Video transcript
The video is 7 minutes and 15seconds long.
Produced by the American Museum of Natural History, June 2006.
Visual: Moose and bison wander among fields. A bird pecks at the ground. A waterfall crashes down in a valley. Tourists photograph a geyser.
Speaker: Henry Heasler, Park Geologist, Yellowstone National Park
What is special about Yellowstone is up to every individual to define.
Visual: Henry Heasler, Park Geologist, Yellowstone National Park, in Yellowstone Park
It can be everything from the beautiful clear skies at night, to watching wolves, to just enjoying being out in nature.
Visual: A grassy plain. A bison in a field by the roadside. Other bison wander on the road, while tourists in a car slow down and photograph them.
From a geologist’s standpoint, the volcano is what makes Yellowstone Yellowstone.
Visual: Geysers erupt. Mud boils. Gas and mist escape from fissures and cracks in the ground. Hot springs bubble.
Title: Yellowstone: Monitoring the Fire Below
Visual: Jacob Lowenstern, Geologist, United States Geological Survey, in Yellowstone Park
Speaker: Jacob Lowenstern, Geologist, United States Geological Survey
There are different definitions of what an active volcano is. And to the public, an active volcano is one that’s erupting. Now. 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, and there’s been an eruption.
Visual: Gas and mist escape from the ground at various locations at Yellowstone.
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.
Visual: Animated diagram of cross section of the Earth.
And there is a hot spot that’s down there, where rocks are being melted. This region of 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.
Visual: Jacob Lowenstern in Yellowstone Park
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 for example, the one that occurred 640,000 years ago is on the order of 1,000 times more material than was erupted at Mount Saint Helens’s eruption in 1980.
Visual: Jacob Lowenstern and another geologist carry geologic monitoring equipment to a hot spring. Gas and steam form a column out of the ground at various locations in Yellowstone.
Scientists have become quite successful at predicting, on a short-term level, whether a volcano’s going to erupt or not.
Visual: Gas and steam rise out of the ground in various locations at Yellowstone.
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.
Visual: A scientist attends to equipment, collecting escaping gases from the ground.
You might also expect some sort of a thermal anomaly, where we see increased gas flux or increased heat flux in an area.
Visual: Jacob Lowenstern at Black Pit. A scientist operates monitoring apparatus in the background.
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.
Visual: A scientist extends a long metal tube into the pit of gas and steam.
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.
Visual: A scientist holds a bottle into which the gases are collected.
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.
Visual: Jacob Lowenstern writes in a notepad.
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.
Visual: Jacob Lowenstern feeds a sensor into a pit of rising gases and monitors an electronic device.
And so our job is to make sure if that’s going to happen we know what’s going on.
Visual: A bubbling hot spring.
Speaker: Lisa Morgan, Geologist, United States Geological Survey
Volcanoes aren’t the only things that are happening in Yellowstone.
Visual: Lisa Morgan in front of a lake.
In fact, large hydrothermal explosions are much more frequent and pose much more of an immediate hazard, a local hazard, than the volcanic activity does.
Visual: Animated diagram of a cross section of Earth
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.
Visual: Gas and steam rise out of the ground at various locations at Yellowstone
But it’s contributing the heat that we see in Yellowstone in warming the water that causes the hydrothermal features that we see such as the fumaroles, the hot springs, the geysers.
Visual: A large group of tourists sit on benches, watching a geyser. Gas and steam rise out of the ground at various locations at Yellowstone
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. And so you have all of a sudden this explosion of material—mostly hot mud, water, and rock fragments.
Visual: Tourists gather on a walkway to observe steam rising out of the ground.
Over the last 14,000 years, we estimate there’s somewhere between 20 to 25 large hundred-meter-in-diameter hydrothermal explosions in Yellowstone National Park.
Visual: Northern Yellowstone Lake at Mary Bay. Two researchers walk along its shore.
We’re on the shores of Northern Yellowstone Lake at Mary Bay.
Visual: Lisa Morgan standing on the rocky shore of the lake.
The Mary Bay explosion event was the largest, or is the largest documented, hydrothermal explosion in the world. Its crater diameter’s about 2.6 kilometers, and it extends all the way over to those green grassy cliffs or bluffs across the lake.
Visual: Light green grassy bluffs at the other end of the lake’s shore.
This lake now occupies the explosion crater and is just one very good reminder that hydrothermal explosions are a very real hazard and one that happens much more frequently than volcanic activity does in Yellowstone.
Visual: Lisa Morgan and another researcher walk along the shore of the lake.
Speaker: Jacob Lowenstern
Visual: Cliffs and valleys, and lakes and streams at Yellowstone
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.
Visual: Tourists walk along a man-made wooden walkway along boiling mud flats.
It’s an extremely unlikely thing to happen. Again, it’s only happened several times here over two million years. But it’s something that people have to be aware of.
Visual: Rocky cliffs
Speaker: Lisa Morgan
I’m not so concerned. I think these are natural processes, and this is how the Earth is formed.
Visual: Lisa Morgan examines a large rock sample. Rocky cliffs.
These are the largest volcanoes on Earth, and they’ve really shaped our landscape in a dramatic way.
Visual: Grassy fields.