Quake disrupted park's geysers

A strong earthquake in Alaska temporarily caused geysers to become not so faithful in Yellowstone National Park, says a study by a University of Utah and Yellowstone experts.

Yellowstone is a gigantic volcano caldera with a geyser system covering many square miles. Heat from underground magma powers the hot springs, steam vents and 10,000 geysers.

This is "the first time, as far as we know, that there's been such a profound change in the geysers from the passage of the earthquake waves," said a co-author of the study report, U. seismologist and geophysics professor Robert B. Smith.

The report was carried in the June edition of Geology, the journal of the Geological Society of America. Authors of "Changes in Geyser Eruption Behavior and Remotely Triggered Seismicity in Yellowstone National Park . . . " are Smith; Stephan Husen, a U. adjunct assistant professor of geophysics now at the Swiss Seismological Service, and Ralph Taylor and Henry Heasler, both at Yellowstone.

When the 7.9-magnitude earthquake shook the Denali, Alaska, fault in November 2002, its seismic waves triggered small earthquakes and other evidence such as motion in swimming pools as far away as Louisiana. That was reported at the time of the quake, whose effects also were observed in Salt Lake City.

What's new is that the study says the Denali event induced changes in the frequency of several geysers. The report says several small hot springs at Yellowstone suddenly came to a heavy boil, and one hot spring that is normally clear turned turbid.

The team studied eruptions of 22 geysers, finding that eight showed changes in the eruption intervals. (Old Faithful was not one, remaining as predictable as its name implies.)

Some geysers erupted less often than normal, some were unchanged, some became erratic, while others spouted off more frequently. Several changed remarkably, Smith said.

"They put out a lot more fluid . . . before they came back to normal." Return to normal patterns took a matter of days to three months or so.

The geysers did not become turbid because of the changes. "That's the surprising thing," Smith said, because the underground plumbing changed when the seismic waves jolted through.

Digital loggers kept track of the geysers' activity, he said. "My co-authors had to go back and retrieve those data," skiing into the area.