There was a very large earthquake swarm at Yellowstone National Park a few weeks ago which caused some concern in certain quarters. In following discussions of the subject, I noticed that it was widely assumed that a super-eruption at Yellowstone would be an extinction-level event on par with the asteroid strike in the Yucatan 65 million years ago that (possibly along with volcanic activity in India) extincted the dinoraurs.
This clearly seems erroneous - we have super-eruptions on earth about every 100,000 years, and I never recall hearing about one of them causing this or that species to go extinct. The only exceptions are the vanishingly rare “mantle plume” eruptions like the aforementioned one that formed the Deccan Traps in India around the time the dinosaurs went extinct and the Siberian traps in Russia 250 million years ago that likely caused the greatest mass extinction ever.
I don’t doubt that a super-eruption would be an unprecedented calamity, but it seems to me that the absence of a clear fossil record showing extinctions accompanying the regular (i.e. non-mantle plume) super-eruptions suggests that the effects of a super-eruption may be overstated. Anyone disagree and is there any indication that super-eruptions, like the Toba eruption in Indonesia actually caused species to go extinct?
From memory I think supervolcano was linked to the Permian mass extinction…and on the Discovery Channel they had a show that was talking about alternative theories to the extinction of the Dinos during the end of the Cretaceous (?) as being in part caused by a super volcano eruption.
The short answer though is that scientists just don’t know what all the factors were that caused a lot of the mass extinctions in the past. My guess though is that many of them were multiple events…disease, climate shift then bam! Super volcano! Or super volcano, climate shift then bam! Big rock falling from the sky!
Thanks for the welcome. I’m aware of the Toba theory, and I don’t doubt that Toba would have caused a lot of starvation among hunter-gatherering humans. But if super-eruptions were all THAT horrific, I don’t think we’d have to talk about mere bottlenecks- we’d be able to point to a large number of actual extinctions, especially among herbivore species like giraffes and gazelles. The absence of such extinctions leads me to strongly suspect that plant life survives even the largest, VEI level 8, eruptions.
Correct, but those are the “mantle plume” eruptions I was talking about. They are fundamentally different from the Toba/Yellowstone type supervolcanos- and are far larger. Basically, a mantle plume eruption involves an enormous blob of magma rising from the earth’s mantle and then erupting as flowing lava in many volcanoes over a huge surface of the earth. A huge part of the surface of Siberia and India are the rock from those eruptions.
The Toba event coincides with the Genetic Bottleneck which indicates a very low level of population and a subsequent lack of genetic diversity. There is evidence to suggest we were nearly wiped out.
But even if WE were almost wiped out (and there is still controversy about what caused that bottleneck), I don’t think Toba caused a mass extinction across the board…at least not that I have ever heard about.
It wouldn’t be on the same level as the K-T event. It would possibly be on the same level as a 1 kilometer asteroid hitting the Earth. The K-T impactor was more like 10 kilometers. A 1 kilometer asteroid impact is thought to be roughly the smallest impact that would cause global effects, rather than just local destruction and tsunamis.
One supervolcano could still ruin your whole day, though.
It would very likely collapse the US economy, with heavy ashfall ruining agriculture in the much of the west and midwest for centuries. The Western states that rely on the Colorado River and Hoover dam for water and electric power would be out of luck- they would be clogged with ashflow. I’m not sure how places like Las Vegas could survive that.
So I agree it would be unimaginably catastrophic, which is why I was nervously checking the Yellowstone seismograms in early January. Here’s what they look like today, nice and calm: http://www.quake.utah.edu/helicorder/yft_webi.htm
In early January, these same seismograms were filled with hundreds of earthquakes- the most worrisome earthquake swarm in Yellowstone’s history. There was a slightly bigger one in 1988, but it was in an area outside the actual caldera, so it was less worrisome than the one we just had.
It could happen any time between now and a few hundred thousand years from now. It’s not a matter of if but when. And when it does happen (well, when the big one happens…we may get some small ones over the course of the next few thousand years or so) it will probably destroy the US (happy days for our Euro buddies! Woohoo!).
I wouldn’t hold my breath though. From what I’ve read it’s not looking like it’s going to happen in our lifetimes (you never know though). I do recall that one of the OTHER super volcano’s out there (I don’t remember which one) looks like it might be closer to the explosive point. From memory Yellowstone is something like between now and a few hundred thousand years for the next big one, but this other one is between now and a few thousand years.
Or I could just be mis-remembering. That happens fairly often.
No, Yellowstone is by far the most dangerous current supervolcano. I think it’s the Long Valley caldera you’re thinking about- it may have a smaller eruption but is hundreds of thousands of years from a supereruption.
From what I’ve read, if you’re in an area of deep ashfall then you can’t grow crops there because the ash is too acidic and, in addition, the ashfall blocks oxygen from reaching the soil and kills all the little microorganisms that make the soil fertile. You’re just left with dead sterile dirt which can take a very long time to recover. If the ashfall is lighter then things may be fine- it all depends on the depth and whether oxygen can reach the soil.
Don’t forget that volcanic ash is very bad for your lungs. It’s very abrasive, and when it gets into the lungs it combines with moisture and becomes something like cement. I’ve heard it also tears up plane and car/truck engines. About 4 inches of volcanic ash is enough to collapse a lot of roofs.
At least until the price of food skyrockets, once the US and Canada aren’t exporting any more. Kind of like what happened when the price of food went up last year, only a lot worse and probably not confined to the Third World.
Well, I was pretty much talking tongue in cheek there. They don’t REALLY want us destroyed…just humbled a bit and perhaps back under their thumb where we belong.
But yeah…if Yellowstone goes it would be bad days for the world. The US would essentially cease to exist as a coherent nation and the rest of the world wouldn’t be too much better off than we would be. There would be some fairly severe climate change, lots of crop failures and disease. Would be pretty grim.
It depends on the depth. Here is all the info you might want on the subject along with the money quote:
Ash falls greater than 10-15 cm (4-6 in) typically result in the complete burial of pastures and soil. Where soil burial is complete, the soil will become sterile because it is deprived of oxygen; existing pasture species and crops and most soil micro-organisms will die. Where ash is as thick as about 5 cm (2 in), plant survival and re-growth will be dependent on several factors, including the chemical nature of the ash, compaction of the ash after the eruption, degree of continuing disturbance, amount and reliability of rainfall, and length of plant stalks at the time of ash fall.
Long term, deep volcanic ash will turn into highly fertile soil- see Idaho- but it’s a very long process, the length depending largely upon how acidic the ash is.
