Yellowstone—Monitoring the Fire Below

[elk noise] [harmonica] What is special about Yellowstone is up to every individual to define. It can be everything from the beautiful clear skies of night to, uh, watching wolves, to, uh, just enjoying being out in nature. [harmonica music] From a geologist standpoint... the volcano is what makes Yellowstone Yellowstone. [harmonica music] [running water] There are different definitions of what an active volcano is. And to the public, an active volcano is one that's erupting. Now. Uh, to a geologist, there are a couple of different definitions, and one of them is simply that it's been active in the last 10,000 years. That there's been an eruption. Um, at Yellowstone, there hasn't been an eruption of magma in the last 10,000 years. But we see so many other indications that show that the system is alive, it's breathing. And there's fire below that could again come to the surface in the future. To understand the story of what's going on at Yellowstone, you have to look down in the mantle of the Earth. [background music] And there is a hot spot that’s down there where rocks are being melted. This region is melting, you can think of sort of as a blowtorch and it's melting the Earth's crust. And when that crust melts, it creates magma chambers high up in the Earth. Such as the magma chamber that's sitting beneath us at Yellowstone. And when that erupts, we get large volcanic activity. [background music] Some of the eruptions that have occurred at Yellowstone are among the largest volcanic eruptions that have ever been recorded on Earth. Recorded in the geologic record, that is. And, uh, for example, the one that occurred 640,000 years ago, is on the order of 1000 times more material than was erupted at Mt St Helen's eruption in 1980. Scientists have become quite successful at predicting on a short-term level whether a volcano's going to erupt or not. The most likely things that we'll see is some significant ground deformation, where the ground is moving significantly upward. We'd also combine that with seismic activity. Earthquakes. You might also expect some sort of a thermal anomaly where we see increased gas flux or increased heat flux in an area. This is a pool called Black Pit. And it's in the Norris Geyser Basin. And we are sampling the gases and steam that are coming out of this feature. We know that magmas are down there, they're putting off a lot of gas. So our goal as geochemists is to collect the gases and try to sort out what's happening one, two, three miles below us. And so we can look at the ratios of different gas species. Say, carbon monoxide to carbon dioxide, hydrogen to hydrogen sulfide, and we can try to unravel the temperatures and the pressures beneath us. I don't think that anything is due for us in the near future. I don't think that's very likely. I do think that Yellowstone is an active system, and it can have eruptions in the future. And so our job is to make sure that we are prepared, and that we know what's going on. Volcanos aren't the only thing that are happening in Yellowstone. In fact, large hydrothermal explosions are much more frequent and pose much more of a immediate hazard, a local hazard, than the volcanic activity does. The original magma chamber is still at depth beneath Yellowstone. And it's a huge mass that's still hot, and trying to cool and crystallize. So that big hot body is still there. But it's contributing the heat that we see in Yellowstone and warming the water that causes the hydrothermal features that we see. Such, as the fumaroles, the hot springs, the geysers. [harmonica] [banjo background] A hydrothermal explosion is basically a hot water event. And at some point in time, something triggers the water in the hydrothermal system to now flash into steam. [banjo background] And so you have all of a sudden this explosion of material mostly hot mud, water, and rock fragments. Over the last 14,000 years, we estimate there are somewhere between 20 to 25 large, 100 meter in diameter, hydrothermal explosions in Yellowstone National Park. We're on the shores of Northern Yellowstone Lake at Mary Bay. The Mary Bay explosion event was the largest, or is the largest documented, hydrothermal explosion in the world. It's crater diameter is about 2.6 kilometers. And it extends all the way over to those green grassy cliffs, or bluffs, across the lake. This lake now occupies the explosion crater, and it's just one very good reminder that hydrothermal explosions are a very real hazard from when that happens much more frequently than volcanic activity does in Yellowstone. [harmonica] If we did have the kind of eruption that has occurred, at Yellowstone in the past, it would be a major national event. There would be ash distributed over many of the nearby states. It would probably get as far as the Mississippi river in some cases. It's an extremely unlikely thing to happen. Again, it's only happened several times here over 2 million years. But it's something that people have to be aware of. [harmonica] I'm not so concerned. I think these are natural processes and this is how the Earth is formed. [harmonica] These are the largest volcanos on Earth. [harmonica] And they really shaped our landscape in a dramatic way. [harmonica]