Mammoth Shakes, Rattles and Rolls : Sierra: Long Valley’s terra isn’t so firma, thanks to an active volcano. Land rises; creeks boil; trees die from volcanic gases. But that’s nothing new, and residents aren’t worried.

MAMMOTH LAKES, Calif. — The earth beneath this resort town seems cursed.

The ground shakes, rises and spits steam. It belches gases that kill trees. It boils creeks.

There is a volcano below Mammoth Lakes. The U.S. Geological Survey calls it among the most likely in the lower 48 states to erupt in coming decades, though no eruption is imminent or even certain.

Most residents aren’t worried.

“It’s just too beautiful here to worry about the volcano,” said Danielle Lane, 23, who recently moved to the resort town of 5,000.

“I’m not moving,” said Bradley Foster, 33, a natural gas company employee.

This Sierra Nevada village sits at the edge of what is called Long Valley. The valley is really a 9-mile-wide, 19-mile-long collapsed volcanic crater. Scientists call it a caldera, the Spanish word for caldron.

Long Valley, 250 miles north of Los Angeles, is the most restless volcano among more than a dozen in Washington, Oregon and California, said USGS volcano expert C. Dan Miller. Mt. Shasta and Lassen Peak in Northern California are also among the more likely to erupt again. The last to erupt was Mt. St. Helens, near Vancouver, Wash., in 1980.

Earth movement and other signs of unrest around Mammoth Lakes are caused by molten rock that rumbles around about four miles underground, said David Hill, who monitors Long Valley for the USGS.

Underground vents cause some creeks to boil, spew steam and reek of sulfur. Carbon dioxide seeping through the ground has killed thousands of pine trees and forced closure of Horseshoe Campground to overnight camping because of the high concentrations of the gas.

About 760,000 years ago, the volcano blew mountains of debris halfway across the continent in one of the planet’s most powerful eruptions. It spewed 130 cubic miles of material, 600 times more than the eruption of Mt. St. Helens.

The Long Valley eruption formed a spectacular resort site, ringed by mountains resembling those 20 miles west in Yosemite National Park. Mammoth Lakes draws up to 30,000 tourists in a day.

“The volcano is part of the attraction,” said 18-year-old visitor Alexandra Campbell of Encinitas.

Community leaders don’t see the volcano as a hindrance to growth in Mammoth Lakes, which started as a mining camp in the mid-1800s.

“It’s not a requirement or a feeling on our part that it should affect land-use planning,” said Mammoth Lakes City Manager Glenn Thompson.

City codes require strong buildings, but that’s to handle the region’s heavy snowfall, not volcanic fallout, Thompson said.

Not everyone is so nonchalant.

Amy Corsinito, 19, of Encinitas, said her parents like to visit but are hesitant about buying a house.

“You can’t get volcano insurance,” she said.

The movement of lava in two underground chambers during the last 15 years has raised the center of Long Valley by more than two feet. It also has caused tens of thousands of earthquakes, most of them in the range of magnitude 1 to 3.

In May, 1980, four earthquakes of about 6 caused minor damage.

People here are gambling that the earth won’t suddenly explode. Experts say it’s a good bet. Odds are overwhelming that a major eruption would provide days or weeks of warning.

“Other places in California shake, rattle and roll, or flood, or burn,” said longtime resident Jack Clausen.

Discussing the strength of a recent quake, Clausen said, “That’s nothing. I’ll show you a 3.0 quake.” The forestry worker kicked the bumper of his truck. “That’s a 3.0.”

Some people are even more skeptical.

“I’m from Southern California, where there’s always a disaster. This is no big deal,” said visitor Alan Fuller, 20, of Yorba Linda.

The volcano’s restlessness caused the USGS to issue a “notice of potential volcanic hazard” in 1982. The warning, coupled with quakes, damaged tourism and the real estate market and angered local business people.

“We’ve never stepped back from saying there have been eruptions in the past and there will be again in the future,” Miller said.

But the USGS dropped its official warning in 1984.

The rugged beauty of volcanoes throughout the West attracts people. Towns sit near at least four volcanoes.

Local government officials said volcanic hazards are usually discounted when policy boards consider development. Many of the towns were well established long before serious consideration of the dangers, officials said.

Three towns hug the base of Northern California’s Mt. Shasta, 260 miles north of San Francisco. Two of them, Weed and the town of Mt. Shasta, have lured New Age enthusiasts who believe the volcano has mysterious powers.

Other residents said they have seen refugees from a lost continent and UFOs on the 14,161-foot mountain.

Mt. Shasta is believed to have last erupted in 1786. It’s also considered among the most likely in the Lower 48 to erupt again, but less so than Lassen Peak, 70 miles southeast.

Eruptions last occurred at 10,457-foot Lassen Peak from 1914 to 1921. Lassen Peak, which is surrounded by a national park, is the southernmost volcano in the Cascade Range, which also runs through Washington and Oregon.

The Cascade volcanoes are cone-shaped vents left over from eruptions, unlike Long Valley.

USGS volcano experts in the West carry electronic pagers in case volcanic activity increases. Mostly, they watch Long Valley.

“I have a beeper on my belt that I’ve been carrying for the last 13 years . . . that if something develops at Long Valley, I’d get a call,” Miller said.

“We don’t want to cause a scare,” he said. “We could continue to be in this mode for a long time. If something changes, we’re confident we could provide a warning.”

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Rating the Volcanoes

Volcanoes are a vent in the earth’s crust through which molten rock is ejected. They often form a cone-shaped mountain. Scale of eruption likelihood for West Coast volcanoes, developed by Stephen Malone of the University of Washington:

1 -- Most likely within 75 years

2 -- Likely, but may be a longer wait

3 -- Less likely and possibly extinct

4 -- Probably extinct

LONG VALLEY

Eruption likelihood: 1+

Last activity: About 760,000 years ago.

Location: About 250 miles north of Los Angeles in southeastern California, east of Yosemite National Park.

LASSEN PEAK

Elevation: 10,457 feet

Eruption likelihood: 1

Last activity: 1914-1921

Location: Northern California, 50 miles east of Redding.

MT. SHASTA

Elevation: 14,161 feet

Eruption likelihood: 1-

Last activity: Probably 1786

Location: Northern California, 260 miles north of San Francisco.

Eruption likelihood for other West Coast volcanoes:

Crater Lake in Oregon

Eruption likelihood: 2-

Mt. Hood in Oregon

Eruption likelihood: 1

Mt. Adams in Washington

Eruption likelihood: 3+

Mt. St. Helens in Washington

Eruption likelihood: 1+

Mt. Rainier in Washington

Eruption likelihood: 1

Mt. Baker in Washington

Eruption likelihood: 1

Source: Associated Press