Back in 2005 a docudrama called Supervolcano explored what might happen if the caldera beneath Yellowstone National Park erupted today. It was riveting television and, according to most experts, fairly accurate in its portrayal.
Now comes word that Yellowstone's volcanic basement has risen by roughly 7 inches in the past three years as a result of a massive intrusion of molten magma about 6 miles beneath the caldera. That's evidence of the park's underlying volcanics, but not indicative of an impending eruption, according to University of Utah scientists.
"There is no evidence of an imminent volcanic eruption or hydrothermal explosion. That's the bottom line," says seismologist Robert B. Smith, a geophysics professor and lead author of the study published in the journal Science. "A lot of calderas [giant volcanic craters] worldwide go up and down over decades without erupting."
Just the same, the upward movement of the Yellowstone caldera floor is more than three times greater than ever observed since such measurements began in 1923, says the study published in the November 9th issue of Science by Smith, geophysics postdoctoral associate Wu-Lung Chang, and colleagues.
Conventional surveying of Yellowstone began in 1923. Measurements showed the caldera floor rose 40 inches between 1923-1984, and then fell 8 inches during 1985-1995. Now the caldera is once again on the rise.
"Our best evidence is that the crustal magma chamber is filling with molten rock," says Professor Smith. "But we have no idea how long this process goes on before there either is an eruption or the inflow of
molten rock stops and the caldera deflates again."
According to the university, the magma chamber beneath Yellowstone is a not a chamber of molten rock, but rather a sponge-like body with molten rock between areas of hot, solid rock. And it's really not that unusual for such chambers to expand and contract down through the years, as calderas such as Yellowstone, California's Long Valley (site of the Mammoth Lakes ski area) and Italy's Campi Flegrei (near Naples) rise and fall "repeatedly for decades to tens of thousands of years without catastrophic eruptions," according to the researchers.
Professor Smith and Chang conducted the study with University of Utah geophysics doctoral students Jamie M. Farrell and Christine Puskas, and with geophysicist Charles Wicks, of the U.S. Geological Survey in Menlo Park, Calif.
Yellowstone: A Gigantic Volcano Atop a Hotspot
According to Professor Smith, Yellowstone is North America's largest volcanic field. It was created by a gigantic plume of hot and molten rock that begins at least 400 miles beneath Earth's surface and rises to 30 miles underground, where it widens to about 300 miles across. There, blobs of magma or molten rock occasionally break off from the top of the plume, and rise farther, resupplying the magma chamber beneath the Yellowstone caldera.
Previous research indicates the magma chamber begins about 5 miles beneath Yellowstone and extends down to a depth of at least 10 miles. Without this heat source, Yellowstone's famous geysers, hot springs, and fumaroles would die off.
Now, according to Professor Smith, as Earth's crust moved southwest over the Yellowstone hotspot
during the past 16.5 million years, it produced more than 140 cataclysmic explosions known as caldera eruptions, the largest but rarest volcanic eruptions known. Remnants of ancient calderas reveal the
eruptions began at the Oregon-Idaho-Nevada border some 16.5 million years ago, then moved progressively northeast across what is now the Snake River Plain.
The hotspot arrived under the Yellowstone area sometime after about 4 million years ago, producing gargantuan eruptions there 2 million, 1.3 million and 642,000 years ago. These eruptions were 2,500,
280 and 1,000 times bigger, respectively, than the 1980 eruption of Mount St. Helens. The eruptions covered as much as half the continental United States with inches to feet of volcanic ash.
The most recent giant eruption created the 40-mile-by-25-mile oval-shaped Yellowstone caldera. The caldera walls have eroded away in many areas - although they remain visible in the northwest portion of
the park. Yellowstone Lake sits roughly half inside and half outside the eroded caldera. Many smaller volcanic eruptions occurred at Yellowstone between and since the three big blasts, most recently 70,000 years ago. Smaller steam and hot water explosions have been more frequent and more recent.
Measuring a Volcano Getting Pumped Up
In the latest study, the scientists measured uplift of the Yellowstone caldera from July 2004 through the end of 2006 with two techniques:
-- Twelve Global Positioning System ground stations that receive timed signals from satellites, making it possible to measure ground uplift precisely.
-- The European Space Agency's Envisat satellite, which bounces radar waves off the Yellowstone caldera's floor, another way to measure elevation change.
The measurements showed that from mid-2004 through 2006, the Yellowstone caldera floor rose as fast as 2.8 inches (7 centimeters) per year - and by a total of 7 inches (18 centimeters) during the 30-month
period, says Chang.
"The uplift is still going on today but at a little slower rate," says Professor Smith, adding there is no way to know when it will stop.
The professor says the fastest rate of uplift previously observed at Yellowstone was about 0.8 inch (2 centimeters) per year between 1976 and 1985. He says that Yellowstone's recent upward motion may seem small, but is twice as fast as the average rate of horizontal movement along California's San Andreas fault.
Computer simulations were used by the scientists to better determine what changes in shape of the underground magma chamber best explain the recent uplift. These simulations or "modeling" suggested the molten rock injected since mid-2004 is a nearly horizontal slab - known to geologists as a
sill. The slab sits within and near the top of the pre-existing magma chamber, which resembles two anvil-shaped blobs expanding upward from a common base.
Professor Smith describes the slab's computer-simulated shape as "kind of like a mattress" about 38 miles long and 12 miles wide, but only tens or hundreds of yards thick. In reality, he believes the slab resembles a large, spongy pancake formed as molten rock injected from below spread out near the top of the magma chamber.
While the scientists believe steam and hot water contribute to uplift of the Yellowstone caldera, particularly during some previous episodes, the latest evidence indicates molten rock is responsible for most of the current uplift.
Chang says that when rising molten rock reaches the top of the magma chamber, it starts to crystallize and solidify, releasing hot water and gases, pressuring the magma chamber. But gases and steam
compress more easily than molten rock, so much greater volumes would be required to explain the volcano's inflation, the researchers say.
The research was funded by the National Science Foundation, the U.S. Geological Survey and the Brinson Foundation.
(Much of the above text was prepared by Lee Siegel, from the University of Utah)
You can stay on top of Yellowstone's volcanic gyrations by visiting the Yellowstone Volcano Observatory.
Comments
gargantuan eruptions there 2 million, 1.3 million and 642,000 years ago. These eruptions were 2,500,
280 and 1,000 times bigger, respectively, than the 1980 eruption of Mount St. Helens
By these ratios, looks like we're due for another big one! But by these same ratios, is should only be about 85-100X the intensity of MSH in 1980. If that's any consolation to the locals.
Good thing these ratios don't mean much in real-time geological timelines or else those "the sky is falling" dooms-dayers would be all over this one. Or does this fall into the "ignorance is bliss" category?
Funny thing about volcanos......they're rarely, if ever, truly extinct. Extinct correctly describes the Dodo, among other flora and fauna too numerous to list. Dormant is a better assessment, since we don't have enough accurate historical data from which to render judgement on the difference between those two terms with any REAL certainty. Makes for the basis for some interesting speculation though!
I wouldn't put my condo on the market just yet Kurt.
Lone Hiker, in the Mammoth Lakes area (not far from Mt. Whitney) of California, the continuous seismic activity around this part of the country, where past volcanic activity was once quite prevalent, doesn't seem to bother the local residents...million dollar ski chalets, expensive townhouses and condo's. This is one part of the country I consider beach front property ready to be sold for a pittance once the smoke starts spewing. This is really beautiful volcanic country ready to explode someday. Once the big one hits...it's shake and bake! It's amazing where developers build homes in California...anything with a view and on a fault line.
Even more amazing are the people who purchase the properties. I admit to a certain wonderment (and lack of good judgement) about folks who desire "homes on stilts", precariously perched on mountainsides, just for the view! I've witnessed the results of mudslides carrying half-million dollar homes (25 years ago) into canyons in the Huntington Beach area. I know personally of 2 colleagues who own residences within a few hundred feet of "The Fault" just north of San Jose, because "it was all we could afford at the time", like these properties were somehow "cheap". On the other hand, the history of the worst earthquake in modern history lies within the scope of the New Madrid Fault, running through a region that few people would take for "risky", right in the heart of the Midwest. But you won't deter development in St. Louis, Memphis Cincinnati, Indianapolis, Nashville or Little Rock anytime soon based on the notion that the area, currently seismically active or not, is an "at risk" zone. So why should attitudes in the Rocky Mountain region be any different, just because it's less populace?
As we all know, the most fertile soils on the planet are in the shadow of some of the most volcanically active mountains, and you'll never convince the under-developed nations that farming is too risky to conduct in those regenerating lava fields. I guess the underlying factor is that man will do as he sees best through his "blinders on" view of what needs to be versus what can be, even to the point of losing everything for short-term gain. But I don't see the current Yellowstone data as anything worthy of instituting a national, or even local panic.
One thing I heard Bob Smith say when I just happened to be in Canyon (on my hiker/biker trip) when the new educational center opened was that it's not possible to discern when the next eruption, if there is one, will be. One thing people seem to say is that because the last two eruptions had a consistent interval that this will have a consistent interval. No one can confidently draw that generalization from just a couple eruptions.
There are so many fascinating things to think about, though, with this volcano. Did you know the source of the hot spot beneath the earth extends actually as far away as Dillon, MT, for instance? Also, Smith suggested evidence is that the hot spot does not extend to the next layers of the earth as previously thought. So, what causes this?
It's really neat stuff to think about, that the earth moves up and down, that land in Yellowstone Lake appears and is covered by water depending on what the caldera is doing.
No one can really imagine what 2,500 times Mt. St. Helens is or what the ash would look like. Look at these images for examples.
Map of ash range
Graph of Explosion size
These kinds of forces are amazing. It puts our sense of conversation, of "saving the earth," of our political issues into perspective. If we live in a world where Yellowstone will explode, where the sun will one day give out, what is conservation and environmentalism about exactly? Perhaps, we need metaphors better than "saving the earth" (even for future generations). I think there perhaps are better ways to think of why we care about protecting thermal features than to preserve them for future generations. Isn't there something else behind it? Those are the sorts of things that the Yellowstone supervolcano makes me think about. That, and, it sure is pretty neat to say you've slept, eaten, peed, and made love on top of the bed of a volcano.
Jim Macdonald
The Magic of Yellowstone
Yellowstone Newspaper
Jim's Eclectic World
The Canyon Village Education Center has a nice exhibit on those ash volumes to help kids (big kids too) comprehend the size of such an explosion and the aftermath of the ashfall. I remember my geology professor in back in the fall of 1980 gave us each a small vial of MtStH ash to keep. I can't imagine having a whole yard full of it several feet deep...
If one goes and looks at the data since they have been collecting it, a clear pattern emerges. While yellowstone is known for it earthquake swarms, the magnitude of them has been increasing and becoming more frequent over time. Add to this the recent increased rate of magma rise and a clear picture forms. Its like a bellows or a pulse. The pulse is getting stronger and stronger each go. It is just a matter or time before it gives enough of a push to break the upper crust and release the pressure. The tale tale sign should be small releases of gas and water vapor. If the park starts to see new gysers forming on a level never before seen, then real concern will start. Once enough of the pressure is released the top crust will collapse allowing it to become placid enough to be broken and BAAM big explosion as the magma releases it pent up pressurized gases from thousands of years of build up. I have a feeling once you start to see this, it will be very short lived. A matter of days. One would actually see a dramatic deformation right before.
The difference between this and the other volcano you mentioned is the amount of pressurized gas. Because the top part of the magma chamber is really dense Hot rock rather than just magma, the pressure from the gas and vapor dissolved there would cause the explosion to be many times amplified. Everyone west of the mississippi should be very concerned if this thing starts to explode. In any volcano explosion there is not usually any tell tell signs that it gonna blow until right before it does. In fact, the only signs they get are rock deformation and swarms of earthquakes. The same thing that is happening with yellowstone, except because its such a large amount of rock, it seems to be taking the eruption longer to occur. Its already telling us it wants to go boom.
The public will never know about it until the very end. The news will start to report on the new gysers forming. What do expect them to do, evacuate half of america to the other half just to starve from lack of food due to a nuclear winter? Besides there wouldn't likely be enough time for that to occur any way. Once the event starts to happen, its a cascade. Thats why the scientist can say there isn't any evidence of an explosion anytime "soon". There won't be until its ready to go and by that time its too late. BUT! there is ample evidence that it WILL explode eventually otherwise there would be NO activity at all. The when is the question that is never answered except in the moment and only to say that it doesn't seem to want to explode anytime soon.
Its funny cause the interviewers never ask the "authorities" involved what exactly are the "Signs" of an explosion soon. They never ask that question. They also never address the issue of the magnitude of the quakes and deformation over time, both of those have been increasing dramatically with each event.