Yellowstone Volcano Observatory scientists answer questions about Supervolcanoes

USGS Yellowstone Volcano Observatory ^ | March 2005

[Strategerist]

BBC and the Discovery Channel produced a new docudrama and documentary about Yellowstone. The BBC version was shown in March and the Discovery Channel version will be shown on April 10th.

The docudrama Supervolcano dramatically explores the impact of a large caldera-forming eruption at Yellowstone. The scale of the portrayed eruption is similar to the eruption of the Huckleberry Ridge Tuff at Yellowstone 2.1 million years ago. The movie is realistic insofar as depicting what could happen if an eruption of this magnitude were to occur again. Although the drama is set in the future, it does an acceptable job of addressing some of the issues scientists would grapple with if Yellowstone showed signs of an impending eruption. The questions and answers below shed light on issues related to volcanism at Yellowstone. A much more detailed discussion, including full-color illustrations, can be found in U.S. Geological Survey Fact Sheet 2005-3024, available online at http://pubs.usgs.gov/fs/2005/3024/.

QUESTION: What is the chance of another catastrophic volcanic eruption at Yellowstone?

ANSWER: Although it is possible, scientists are not convinced that there will ever be another catastrophic eruption at Yellowstone. Given Yellowstone's past history, the yearly probability of another caldera—forming eruption could be calculated as 1 in 730,000 or 0.00014%. However, this number is based simply on averaging the two intervals between the three major past eruptions at Yellowstone — this is hardly enough to make a critical judgement. This probability is roughly similar to that of a large (1 kilometer) asteroid hitting the Earth. Moreover, catastrophic geologic events are neither regular nor predictable.

QUESTION: What is a "supervolcano"?

ANSWER: The term "supervolcano" implies an eruption of magnitude 8 on the Volcano Explosivity Index, meaning that more than 1,000 cubic kilometers (250 cubic miles) of magma (partially molten rock) are erupted. The most recent such event on Earth occurred 74,000 years ago at the Toba Caldera in Sumatra, Indonesia.

QUESTION: What would happen if a "supervolcano" eruption occurred again at Yellowstone?

ANSWER: Such a giant eruption would have regional effects such as falling ash and short-term (years to decades) changes to global climate. The surrounding states of Montana, Idaho, and Wyoming would be affected, as well as other places in the United States and the world. Such eruptions usually form calderas, broad volcanic depressions created as the ground surface collapses as a result of withdrawal of partially molten rock (magma) below. Fortunately, the chances of this sort of eruption at Yellowstone are exceedingly small in the next few thousands of years.

QUESTION: Is Yellowstone monitored for volcanic activity?

ANSWER: Yes. The Yellowstone Volcano Observatory (YVO), a partnership between the United States Geological Survey (USGS), Yellowstone National Park, and the University of Utah, closely monitors volcanic activity at Yellowstone. The YVO website (http://volcanoes.usgs.gov/yvo) features real-time data for earthquakes, ground deformation, streamflow, and selected stream temperatures. In addition, YVO scientists collaborate with scientists from around the world to study the Yellowstone volcano.

QUESTION: Do scientists know if a catastrophic eruption is currently imminent at Yellowstone?

ANSWER: There is no evidence that a catastrophic eruption at Yellowstone is imminent, and such events are unlikely to occur in the next few centuries. Scientists have also found no indication of an imminent smaller eruption of lava.

QUESTION: How far in advance could scientists predict an eruption of the Yellowstone volcano?

ANSWER: The science of forecasting a volcanic eruption has significantly advanced over the past 25 years. Most scientists think that the buildup preceding a catastrophic eruption would be detectable for weeks and perhaps months to years. Precursors to volcanic eruptions include strong earthquake swarms and rapid ground deformation and typically take place days to weeks before an actual eruption. Scientists at the Yellowstone Volcano Observatory (YVO) closely monitor the Yellowstone region for such precursors. They expect that the buildup to larger eruptions would include intense precursory activity (far exceeding background levels) at multiple spots within the Yellowstone volcano. As at many caldera systems around the world, small earthquakes, ground uplift and subsidence, and gas releases at Yellowstone are commonplace events and do not reflect impending eruptions.

QUESTION: Can you release some of the pressure at Yellowstone by drilling into the volcano?

ANSWER: No. Scientists agree that drilling into a volcano would be of questionable usefulness. Notwithstanding the enormous expense and technological difficulties in drilling through hot, mushy rock, drilling is unlikely to have much effect. At near magmatic temperatures and pressures, any hole would rapidly become sealed by minerals crystallizing from the natural fluids that are present at those depths.

QUESTION: Could the Yellowstone volcano have an eruption that is not catastrophic?

ANSWER: Yes. Over the past 640,000 years since the last giant eruption at Yellowstone, approximately 80 relatively nonexplosive eruptions have occurred and produced primarily lava flows. This would be the most likely kind of future eruption. If such an event were to occur today, there would be much disruption of activities in Yellowstone National Park, but in all likelihood few lives would be threatened. The most recent volcanic eruption at Yellowstone, a lava flow on the Pitchstone Plateau, occurred 70,000 years ago.

QUESTION: Because Yellowstone is so geologically active, are there other potential geologic hazards in Yellowstone?

ANSWER: The heat and geologic forces fueling the massive Yellowstone volcano affect the park in many ways. Yellowstone's many geysers, hotsprings, steam vents, and mudpots are evidence of the heat and geologic forces. These hydrothermal (hot water) features are mostly benign, but can rarely be the sites of violent steam explosions and pose a hydrothermal hazard. Earthquakes, another example of active geologic forces, are quite common in Yellowstone, with 1,000 to 3,000 occurring annually. Most of these are quite small, although significant earthquakes have shaken Yellowstone, such as the 1959 magnitude 7.5 Hebgen Lake quake, the largest historical earthquake in the intermountain region, and the 1975 magnitude 6.1 quake near Norris Geyser Basin. The many earthquakes and steam explosions in the past 10,000 years at Yellowstone have not led to volcanic eruptions.

[Strategerist]

The director of the YVO has recommended watching it so it can't be that terrible; on the Discovery Channel tonight at 8PM and 11PM EST.

[canalabamian]

Thanks for posting the times. Kiddos will enjoy it...and have bad dreams about volcanoes destroying the world. ;)

[cripplecreek]

Cool I love this stuff.

[Sundog]

Remember your Science Project?

[Sundog]

1/730,000 for any particular year?

The probability goes way up when it has been 760,000 years since the last one.

Who knows that math?

[Strategerist]

The probability goes way up when it has been 760,000 years since the last one.

It's been 640,000 years since the last one.

There have only been three supervolcanic eruptions at the present location of the Caldera; that's what's known as a dataset that's far too small.

In any event, the time between the eruptions is longer than the time since the last one, so Yellowstone certainly isn't "overdue" in any sense you look at it.

And it may never have another supervolcanic eruption. Hotspots tend to gradually go dead over time.

[muffaletaman]

Yellowstone's volcanism is only the most recent in a 17 million-year history of volcanic activity that has occurred progressively from southwestern Idaho to Yellowstone National Park.

http://volcanoes.usgs.gov/yvo/figures/fig1.html

At least six other large volcanic centers along this path generated caldera-forming eruptions; the calderas are no longer visible because they are buried beneath younger basaltic lava flows and sediments that blanket the Snake River Plain.

The Huckleberry eruption - 2.1M years ago - 530 cubic miles

Mesa Falls - 1.3M years ago (800,000yrs) - 60 cubic miles

Lava Creek - 640K years ago (660,000yrs) - 216 cubic miles

From the site above, there are seven different "hot spots" areas, and each probably had 2 or 3 eruptions over the last 17 million years. The hot spots trend northeast, over a trail about 350 miles long.

There is no sign they have ended.

[Polybius]

Cool I love this stuff.

Well, I'm too close.

I'd rather have something that eats Michigan instead. ;-)

[stevem]

Do we have a clue how many calderas there are in the world? This article cited Yellowstone and Sumatra. I believe the Bay of Naples in Italy is one. How many are there?

[blam]

I'm watching.

[P.O.E.]

So far, some well-done graphics, and the expected cliche characters. Looks worth watching.

[cripplecreek]

Don't worry, It would kill most of us in this country anyway. Michigans downwind.

[cripplecreek]

Nature has all kinds of nasty little suprises. Check out this link about lake Nyos in Africa. It will make you wonder about what lies at the bottom of our volcanic lakes in America.

http://www.geology.sdsu.edu/how_volcanoes_work/Nyos.html

[blam]

"Do we have a clue how many calderas there are in the world? This article cited Yellowstone and Sumatra. I believe the Bay of Naples in Italy is one. How many are there?"

I read somewhere the other day that most known supervolcano locations are in the United States.

[blam]

Here's a list of the supervolcanos.

[blam]

"Nature has all kinds of nasty little suprises. Check out this link about lake Nyos in Africa. It will make you wonder about what lies at the bottom of our volcanic lakes in America."

The Fremch have installed 'exhaust pipes' all the way to the bottom of these lakes and are now slowly exhausting off any accumulated gasses.

[cripplecreek]

I was checking the system out that pumps water from the bottom of the lake. I remember reading about the lake Nyos disaster when I was a teenager.

[Jim Noble]

The probability goes way up when it has been 760,000 years since the last one. Who knows that math?

I do, and you're wrong.

If you flip a coin 1000 times and it comes up heads every time, the probability of heads on the 1001st flip is 0.5.

[AaronInCarolina]

I do, and you're wrong.

If you flip a coin 1000 times and it comes up heads every time, the probability of heads on the 1001st flip is 0.5.

Jim, you are correct, theoretically. In an unchanging system for which a probability has been established (such as a coin that has not been weighted to favor one outcome versus the other) probability on any given event is always the same without regard to previous outcomes. However, in the scenario which you cited where a coin flip yielded heads every time for 1000 times, it is highly likely that the coin is not a "legal" coin (one which has a 1-in-2 chance of heads), and therefore the 1001st flip will highly likely yield another head. However, I know you were talking hypothetically about 1000 heads in a row with a legitimate coin (as unlikely as it is), and you are therefore quite correct about the 1001st flip chance of heads being 50% chance.

That being said, applying this analogy to a volcano, which presumably is an ever-changing system, in my opinion is incorrect. The article pointed out that the 1-in-740000 chance was a quite crude approximation based only upon the lapse of time since the last eruption. It is probably incorrect to apply such rigid standards (as one does to a legitimate coin) to a crude probability concerning a volcano. A volcano eruption is typically cyclic, and is therefore a constantly changing system whereby passage of time almost certainly increases the real probability of eruption, crude estimates not withstanding.

[Strategerist]

Glancing at the list it seems pretty flawed; Crater Lake's cataclysmic eruption was a VEI 7, not 8...I've never seen it classified as a supervolcano. The Australian volcano is very old and really can't be considered as potentially active. Some of the others listed were not VEI=8 eruptions either.