The earthquake swarm beneath Yellowstone National Park seems to have subsided for now. At least that is what the public data from the Yellowstone Volcano Observatory are telling us about the supervolcano beneath the park. Now lots of my blog's readers have raised questions as to whether we are being told the truth by the U.S. Geological Survey. (This is my chat with the head scientist at the YVO, Jacob Lowenstern.) I have been in touch this weekend with experts from around the world. Here is some of what they are telling me. (More to come. And here is a nice, though dated, piece from the Financial TImes.) First up is volcanologist Dr. R.B. Trombley of the International Volcano Research Centre:
What does the earthquake swarm mean?
It is our opinion, and in agreement with Dr. Robert Smith of the University of Utah, that the current events are more of a major seismic event rather than a major volcanic event. The Alert Status of Yellowstone continues, at this time, to remain at the Green Alert Level. We do not anticipate the Alert Level to be raised at this time.
Given the current data, might the swarm be a prelude to a major seismic event ?
It could be but the swarming is too "isolated", i.e., it is near the lake area only basically.
What would be worrisome signs that that we might be headed to a major volcanic event ?
Much greater magnitude earthquakes, over a larger area of the caldera.The caldera is approx. 32 mi long by 8 miles wide. I believe the gratest quake so far has only been a 3.9 and all of the 'quakes so far have been from 1 to 10 km of depth.
I also talked to a top Hawaii-based volcanologist who was relucatant to go into specifics on the record since the scientist had only web data to go on, unlike the folks at the YVO. But I think these comments are pertinent:
Bob Smith, who is a seismologist and a great one, is a real straight shooter and is going to tell folks what he thinks, when he has enough information to think something. Ditto for Jake Lowenstern of the USGS. So I believe them when they say that they don't really know at this point what this swarm portends as Yellowstone is very seismically active. ... The odds of a big caldera forming eruption at Yellowstone are really infinitesimal during our lifetime. While the Discovery channel documentary did a fair job of portraying how an eruption might come down, it also did a better job of whipping up anxiety about a very unlikely event. You would be much more productive hiding in your closet avoiding lightning than worrying about a Yellowstone eruption. It's a wonderful thing to ponder and try to get a grip on some of the wild things that happen on our planet, but not something to stay awake about. The last rhyolite lava eruption was 80,000 years ago or so, that's 8 times as long as human civilization and represents roughly half the time modern humans have existed, just to put in perspective. Humans tend to be a bit egocentric thinking that all this stuff is happening to them personally, when it's just happening as part of nature. Anyway, Yellowstone while certainly doing stuff, is not in the same category of likely caldera eruption as Rabaul and Campi Flegrei. ... These quakes were much bigger than the Yellowstone swarm and many many more of them. And the final eruption from 2 volcanoes at the same time turned out to be relatively "small" though it buried the town in ash.