don't know. These things (lava flows and bursts) go up and down and then burp," said Robert B. Smith, professor of geology and geophysics at the University of Utah.

Smith, a Yellowstone volcanic region expert and USU alumnus, spoke about the statistics that led to the study of a potential volcanic eruption, on Friday afternoon in the Taggart Student Center Auditorium.

During the lecture he showed slides of the different parts of the seismic

volcano.

He said Yellowstone itself sits atop a plume of magma under the earth's crust and that magma comes up and produces another crust, a "crustal magma chamber," and then that erupts to the surface to create geysers or hypothermal systems.

One big change to the landscape has been the rising of valleys and the sinking of mountains.

In 1973 on the south end of Yellowstone Lake, a submerged boat dock at Peale Island was discovered.

It's the caldera, a crater formed by a volcano eruption, in the center that's causing the uplift, Smith said. From 1991 to 1995, the caldera was going down, but the trend went up from 1995 to 2000, and now from 2004 to 2006, it is "really going up," he said.

"When you pump up a balloon, it rises vertically and expands laterally," he said. That's what the magma plume is doing under the surface of the earth.

He said that geysers in Yellowstone need the volcano to survive. And the earthquakes also help with that. Yellowstone records 1,000 to 3,000 earthquakes per year.

"It's all linked together. Yellowstone is based on a plume," Smith said. "The plume is fixed in space and the plate is moving southwest."

He showed an example of this motion with a bottle of molasses and a table.

The plume, an upwelling of magma, would be the molasses being poured onto a table, and if someone moved the table, then the molasses would spread out over the table.

"But in the case of the plume, it would be flowing upwards instead of down onto a table," Smith added.

"We just calculate statistical probability, the likelihood using aging statistics. It's mathematical. We take the ages, and they repeat the average frequency of the events and then calculate when the last event occurred, and what's the probability of exceeding the threshold of an eruption, or an earthquake or a fault." Smith said.

Compared to earth's history, Yellowstone is very young, he said.

"Only two million years out of a four-and-a-half billion history of the earth," Smith said. "So in human time, I say it was only the last five seconds."

Smith has studied Yellowstone for more than 40 years and directs the park's seismic and GPS network.

With that project, he helps monitor the temperature of the ground on the boardwalks around the geysers and the probability of a large earthquake occurring.

One large earthquake was the Hebgen Lake earthquake in 1959 in Montana, which had a magnitude 7.5.

"It's the biggest earthquake in the interior of the U.S. not including the San Andreas. The San Andreas has larger earthquakes and a lot more deaths, of course," he said.

He said the lake water is generally cold, but the temperature increases from the hot springs and can bring the Yellowstone water temperature up to a little more than 100 degrees.

His studies showed that the first Yellowstone eruption, more than 21 million years ago, spanned across 600 cubic miles. That range included about 18 states around the south, east and west.

Yellowstone's measured caldera today covers all of the national park and into Idaho and Montana.

The oldest lava flows are in the center of the caldera and spread out to younger ones from there. The youngest lava flow was the 70,000-year-old Ritchstone Plateau flow, which formed the Beachler Meadows.

The studies he presented this past week are part of a paper he is compiling which he plans to have done by April.

To see the pictures and some of the videos he presented, go to www.yellowstonegis.utah.edu.