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.
David Rasmussen

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.

University of Utah professor Robert B. Smith at the Lake Butte seismograph.
Jim Peaco

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.

What are you studying now?

We’re working with geology that is “alive.” Calderas tend to breathethey rise and fall and rise and fall. And earthquakes are the heartbeat of this active volcanic system. With the seismic network in place, we’re keeping track of the earthquakes. We had one just this morning at 4 o’clocka magnitude 4. The newer technology that’s providing information is the GPS system, which we began installing in the mid-80’s. These stations measure the upward or downward movement of the ground, whether driven by earthquakes or by magma or hydrothermal fluids moving underground. Between 1923 and 1975 the entire Yellowstone caldera rose 1 meter. And suddenly in 1985 it reversed and started subsiding. Then in 1990 it started to go back up. Right now we’re studying an uplift surge that began about two years ago.

Can you share a moment when the volcano was particularly “alive”?

One day I was flying in a small plane with a National Geographic photographer--we were taking pictures of the caldera at an altitude. We had just turned back from the Norris Geyser Basin, low on fuel and out of film, when I saw clouds of haze below. I thought it was a forest fire, but it was Steamboat Geyser erupting. It’s the tallest geyser in the world, and it hadn’t erupted in five or ten years. I only had four pictures left in my camera, and used them all. What are the chances? The thing erupted for 10 to 20 minutes. We actually flew through the steam cloud that had risen a thousand feet into the air.

With such a history behind you, how do you see Yellowstone now when you arrive for work?

Whether you’re in the frontcountry or backcountry you’re always seeing something new at Yellowstone. Just over my career it has changed immensely. A huge earthquake occurred in my career. I’ve seen a caldera go up and down almost a meter. At Yellowstone, the changes are short term enough that you can observe them and see how they operate. Every time I go to Yellowstone I’m impressed and educated by new things. It’s always exciting. It’s just such a wonderful place.