Eight years after a volcano scare incited fear, anger and economic gloom in Sierra resorts, residents are nonchalant about renewed underground lava movement that is triggering thousands of tiny earthquakes. Scientists say there is a very small chance of a volcanic eruption. But most of the quakes are too small to be felt, so ``you don't really think about it,'' said Pam Murphy, spokeswoman for Mammoth Mountain Ski Area. ``You can get hit by a car,'' she said. ``You can be in a plane crash. The chances of those are a lot higher than the chance of being killed by an earthquake or a volcano.'' ``People who are frightened left long ago. I don't believe it's a conscious concern of anyone in the community,'' said Mammoth Lakes Mayor Gordon Alper. The resort town's 4,700 permanent residents live in Long Valley, a 19-mile-long, 9-mile-wide volcanic crater known as a caldera. It is located on the east slope of the Sierra Nevada range 250 miles north of Los Angeles. The Earth's crust is being stretched apart in the region, allowing molten rock to fill half-mile-wide chambers under the caldera. The valley was created 730,000 years ago by one of Earth's most powerful eruptions, a blast that spewed 600 times more material than the May 1980 eruption of Mount St. Helens in Washington state. Eruptions somewhat smaller than Mount St. Helens' happened 550 years ago at the Inyo craters, which span Long Valley's north rim, and 650 years ago at the Mono craters, several miles north of the caldera. Despite the current activity, the probability of a major earthquake or a volcanic eruption in the area is ``less than 1 percent each year,'' said David Hill, the U.S. Geological Survey geophysicist in charge of research at Long Valley. Mono County Sheriff Martin Strelneck called such estimates ``a scientific guessing game,'' and said area residents rarely discuss the latest swarm of earthquakes, which started in May 1989. That low-key attitude contrasts with feelings of anxiety, denial and hostility when thousands of quakes - some exceeding 6 on the Richter scale - rocked the area from 1979 to 1984. During that period, subterranean molten rock pushed upward, lifting the caldera's floor. As a result, the Geological Survey issued a ``notice of potential volcanic hazard'' for Long Valley in May 1982. That warning, coupled with jarring earthquakes, damaged tourism and aggravated a recession in the once-booming real estate market. ``The community overreacted,'' Murphy said. Residents accused journalists of sensationalizing the possibility of an eruption and denounced scientists for scaring people. ``Initially we thought this was a big ploy for them to get funding from Congress,'' Alper said. The hazard notice was rescinded in 1984 after the beleaguered Geological Survey changed its warning system and seismic activity diminished, reducing the possibility of an eruption. Swarms of thousands of small quakes resumed 18 months ago and continue to rattle Mammoth Lakes, June Lake, Lee Vining and other Mono County resort towns. The temblors, most measuring 1 to 3 on the Richter scale, started beneath Mammoth Mountain. In September 1989, they shifted to the caldera, where five to 10 small quakes now happen daily. A quake estimated at 5 to 5.8 on the Richter scale shook the region last Tuesday, tumbling rocks onto Yosemite National Park's roads. It was eastern California's largest quake since 1984, but wasn't related to volcanic activity that causes the quake swarms, Hill said. Long Valley's floor continues to bulge upward as molten rock moves inside two or three chambers about four miles under the caldera, he said. The caldera floor rose about 2 feet since 1979, including 3 inches in the past year. While Long Valley ``is clearly an area that's showing unrest, large calderas can do these kinds of things over years to decades without necessarily erupting,'' Hill said. The floor of a caldera near Naples, Italy, rose 9 feet between 1970 and 1984 but didn't erupt. Comparable uplift inside a New Guinea caldera also failed to produce volcanic disaster. Nevertheless, Hill said, eastern Sierra residents are addressing the volcanic threat by developing or revising emergency plans and helping the Geological Survey prepare a new system to issue a warning if an eruption appeared likely.
California 's Long Valley is a 19-mile caldera created May 1989 by an eruption 5-10 times larger than Mount St. Helens . In May 1989 , new underground lava movement began triggering thousands of tiny earthquakes and raising the valley floor. Residents refuse to heed warnings, remembering a 1982 false alarm that damaged tourism and aggravated a recession. Afterward, journalists were accused of sensationalism and scientists of scaring people to get more funding. Currently, 5-10 small quakes happen daily as the Long Valley 's crust is stretched apart and magma fills four miles -wide chambers four miles under the caldera, but the probability of eruption is 1 percent .