A recent swarm of earthquakes may mean the largest volcano in the continental 48 states is reawakening about 25 miles south of this small town on the California-Oregon state line.
But geologists say more than 300 quakes recorded since mid-September may also be nothing more than a shifting of the mile-thick layers of rock left over from past eruptions by the Medicine Lake volcano, last active about 850 years ago."The odds are against its being an immediate threat," says geophysicist John R. Evans of the U.S. Geological Survey. "But we're not sure. You have to see a volcano do all its tricks before you can predict it reliably."
Adds geologist Stephen Walter, "We think there could be potential danger. We're still getting a handful of earthquakes there every week and we don't have a great deal of history to look back on."
But no one who lives near Medicine Lake is panicking.
"We're not a bit worried," chuckled Tulelake Police Chief Joseph Galeoto. "Not one concerned person has even called the city for instructions on what to do in an emergency."
Says Mayor Al Kongslie, a retired farmer and gas company worker, "This doesn't bother me any. There are a lot of other things that bother me more. No one here feels it's any threat at this time."
The Geological Survey won't challenge that assessment for the moment. Responding to the autumn swarm of small earthquakes measuring 4.2 and below on the Richter Scale, the geologists have installed seven seismographs around Medicine Lake, a highland haven surrounded by trees and particularly attractive to hunters and hikers at an altitude of 6,600 feet about 35 miles northeast of Mount Shasta.
Survey scientists warn that the volcano could be in the early stages of a comeback similar to the spectacular 1980 reawakening of Mount St. Helens, a sister mountain in the Cascade chain.
What's happening at Medicine Lake volcano, which takes its name from the bucolic body of water that fills about one-fourth of the volcanic caldera, actually resembles events of the last several years near Mammoth Lakes, Calif., more than what happened at Mount St. Helens. Also occupying part of the site of a long-dormant volcano, Mammoth Lakes, a popular ski resort in the eastern Sierra Nevada Mountains, is rattled sporadically by earthquake swarms apparently spurred by white-hot subterranean magma.
The difference: Where Mammoth Lakes has felt quakes for years, before September only one earthquake had been detected at Medicine Lake since scientists placed a a single seismograph there in 1981. But more than 200 suddenly occurred in one two-day period this fall.
"Mammoth has gotten us more nervous at times," said Evans. "But it's not surprising people were panicked briefly (by the Medicine Lake earthquake swarm).