stories of the eruption that have survived as myths into the present day. A similar-sized eruption in 1815 at Tambora in Indonesia caused food shortages in the northern hemisphere by blocking sunlight. Snow fell during the summer months, disrupting agriculture.

The ultimate in a caldera eruption, though, is one that forms over a rhyolite magma chamber. Rhyolite is a silica-rich magma that can be highly explosive. It is also pasty (highly viscous), and the magma chambers can grow to massive proportions, sometimes tens of miles across. Rhyolite magma underlies Yellowstone National Park, and eruptions produced 185 cubic miles of ash 640,000 years ago, 67 cubic miles of ash 1.3 million years ago, and a simply unimaginable 585 cubic miles of ash 2.1 million years ago. An eruption of that size in the present day would be a civilization killer by way of a more or less instant ice age and massive disruptions of agriculture worldwide.

Everyone (at least everyone on cable tv channels) seems worried that the Yellowstone "supervolcano" is going to explode and kill us all. But if you live in California, you have other volcanic catastrophes to worry about. But that's not what I'm writing about today. I want to talk about a giant caldera that is part of California's past.

Rhyolite and granite are the same rock, at least as far as composition is concerned. The difference between them is crystal size; granite has visible crystals of quartz, feldspar and mica, while the crystals in rhyolite are too small to see. The difference arises from the place where the rock cooled. Granite cools slowly over many years deep in the crust, while rhyolite cools in a matter of hours or days following an eruption at the earth's surface. The Sierra Nevada is justly famous for the extensive exposures of granitic rock that form the sharp pointed alpine peaks and deep glacial valleys. The range is essentially a 400 mile-long tilted block of the speckled rock. What intrigues me is that while all that granite was intruding into the crust 100 million or so years ago (actually from about 140 to 85 million years), there must have been quite a collection of volcanoes and volcanic features on the surface above, features that would have been removed long ago by erosion. Except in a few spots...

The Minarets are probably the most beautiful and spectacular mountain ridge in the state that is not protected in the boundaries of a national park or monument (It is however protected as a National Forest Wilderness Area). The peaks are familiar to travelers headed to Devils Postpile National Monument, as they pass a pullout called Minarets Vista as they cross the crest of the Sierra Nevada. Far fewer actually walk among the pinnacles and towers in the depths of the wilderness.
The rocks of the Minarets are clearly different than your "average" Sierra. Granitic rock doesn't usually have the dark tones that are characteristic of the Minarets and is not usually as "spiky" (is that a geology word?). A closer inspection of the rock reveals that they are metamorphic, that is, baked and pressurized. Usually such rocks are older than the surrounding granite, but research reveals that this is not the case here. The metamorphic rocks are roughly the same age as some of the surrounding granitic rocks. The rocks include ash flow tuffs and large chunks of various kinds of volcanic rocks. Chunks, as in pieces as much as a mile wide. Big pieces of rock that collapsed into an evacuated magma chamber. The rocks of the Minarets are the remains of giant caldera, as seen from inside the crust of the earth.

So...Yellowstone National Park is a really neat place to see an active caldera, and if the cable news channels are right, it will probably kill us all by erupting, I dunno, maybe in 2012, but what a cool idea to be able to explore a caldera from the inside out! And it has the added virtue of being absolutely extinct, so it won't destroy us and our society in a cataclysmic explosion (just 15 miles to the east, the news isn't so good; more on that later).

As noted before, the Minarets are easily seen from a distance at places like Minaret Vista, and a somewhat less visited view can be had from the Sierra Vista Scenic Byway on the west slope of the Sierra Nevada. The only good way to see the rocks themselves is to hike in. I did some hiking there in my pre-geology days, and would love to return!

R. S. Fiske and O. T. Tobisch, 1994, Middle Cretaceous ash-flow tuff and caldera-collapse deposit in the Minarets Caldera, east-central Sierra Nevada, California: GSA Bulletin; v. 106; no. 5; p. 582-593 (abstract here)

The Yellowstone Media Storm: We're all gonna die! Oh, well sure, but...

Is Yellowstone gonna blow? Sure. Will everybody die? Sure, absolutely. But there is pretty much no connection between the first question and the second. Yellowstone caldera will in fact erupt again some day; it's a forty mile wide caldera with a huge magma chamber miles deep in the crust. That's the reason there are geysers there, and all those hot springs. And everyone will die, eventually. That's kind of a rule about living. But worrying about whether I'm gonna die from an eruption at Yellowstone is so far down my list of concerns that I am more worried about being gnawed to death by a pack of angry prairie dogs. It could happen, but it is highly unlikely.
I'm writing on the subject because a commenter asked for my take on the news this week about the activity around the Yellowstone caldera (for the record, "supervolcano" isn't a geological term). My best advice, before I finish with my own two cent's worth, is to check out the Eruptions blog here and here. Erik Klemetti does some excellent analysis of the story and how quickly things can be overblown by a media that thrives almost exclusively on spectacle, and has little use for reasoned discussions of the actual risks.

As I considered the question of an 'informed' response, I had to wonder if I'm not guilty of the same sort of exaggeration and sensationalism of cable news and other media. In my pursuit of educating others, I am not above discussing lurid tales of death and geological mayhem. After all, when I talk about volcanoes in class, I lead with Krakatoa, Tambora and Pompei, and I discuss the potential effects of a gigantic rhyolite caldera eruption such as those that took place at Yellowstone three times in the last two million years (not to mention broadly equivalent eruptions at Valles Caldera and Long Valley Caldera). I have a clear conscience on the matter, because I follow up with a discussion of the actual risk and probability of such events happening to our time; an eruption like the Yellowstone Caldera happens somewhere in the world every few hundred thousand years. Smaller, but certainly dangerous eruptions like those of Tambora (1815), Krakatoa (1883) and Katmai (1912) happen somewhere in the world on a scale of decades. And when these events take place there are clear signals that something is about to happen.

So, the Yellowstone Caldera floor rose around a foot during the last decade (that's the caldera in the picture above; I was standing on one rim, the mountains in the far distance form the other rim). There was an intrusion, a sill, that was filling and inflating with magma. There is nothing unusual or particularly alarming about this, as Yellowstone is an active magma chamber, and such events are normal. Although it has been 70,000 years since the last eruption in the park (and more than 600,000 years since the so-called 'supervolcano' eruption), it could happen again, but any activity would be accompanied by many other phenomena that would provide plenty of information about the scale of the eruption and the hazard to people in the region. My take? Learn about Yellowstone; it is a fascinating place, worthy of our attention and worthy of protection as a crown jewel in our national park system. But worry about the end of civilization as we know it in a vast explosion of fire and volcanic ash? No, there are other problems that we need to think about.

The best quote on the matter? From Max Read at Gawker: "But who do you trust, some kind of "professor," or your overactive imagination?" To which I might add: "But what about professors with overactive imaginations?"