Houston's Horrific Flooding: Thank Goodness It Can't Happen Here...Eh...Right? Think Again...

What's happening in Houston is beyond belief. And tragically, horrible flooding is happening now in southeast Asia as well, with at least 1,200 people dead. Although the extent of the damage in Houston is not yet known, meteorologists are already calling it unprecedented in American history. I can't begin to imagine experiencing feet of rain in the space of days, and it isn't over yet. My heart goes out to those in the midst of the disaster. It may take weeks for the waters to subside, and years for the region to fully recover.

This isn't Houston. It is our own much more modest flood a few months ago.

(I've abridged and adapted the following from a post in 2011)

Seeing events like this unfold on television or on the computer screen can provide a certain emotional distance from the full magnitude of what has happened. Thoughts develop along the lines of "Could it happen here?" and as we realize it might, we think "Are we prepared for an event like that?" Floods occur essentially everywhere, but the Central Valley (the GREAT Valley) is notable in the magnitude and frequency of its flooding. We had a experienced a few terrifying days in the early part of the year when it seemed that one of our largest dams, Oroville, was in danger of failing, and we have become aware that almost all our dams are aging, and need maintenance or replacement.  It makes one wonder how bad it could possibly get. Pretty bad, as it turns out.

Climate experts have been analyzing the possibilities that California could be hit by a devastating storm sequence that could leave much of the Central Valley as an inland lake. It sounds unlikely, at best a hypothetical model, but it has actually already happened. In 1861-62, a storm series dropped so much precipitation that a 300 mile long lake covered the valley, and forced the state capital to move operations from Sacramento to San Francisco for a time.

I mentioned Yellowstone in a while back, and it got me thinking once again about those things that are worth worrying about, those that are not, and those that are worth preparing for. Yellowstone last had an eruption 70,000 years ago, and the last major "supervolcano" (i.e. rhyolite caldera event) was more than 600,000 years ago. So how much should we worry about Yellowstone? It could happen, but not likely any time soon. But people are freaked out about the possibility if a quick internet search is any measure. They obsess about it, and even see strange conspiracies.

But what about a "superstorm"? People don't seem to worry about flooding so much, yet huge floods are a disturbingly common occurrence. 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 are beginning to seriously consider the possible effects. A report from the US Geological Survey talks about the potential for an atmospheric river storm they have termed an ARkStorm (Atmospheric River Storm). The possible effects make California's expected "Big One" earthquake look, well, medium in comparison. From the USGS ARkStorm Report (PDF download here - 46 mb):

The storm is estimated to produce precipitation that in many places exceeds levels only experienced on average once every 500 to 1,000 years. Extensive flooding results. In many cases flooding overwhelms the state’s flood-protection system, which is typically designed to resist 100- to 200-year runoffs. The Central Valley experiences hypothetical flooding 300 miles long and 20 or more miles wide. Serious flooding also occurs in Orange County, Los Angeles County, San Diego, the San Francisco Bay area, and other coastal communities. Windspeeds in some places reach 125 miles per hour, hurricane-force winds. Across wider areas of the state, winds reach 60 miles per hour. Hundreds of landslides damage roads, highways, and homes. Property damage exceeds $300 billion, most from flooding. Demand surge (an increase in labor rates and other repair costs after major natural disasters) could increase property losses by 20 percent. Agricultural losses and other costs to repair lifelines, dewater (drain) flooded islands, and repair damage from landslides, brings the total direct property loss to nearly $400 billion, of which $20 to $30 billion would be recoverable through public and commercial insurance. Power, water, sewer, and other lifelines experience damage that takes weeks or months to restore. Flooding evacuation could involve 1.5 million residents in the inland region and delta counties. Business interruption costs reach $325 billion in addition to the $400 billion property repair costs, meaning that an ARkStorm could cost on the order of $725 billion, which is nearly 3 times the loss deemed to be realistic by the ShakeOut authors for a severe southern California earthquake, an event with roughly the same annual occurrence probability.

If that doesn't sound like events in Houston, you haven't been paying attention. This is serious stuff.
Flooding rarely gets the epic movie treatment. Volcanic eruptions and earthquakes are so sudden and devastating; rising water just doesn't cut it as a drama setting. I haven't seen a lot of Katrina movies yet. But life isn't a movie. If you live in California, think for a moment about getting hit with a superstorm, and the delta and Central Valley ending up like this:It is a real possibility and a sobering thought....

By the way, not wanting to stir the pot (or maybe I do), if you are worried about Yellowstone erupting and you live in California, why aren't you giving more thought to our very own active rhyolite caldera, our "supervolcano"?

Maps and second photo from the USGS ARkStorm Report (PDF - 46 mb)

"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.

A Convergence of Wonders, Day 11: The Orange Steam is OK, but the Blue Stuff Will Kill You....

Say what? Oh yeah, I was once working on a series about our journey across the Pacific Northwest and the Northern Rocky Mountains in June called a Convergence of Wonders (the name derived from the influence of the Cascadia Subduction Zone, a convergent boundary). I had reached day 10 when we arrived and started exploring Yellowstone National Park, but was, uh, slightly distracted by another two week trip, a more personal trip. I'm home now, and I expect to wrap up this series now.

So what is today's title about? Well, the steam at Yellowstone National Park actually does have some bad stuff in it (high levels of carbon dioxide and hydrogen sulfide) and can cause some real problems for people with asthma and other conditions, but there is no blue steam or orange steam, except as it reflects the colors beneath it. The picture at the beginning is of Grand Prismatic Spring in the Midway Geyser Basin.

Yellowstone is justly famous for her collection of geothermal features; the 300 geysers in the park account for about two-thirds of all the geysers in the entire world. There are thousands of other fascinating geothermal features as well, including fumaroles, boiling mudpots and hot springs.

Fumaroles are steam vents. Sometimes fumaroles are short-lived features in the immediate aftermath of violent volcanic eruptions, but in places like Yellowstone (and Lassen Volcanic National Park in California) they are more permanent in nature. Sometimes they are transitional in nature, depending on the time of year and availability of groundwater. Some geysers erupt so rarely that they might as well be considered fumaroles that occasionally explode.

Boiling mudpots are cauldrons of hot acidic mud derived from the weathering of the surrounding volcanic rock. The bubbling mud above is the Fountain Paint Pot near the Lower Geyser Basin.

Hot springs are carefully defined as springs that have, uh, hot water. They are one of the most beautiful of Yellowstone's geothermal features due to the interplay of color caused by select absorption of sunlight and the presence of extremophile bacteria (which can survive in near-boiling water). Grand Prismatic Springs is one of the most spectacular features in the national park system, although it is hard to see except from above (there is a trail on the nearby hillside).

The hot spring we looked at in the last post, Mammoth Hot Spring, was a mountain of calcium carbonate derived from the solution of limestone layers along the pathway of groundwater movement. Most of the hot springs in the park are within a rhyolite caldera, and most of the springs have much less voluminous deposits made mostly of silica. White Dome Geyser, below, is the highest silica dome in the park at twelve feet.

No trip to Yellowstone would be complete without a visit to Old Faithful. At least that's what I've heard. I managed (quite on purpose) to miss two eruptions while we were there. There's just something about having amphitheatre seating and a giant crowd of people that is off-putting.

So what were these people standing around for? The rangers seemed far more excited about convincing people to see an eruption of Beehive. Is that it, that little bit of spray?

Oh, there it is! It produced a spectacular eruption!

As we started south to leave the park, we made a short stop at Grant Village to have a look at Yellowstone Lake, a huge body of water (132 square miles) that is the largest freshwater lake above 7,000 feet in the country, and possibly the world. The lake lies within the Yellowstone Caldera, and recent activity has caused parts of the lake bottom to tilt. Some shorelines are rising and others are falling.

I also took a moment to say hi to Nina Fitzgerald, a ranger at Yellowstone. She is a fellow geoblogger, and has been writing a great series of posts about her experiences in the park system. You can catch her work at Watch For Rocks.

We ended our day by traveling south along the Rockefeller Byway to Grand Teton National Park. More in the next post!

A Convergence of Wonders, Day 10: Exploring a Real Hot Spot

It was day 10 of our field studies journey through the Pacific Northwest and Northern Rocky Mountains. We had finally arrived at one of the flagship destinations for our trip: Yellowstone National Park! One of the crown jewels of our national park system, home of Old Faithful...we set aside two days to explore the park, and I did something slightly devious to my students. I spent the entire day looking at "not geysers"!

Frankly, I'm not sure any of the students noticed the distinction. That's the thing about Yellowstone; it is so full of wonders and curiosities that it would be a unique landscape to explore even if there were no geysers to be seen at all. We spent our day exploring the northern loop of the park, from Canyon Village and the Grand Canyon of the Yellowstone to Mt. Washburn and then to Mammoth Hot Springs. We stopped in at Norris Geyser Basin at the end of the day, but were distracted by a wolf.

It's funny about furry charismatic animals; they seem to trump the attention of everyone, especially geology students. Our first stop of the day had nothing to do with geology at all, it was to photograph an elk. One cannot travel fast in Yellowstone National Park, because there are constant traffic jams caused by tourons (tourist morons, including ourselves...) looking at bison, elk, bear, moose, beaver, or wolf. I was immune to the effect. I took only ten pictures of this particular elk...

We explored several overlooks at the Grand Canyon of the Yellowstone and Lower Yellowstone Falls. The colorful walls of the canyon are composed of weathered rhyolite just over 500,000 years old. This canyon has been cut very rapidly! 

Standing at the brink of the 308-foot-high Lower Fall of the Yellowstone, one can feel the powerful surge of the water as it disappears over edge. It's not hard to believe that such a deep canyon could be carved by a river like this.

The most astounding story to be learned at Yellowstone was never envisioned by those who established Yellowstone as our first national park in 1873 (Yosemite was set aside nine years earlier, but as a state park). We drove to the high ridge near Dunraven Pass and Mt. Washburn to have a look around.

There is a fable about several blind men who were touching an elephant and disagreeing about its nature, whether it was like a rope (the tail), a snake (the trunk), or a tree (the leg). Yellowstone's most striking feature was so big that it was decades before geologists recognized it for what it was: a vast caldera, the site of three of the largest volcanic eruptions to ever hit the North American Continent in recent geologic time (2.1 million, 1.3 million, and 640,000 years before present).

How big is the caldera? The snowcapped mountain in the distance in the picture below is Mt. Sheridan. We were standing on the side of  Mt. Washburn; there is a forty mile gap between the two. The mountain ridge that connected the two peaks sank into the caldera during a single massive eruption that put 600 cubic miles of ash into the atmosphere. The ash spread for thousands of miles. A repeat eruption would be devastating to civilization (despite what the television tells you, such eruptions are not imminent, nor are they overdue; we would see signs of caldera unrest dozens, if not hundreds of years beforehand). The source of these eruptions is thought to be a mantle hot spot, although there are several alternate interpretations.

Volcanism has been influencing events in the Yellowstone region for a long time. In early Cenozoic time, around 50 million years ago, the region was rocked by numerous eruptions that produced volcanic mudflows (lahars) that overwhelmed forests of sequoia/redwood trees (You thought they were found only in California didn't you? They were once much more widespread). Each time a forest was destroyed and buried, a new forest would grow in the sediments. That forest was destroyed in turn, and over time dozens of layers containing petrified logs accumulated. These forests are generally hard to access by road or trail, but one solitary upright trunk can be seen in the north part of the park. There used to be three here, but souvenir collectors carted off the others, which explains the prison in which the trunk resides.

We moved on down to Mammoth Hot Springs (with a few bear diversions), and took a look at the strange edifice of calcium carbonate. Most of the hot springs and geysers of Yellowstone do not produce massive mineral deposits, but they happened here, outside the boundaries of the caldera. Most of the water emerging from geothermal features in the park is charged with silica, but at Mammoth, the water has passed along faults that traversed Paleozoic limestones. The acidic waters dissolved the calcite making up the limestone, and when the waters emerged here, the calcite came out of solution.

The hot springs are constantly growing and changing location, so the deposits never look quite the same. Heat-tolerant bacteria provide a splash of color to the otherwise snow-white rock.

Spelunkers (cavers) will recognize many of the deposits, as they are similar to flowstone features found in many limestone caverns, especially the rimstone pools seen in the pictures below. Exploring Mammoth Hot Springs is kind of like exploring an inside-out cavern...

 The rimstone pools were especially photogenic...

There were several killdeers strolling across the pools...

We drove on in the late afternoon to Norris Geyser Basin, but I didn't get any pictures. We were distracted by the whole charismatic mammal thing anyway, the subject this time being a Canis lupus enjoying a meal in a meadow north of Norris.

You can see the whole wolf drama in this post.

We were done with another day...tomorrow would include the famous geysers (maybe), and Grand Teton National Park.

I've been posting regularly for the last ten days, but I am hitting the road again tomorrow, so the next few posts will be at unpredictable intervals, as web access will be tricky. Take care, all!

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)

Queensland's Flooding: Thank Goodness It Can't Happen Here...Eh...Right? Think Again...

Before you read anything else in this particular blog, go to the BBC news and look at 3 minutes and 46 seconds of stunning pictures of the extraordinary flooding this season in Queensland, Australia. The amount of water on the ground in the normally dry landscape is almost beyond belief. The BBC mentions a vast inland sea the size of France and Germany combined. My heart goes out to those in the midst of the disaster. This was an unusual train of meteorological events that ended a long drought, and culminated in the arrival of Cyclone Yasi, a category 5 hurricane. It will take weeks for the waters to subside, and years for the region to fully recover.

Not Australia, this is flood stage on our own San Joaquin in 2006

Seeing events like this unfold on television or on the computer screen can provide a certain emotional distance from the full magnitude of what has happened. Thoughts develop along the lines of "Could it happen here?" and as we realize it might, we think "Are we prepared for an event like that?" Floods occur essentially everywhere, but as I am based in California, my ears perk up whenever I hear about unfolding events along the Pacific coast. We had a pretty wild time of it in the last two months with serious floods in a number of areas, especially in southern California. It makes one wonder how bad it could possibly get. Pretty bad, as it turns out.

Those pesky climate experts have been analyzing the possibilities that California could be hit by a devastating storm sequence that could leave much of the Central Valley as an inland lake. It sounds unlikely, at best a hypothetical model, but it has actually already happened. In 1861-62, a storm series dropped so much precipitation that a 300 mile long lake covered the valley, and forced the state capital to move operations from Sacramento to San Francisco for a time.

I mentioned Yellowstone in a recent post, and it got me thinking once again about those things that are worth worrying about, those that are not, and those that are worth preparing for. Yellowstone last had an eruption 70,000 years ago, and the last major "supervolcano" (i.e. rhyolite caldera event) was more than 600,000 years ago. So how much should we worry about Yellowstone? It could happen, but not likely any time soon. But people are freaked out about the possibility if a quick internet search is any measure. They obsess about it, and even see strange conspiracies.

But what about a "superstorm"? People don't seem to worry about flooding so much, yet huge floods are a disturbingly common occurrence. 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 are beginning to seriously consider the possible effects. There was a bit of a stir in the geoblogosphere a few weeks ago about a report from the US Geological Survey about the potential for an atmospheric river storm they have termed an ARkStorm (Atmospheric River Storm). The possible effects make California's expected "Big One" earthquake look, well, medium in comparison. From the USGS ARkStorm Report (PDF download here - 46 mb):

The storm is estimated to produce precipitation that in many places exceeds levels only experienced on average once every 500 to 1,000 years. Extensive flooding results. In many cases flooding overwhelms the state’s flood-protection system, which is typically designed to resist 100- to 200-year runoffs. The Central Valley experiences hypothetical flooding 300 miles long and 20 or more miles wide. Serious flooding also occurs in Orange County, Los Angeles County, San Diego, the San Francisco Bay area, and other coastal communities. Windspeeds in some places reach 125 miles per hour, hurricane-force winds. Across wider areas of the state, winds reach 60 miles per hour. Hundreds of landslides damage roads, highways, and homes. Property damage exceeds $300 billion, most from flooding. Demand surge (an increase in labor rates and other repair costs after major natural disasters) could increase property losses by 20 percent. Agricultural losses and other costs to repair lifelines, dewater (drain) flooded islands, and repair damage from landslides, brings the total direct property loss to nearly $400 billion, of which $20 to $30 billion would be recoverable through public and commercial insurance. Power, water, sewer, and other lifelines experience damage that takes weeks or months to restore. Flooding evacuation could involve 1.5 million residents in the inland region and delta counties. Business interruption costs reach $325 billion in addition to the $400 billion property repair costs, meaning that an ARkStorm could cost on the order of $725 billion, which is nearly 3 times the loss deemed to be realistic by the ShakeOut authors for a severe southern California earthquake, an event with roughly the same annual occurrence probability.

Flooding rarely gets the epic movie treatment. Volcanic eruptions and earthquakes are so sudden and devastating; rising water just doesn't cut it as a drama setting. I haven't seen a lot of Katrina movies yet. But life isn't a movie. If you live in California, think for a moment about getting hit with a superstorm, and the delta and Central Valley ending up like this:It is a real possibility and a sobering thought....

By the way, not wanting to stir the pot (or maybe I do), if you are worried about Yellowstone erupting and you live in California, why aren't you giving more thought to our very own active rhyolite caldera, our "supervolcano"?

Maps and second photo from the USGS ARkStorm Report (PDF - 46 mb)

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?"