Geyser bashing: distant quake alters timing of eruptions.

A powerful earthquake that struck central Alaska on Nov. 3, 2002, did more than just shake up the locals: It changed the eruption schedule of some geysers in Wyoming's Yellowstone National Park, more than 3,100 kilometers away.

Yellowstone, one of the most active hydrothermal regions on Earth, contains more than 10,000 geysers, hot springs, and steaming volcanic vents. As seismic waves from the Alaskan quake rolled through the park, several small, normally calm hot springs suddenly surged into a heavy boil, with some eruptions reaching heights of 1 meter or more, says Robert B. Smith of the University of Utah in Salt Lake City. Another hot spring nearby, which normally discharges clear water, suddenly turned muddy.

Scientists and park rangers also noted big changes in the eruption frequencies of 8 of the 22 Yellowstone geysers that are constantly monitored with instruments. For a few weeks after the quake, Daisy Geyser blew its top more often than normal. Lone Pine Geyser, on the other hand, erupted less frequently during the same period. The researchers suggest that seismic vibrations may have shaken loose some of the mineral deposits that normally constrict the geysers' subterranean plumbing, thereby changing their flow rates.

In contrast, Old Faithful, possibly the world's most renowned geyser, wasn't affected by the remote temblor. Smith and his colleagues report their findings in the June Geology.

In the past, large quakes near Yellowstone have influenced the eruption frequencies of some of the park's geysers. The influence of the Alaskan quake on Yellowstone's geysers is "the most distant triggering [of changes in hydrothermal activity] that I'm aware of, says Robert L. Christiansen of the U.S. Geological Survey in Menlo Park, Calif.

In the first 6 hours after seismic waves from the magnitude-7.9 Alaskan temblor passed through Yellowstone, clusters of quakes of magnitude 2 or smaller occurred around several of the park's major hydrothermal systems. Although Yellowstone has experienced clusters of quakes before, the November 2002 tremors mark the first time that multiple clusters have been observed there simultaneously.

In just 1 week, more than 1,000 quakes hit the park. It's not clear whether the local tremors triggered the changes in hydrothermal activity or vice versa, says Smith.

The study by Smith's group suggests that even small seismic triggers can have significant effects, Christiansen notes.