If a barefooted hippity-hop across a scorching-hot parking lot sounds painful, imagine walking a trail through the Norris Geyser Basin in Yellowstone National Park, where the ground temperature is a toasty 200-degrees Fahrenheit - hot enough to boil water.

"The trail is still hot and the trail is still closed," said park geologist Hank Heasler.

Effective July 23, most of the western portion of the Back Basin trail is closed due to increased thermal activity, starting at the Norris Museum. There are approximately 12,500 feet of trails in the Norris Geyser Basin with approximately 5,800 feet of trail affected by the temporary closure.

Norris is the hottest and most seismically active geyser basin in the park, according to the Yellowstone Volcano Observatory, a cooperative venture by the U.S. Geological Survey and the University of Utah. Recent activity in the Norris Geyser Basin has included formation of new mud pots, an eruption of Porkchop Geyser (dormant since 1989), the draining of several geysers, and the changing of several geysers' eruption intervals.

Scientists like Heasler have responded to the increased thermal action with a flurry of different equipment, gathering new data streams throughout the basin.

Heasler said it was a new opportunity to learn about the vast forces underneath Yellowstone National Park.

Fellow scientists are watching closely to see whether this increased thermal activity is accompanied by surface deformation, geochemical changes in hot water and steam, or shallow earthquakes.

Still to come is installation of delicate seismic or global positioning system (GPS) gear for additional measurements, he said.

Ground deformation has been detected by satellite radar interferometry research by Chuck Wick in Menlo Park, Calif., as well as by seismic research by University of Utah's Bob Smith. Activity in and around the Norris Basin has been picking up, Heasler said, including a new 750-meter line of fumeroles - holes which give off hot gases.

At its most pragmatic level, the closure of the Back Basin trail is all about safety for visitors and staff alike, Heasler said. In addition to hot ground, a new mud-pot has appeared which splatters hot, corrosive mud on the trail, he said. "You wouldn't want to get splashed with it," he said.

In a real sense, the scientists studying Norris and the other geothermal features of Yellowstone are like detectives, he said. "We gather evidence or data and try to find answers through the power of observation and deduction," Heasler said.

All the ongoing research is like writing a hundred different detective novels, then stepping back to find the big picture, he said.

In the past 2.1 million years, Yellowstone has produced three very large caldera-producing explosions - the last 640,000 years ago.

The three caldera-forming eruptions, respectively, were about 2,500, 280, and 1,000 times larger than the May 18, 1980, eruption of Mount St. Helens in Washington State.

The intensified research at Norris is a wonderful opportunity to gather baseline data.

"Is this like a little hiccup or is it like a big burp?" he asked. Only time and further research will tell.