The bags and maps are packed, the cameras are loaded and Robert Smith is ready for another trip to Yellowstone National Park.

This time, the geophysicist who has spent most of his life studying one of the largest sleeping volcanoes in the world has an ulterior reason for heading north. "I suppose there is a sense of urgency," he says, laughing. "My lawn needs to be mowed."

Robert, who lives in Holladay and teaches at the University of Utah, owns a second home outside one of the prettiest spots on the planet, but he didn't buy the place just for the view.

Having an address near Yellowstone gives him another excuse to get away from the city and monitor the movement of the enormous volcano boiling beneath the national park. Although the chances are remote that the volcano will erupt in his lifetime, "if it happens, I'd love to see it," says Robert, 58, who has studied the active hot spot for almost 40 years.

"From a safe distance, of course."

Robert made headlines in 1979, when he and a study team discovered that the Yellowstone caldera was a living force that was building upward, inch by inch. The last major eruption of the supervolcano was about 640,000 years ago, he says, with smaller eruptions occurring about every 20,000 years.

Eyebrows go up when Robert talks about the last time a "small" eruption happened 70,000 years ago. Although most of us assume that means the average eruption is 50,000 years overdue, Robert says we can relax. "These things take lifetimes to happen," he says. If he had a nickel for every time somebody has asked him, "When will it blow again?" he could retire tomorrow.

Now that thousands of summer tourists are descending upon one of the world's few supervolcano sites, it was a good time to catch up with the professor over a Free Lunch chat during a break in packing for his latest trip.

Born and raised in the Cache Valley, with summers spent playing beneath the Tetons in Jackson, Wyo., Robert grew up with an appreciation of the West's rugged landscape. But it wasn't until after the Hebgen Lake earthquake of August 1959 that he developed an intense fascination with how the Yellowstone area was formed. The magnitude 7.5 quake killed 28 people and triggered a massive rock avalanche.

Surveying the damage as a geology student at Utah State University, Robert knew that he wanted a career studying the rumblings in his own back yard. In 1983, he set up seismometers around Yellowstone and discovered there were about 2,500 small quakes every year in the park.

Ultimately, he was able to link the shaking to the volcano heaving deeply below the surface. Today, he monitors the caldera from the computerized Yellowstone Volcano Observatory that he helped establish.

"It sure beats the old way of keeping track with paper records," he says.

Although it is inevitable that a large eruption will one day occur, coating most of the country in volcanic ash, Robert isn't worried about it happening on his watch. Volcanic time is measured in millenniums, not days. And at this particular moment, the professor's biggest concern is the hour.

Now that lunch is over, it's time to hit the road. If he's lucky, the lawn will be mowed by 8, giving him time to enjoy another spectacular sunset in Yellowstone Park.

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