Yellowstone: Monitoring the Fire Below
Volcanic Witness: An Interview with Bob Smith
University of Utah professor Robert B. Smith has spent nearly his entire 40-year scientific career studying the volcanic setting of Yellowstone National Park and geologic evolution of the Teton Range. He directed and installed much of Yellowstone’s 23-station seismographic and 15-station Global Positioning System networks. We were curious how Smith’s ample experience as a geophysicist affects the way he sees majestic Yellowstone National Park.
Yellowstone National Park is a plateau in the Rocky Mountains. The mountains once at the park site were removed via volcanic eruption.
Can you describe Yellowstone National Park for one who has not yet seen it?
Right now, I’m in Jackson, Wyoming, looking up at the high mountain range of the Tetons. When you drive into Yellowstone, as I’ve done hundreds of times, you drive 50 kilometers up a long, flat plateau with maybe 300 meters of elevation gain to heavily forested terrain. But once you break out of the forest and you look for the mountains you’d expect in a Rocky Mountain setting, they're gone—they were destroyed during Yellowstone’s three gigantic volcanic eruptions 2, 1.3 and 0.6 million years ago. Some mountains were either blown away or subsumed back into the big magma chamber. The plateau is the product of that destruction. Later, many smaller, but still large volcanic eruptions flowed lava across the terrain, smoothing it out.
But Yellowstone has cliffs and hills. How did they get there?
In the last few thousand years frequent earthquakes have broken Yellowstone’s ground unevenly. You can’t see the faces of these faults well, as they are covered with timber, but you’d see one clearly if an earthquake occurred. The largest earthquake recently was the magnitude 7.5 just northwest of the park at Hebgen Lake, Montana, in 1959. It killed 28 people and made a fault 6 meters high and 60 kilometers long. Such earthquakes have helped break up Yellowstone’s topography, added hills and valleys, cracks and cliffs and escarpments. There are also a couple of places where the magma lifted the topography above magma chambers and created a dome: one at Old Faithful and another to the north called Sour Creek dome. These domes remain 500 meters higher than the surrounding plateau.
So without mountains in the way, is it easy to see all of Yellowstone’s geology?
Yellowstone is too big to see at once. It’s about 160 kilometers long from one end to the other. It’s not like you can just park your car and walk around the entire volcano like you can at Kilauea in Hawaii. Also, a lot of Yellowstone is still wilderness, and inaccessible. The things the average visitor sees are the geysers and valleys because that’s where they built the roads.
Have you explored in many of those inaccessible areas?
I’ve done a lot of work in the backcountry. I’ve installed earthquake seismographs, made studies of deformation using GPS, and mapped out some of the big fault escarpments that were not well understood. Some are 30 kilometers from the nearest road and only accessible by horseback.
