University of Utah geologist Dr. Robert Smith updates on whether Yellowstone is about to blow or not.
HH: You’ll want to listen to this, because it’s really fascinating. If you caught yesterday’s program, I was reading to you from Bill Bryson’s A Short History of Nearly Everything, about the Earth, and it’s capriciousness, and my discovery, to my amazement, that Yellowstone National Park is not just a wonder on the top, it’s a wonder below the surface. Joining me now to go through that is Dr. Robert Smith of the University of Utah. He’s also director, I believe, of the Yellowstone Teton Project. Dr. Smith, welcome, good to have you.
RS: Hi, how are you?
HH: Good. Tell us what your job is at Yellowstone.
RS: Well, I’ve been working at Yellowstone for about forty years as a researcher interested in working on earthquakes and the volcanic history of Yellowstone. And currently, I’m a member of the Yellowstone Volcano Observatory, which is a partnership between the U.S. Geological Survey and Yellowstone National Park, and me at the University of Utah. And our component is to operate the seismograph network in Yellowstone, and to operate the GPS, global positioning monitoring system network for measuring ground deformation. So my role is both in the role of monitoring for public safety, and being a scientist, I’ve studied the Yellowstone system for many, many years, in terms of its evolution, and it’s structure, and the capability for large earthquakes and volcanic events.
HH: When was the last big volcanic bang, Dr. Smith?
RS: Well now, let me explain a little bit about the history. Yellowstone has had the now well known supereruption, if you wish. There were three giant eruptions, which have caught on as the supereruptions. The first was two million years ago, and then one at 1.2 million years ago, and the latest, 640,000 years ago. And these are giant eruptions that have never really been witnessed or documented in historic time, and these are eruptions that exploded, caused a collapse of a caldera, the ground floor of this volcano at Yellowstone, which was forty, fifty miles wide. You compare it to the caldera you see in Hawaii, these are thousands of times larger. At any rate, the last supereruption was 640,000 years ago. But since then, there’s been about 30 smaller eruptions, like the size roughly the scale of the 1980 Mount St. Helens’ eruption. And the youngest of those is 70,000 years. But since then, there’s been, of course, a lot of smaller…there’s been earthquakes, large earthquakes, in fact, some of the largest in the history of the Rocky Mountains have occurred in and around Yellowstone. And there are hydrothermal eruptions, which are eruptions of hot steam that come out of the geysers and the fumaroles. And they produce little craters, maybe a kilometer, a quarter of a mile in dimension at its largest size. So we go on a scale from big ones that happen very rarely to smaller ones that happen more frequently.
HH: Now what is the probability of another big one?
RS: Well, we don’t know. Remember, we’ve only had three big ones, and so people say well, the last one was 640,000 years ago, and for some reason, sitting out in the public perception is that these things erupt every 640,000 years, where in fact, between the three big eruptions, the time, repeat time is about 740,000 years.
HH: So we’ve got 100,000 years?
RS: Well, that’s if you believe it’s going to happen. The problem is that we only have two times, and any mathematician will tell you, or anyone averaging their checkbook, if you only have two transactions, that’s not a good number to determine a long term average. So we’re not prepared to say that that’s a long term number we can use.
HH: So we can camp there this summer?
RS: Well, I certainly am.
HH: All right. Well, it depends on how old you are, the amount of data I’ve put into that, Dr. You might just be throwing caution to the wind. Let me ask you, what have you seen recently in the seismic activity in terms of the calderas rising and falling?
RS: Well, there’s two things happening. Number one, Yellowstone’s been a very seismically active area since it was first discovered in the 1870’s. And our monitoring systems suggest we get on the order of a thousand earthquakes a year, you know, year in and year out. In the last few years, in fact, that number has been decreasing. So on the other hand, from this new technology provided by global positioning systems, where the ones we use, not the backpackers version, but the ones we use, we can measure down to a few millimeters of changed in height. And we’ve discovered in the last few years that the caldera has been rising at roughly, oh, three to four, up to six centimeters per year, which is two or three times, four times the rate that it had been rising in the past two decades. So the caldera’s been going up while the earthquakes have been decreasing.
HH: And so what’s that tell you? Anything?
RS: (laughing) It tells us a big scientific question. And we don’t really know what that means. We think it’s probably…we know there’s a magma chamber beneath Yellowstone at a depth of about five miles, and a magma chamber is not this big volume that people commonly think that’s 100% melt, that you can row a boat around in. It’s a rock that’s very porous, like a sponge. And you can think of a rock containing a lot of pore spaces, and in the case of these magma chambers, 10-20% of the pore spaces have magma, I mean, molten rock. That’s down about five miles. And what we may be seeing in this latest deformation, uplift of the caldera, is we’re putting magma into those pore spaces. It doesn’t mean there’s an imminent threat of a volcanic eruption, but it’s certainly telling that the process is very active, and it’s very much alive.
HH: Is it possible that we would have a super volcano eruption?
RS: Well, you can’t say that it’s not possible, but we don’t have any indications that it would be.
HH: So what would it look like? If you had a blow along the lines of the one 640,000 years ago?
RS: Yeah, if it was something that large, we would expect to see a large area of the whole Yellowstone plateau, the whole Yellowstone region, start to have earthquakes occurring over…you know, Yellowstone’s 80 miles long and 80 miles wide. We would expect to see earthquakes occurring over an area of the whole caldera, and that would be, it would cover a very, very large geographic area. We would expect to see the ground beginning to deform over that whole area at high rates. We would probably expect to see changes in the chemistry of the gases that were coming out of the hot springs and the geysers. We would expect to see maybe even a temperature change. But we…and we monitor the ground motion with GPS, we monitor the earthquakes. And so because we’ve never observed one, you know, in historic times, in terms of understanding them, we don’t know what to look for precisely, but we can scale up other volcanic eruptions.
HH: I’m talking with Dr. Robert Smith of the University of Utah. He’s one of the majordomos in Yellowstone, following on my conversation with you yesterday, America, about Yellowstone. So Doc, if it did go, if we had the big one, what would the day after look like?
RS: (laughing) Well, we would be covered by a lot of ash.
HH: How far? Not me, I’m in California. Maybe you.
RS: Well, I have a home up in that country, and I’d be…we think we’d get thirty to forty feet of…well, first of all, you’d have, if you had a giant eruption, the scenario that’s been predicated upon our observations is that you would have an eruption of ash and material into the atmosphere that could go as high as 60-80,000 feet, would get caught in the jet stream, and these ashes are very light. In the past eruptions, the ashes were spread out over the Western United States. It could be as deep as 20 to 30 feet over Yellowstone itself. It could be up to a foot at distances of just two to three hundred miles, like Salt Lake City. And so it could cover a large area, and this would probably occur over a period of days, because this material has to rain down over time. It doesn’t happen instantly.
HH: So what would that do to our quality of life?
RS: It would really change it.
HH: (laughing) Would it cool the Earth?
RS: Well, I mean, certainly, if you put this insulating layer, a layer that would reflect the light back into the atmosphere, then there’s been hypotheses that it would produce a volcanic winter equivalent, and I’m sure it would change. And we think a lot of the prehistoric changes in climate, in fact, have come from large volcanic eruptions, and depending on the amount of sulfur that gets into the atmosphere, which is the main agent that causes the reflection of the sunlight, it could certainly produce that effect.
HH: It would shut us down pretty well. Let me ask you, Dr. Smith, if you had to guess where the next major seismic event, either earthquake or volcano was going to come in the Continental United States, would it be Yellowstone? By major, I mean a 7.7, or at least a Mount St. Helens volcano blow.
RS: Well, you’re talking about two different mechanisms.
HH: Yes, I am.
RS: Of course, we look at the frequency of large earthquakes. And the state that has the biggest earthquakes, and the most frequent ones is Alaska, in the Aleutian chain. And it also has the largest frequency, or the largest number of active volcanoes. That’s where it would probably be, either one of those events.
HH: How about down here, in the lower 48?
RS: In the lower 48? Well, the San Andreas Fault, of course, ruptures every hundred and fifty years.
HH: How about volcano, though?
RS: Well, that’s hard to say. The Cascades are probably the most likely place, because the Cascades system, Washington and Oregon, have many more. There’s over a dozen of these high strata volcanoes, and we, that would probably be the next most likely. Now remember, Mount St. Helens was tiny. It’s thousandths of a size of a Yellowstone eruption. So Yellowstone, and what we call the Long Valley caldera in Eastern California, Mammoth Lakes ski resort area, these are two large calderas. They erupt very, very less frequently. They’re just much bigger when they do.
HH: Is the Long Valley overdue?
RS: Well, the last one was 740,000 years ago, but there was never one before it, so we don’t know if there is a time we would expect the next one. But it certainly has activity much like Yellowstone. It has uplift deformation, it has earthquakes, and it’s being monitored for the same reason.
HH: Dr. Robert Smith, fascinating. I’ve linked to your website, as well as the Yellowstone Teton Project’s website. Thanks for spending some time with us today. 740,000 for the Long Valley, huh? 640,000 for Yellowstone. Think I’m going to stay in Maine.
End of interview.