Volcanic Hazard Downgraded at Mammoth--at Least on Paper

Times Science Writer

Of all the changes that have taken place recently at this popular ski resort--and there have been many--none has been more warmly received by the local community than the U.S. Geological Survey's downgrading of the area's volcanic hazard.

The revision was made by the highest officials of the agency with little participation by working-level scientists who have been studying the area. The status of the hazard has changed more on paper--because of the agency's new criteria for defining geological situations--than in reality, according to many of those scientists.

Nevertheless, merchants, politicians and townspeople alike approve of the change. They have tended to blame their economic woes of the last few years on what they considered to be a greatly overstated threat of lava movement below the surface, just a few miles southeast of the center of this newly incorporated town.

But now that the sales of condominiums and other properties have perked up, and the deep snows on the slopes of nearby Mammoth Mountain hold the promise of another profitable skiing season, the talk of the town has turned to the future. There are ambitious plans afoot for a new ski bowl near Mammoth's often-crowded slopes, an 18-hole golf course for summer and autumn use and a high-rise hotel with a convention center.

Amid all this optimism, the last thing local people want to talk about is the volcanic situation--even the geological survey's de-emphasis of its likelihood.

"Is volcano a dirty word?" one man said. He pondered the question and then answered: "Very much so." Said another: "Boy, you just never hear the word spoken around here anymore. It's almost as if they passed a law against saying it aloud."

Displeasure, however, cannot brush aside the reality that violent upheavals have played a major role in shaping the Eastern High Sierra--a reality that was forcefully underscored on Nov. 23, 1984, when the region was shaken by a magnitude 5.7 earthquake and an unusually vigorous string of smaller aftershocks. Indeed, it was a temblor in 1978 of almost the same size and almost in the same place that set off the train of events leading to the issuance of the volcanic notice.

This oval-shaped valley, a corner of which is occupied by the town and its popular ski mountain, is really a caldera--a volcanic crater that was created about 700,000 years ago by a mighty eruption. Since then, other eruptions have reshaped the local terrain. The Inyo craters and domes, for example, were formed by smaller blasts a few hundred years ago.

During the 1980 Memorial Day weekend, the region was jack-hammered by four earthquakes of magnitude 6 to 6.2 on the Richter scale. It was unusual to have that many strong temblors within such a short span, and when those shocks were accompanied by new hot springs and hotter-than-usual water in existing hot pools, scientists took notice.

Measurements showed that the valley floor was both rising rapidly and spreading outward. When several swarms of small quakes hit the area in late 1981 and early 1982, the most logical interpretation of all these phenomena seemed to be that magma--molten rock--was once again forcing its way toward the surface. Concerned, the Geological Survey issued a volcano notice, the lowest of three levels of hazard warning.

Concern turned to alarm in January, 1983, when a large and prolonged swarm of temblors hit the valley. Scientists thought it looked a lot like the swarms that had preceded the 1980 explosion of Mt. St. Helens volcano in Washington, and they were on the verge of upping the hazard stakes to a watch, the second level of warning.

But the Geological Survey scrapped the three-level warning system--notice, watch and warning--last spring and replaced it with a two-tier system--informal and formal alert.

With the criteria changed, with seismic activity greatly reduced from the previous 18 months and with the valley floor not deforming as much as it had earlier, the Geological Survey declared last summer that "a volcanic eruption does not now pose an immediate threat to public safety in the (Mammoth Lakes) region."

Since that statement, "morale has gone up and people feel things are moving ahead, " said Gary Flynn, the mayor pro tem of Mammoth Lakes.

Alan O'Connor, an architect, agreed: "The atmosphere here is changing very quickly, and it's because the USGS has taken the volcano notice off the area."

Indeed, in making the revisions, the Geological Survey has given many here the impression that it has totally reversed itself about the possibility of volcanism in Long Valley.

Not so. "The geology hasn't really changed," said Roy Bailey, a geophysicist with the Geological Survey who has been studying Long Valley for several years. "We're still dealing with the same problem, a progressing situation."

"(It) doesn't mean we're not concerned about Mammoth Lakes or Long Valley," said Dallas Peck, director of the U.S. Geological Survey, and the person responsible for the revised warning system and the changed assessment. "The seismicity is continuing there and we are continuing to watch things closely."

'Didn't Please a Lot of Us'

Then why was the agency's old warning system discarded? Why was the Long Valley hazard de-emphasized? And why were these changes made without consulting the scientists who have been most directly involved with studies of the area?

The change in the warning system "was done in the director's office, and it was a high-level decision," said one federal scientist, declining to be identified by name. "It didn't please a lot of us. We were concerned this change would . . . be used against those of us who regard the situation there seriously."

"No one was advised of the change from a 3-level to a 2-level warning system in advance," said another, who also asked to remain anonymous. "The change came at a time when the merchants and the construction companies began complaining about the (economic) impact of the volcano notice."

Flynn, chairman of the Mono County Republican Party as well as mayor pro tem, readily conceded that he and others had mounted a vigorous lobbying campaign to get the federal agency to modify its release of information. "We made phone calls and wrote letters," he said. "We did everything we could to get responsible statements from the USGS."

Peck and James Devine, the agency's assistant director for engineering geology, said in a conference call that their agency was not pressured either by the Interior Department, of which it is a part, or by Congress to make the changes. "I'm not saying we didn't get a lot of critical letters from Mammoth people," Peck said, "but that did not sway us."

According to Peck and Devine, the old warning system, which had been adapted years ago from a National Weather Service scheme, was looked at and found to be wanting. "It worked well for hurricanes and other things you could see coming, things you can predict," Peck said, "but it didn't work as well for geologic hazards, things like earthquakes, eruptions, landslides and other things you can't predict."

Abrupt Start

Devine defended the exclusion of rank-and-file scientists from the decision-making process, saying: "The responsibility for defining hazards rests with Reston (the agency's Virginia headquarters). That new definition (of hazards) was not discussed with working-level scientists, although we did discuss its application to the Mammoth Lakes situation."

Under the new system, the agency will keep tabs on potentially hazardous situations--an active seismic zone, for example, or a volcano or an unstable mountainside--and, as long as nothing ominous is seen, pass along on an informal basis to local officials and the public whatever information its scientists gather.

If changes are noticed that suggest the seismic zone might be about to rupture, or the volcano to explode, the agency would issue a formal warning to the affected area so that officials and people could take appropriate safety precautions.

The magnitude 5.7 earthquake in Round Valley, midway between here and Bishop, last Nov. 23 and its string of potent aftershocks proved that seismic activity can start as abruptly as it can drop off. Indeed, seismic activity is continuing today, although the magnitudes and frequencies have been less than what they were in 1983.

A swarm of several hundred small earthquakes, three of them stronger than magnitude 3, ruffled the area for several weeks in July.

According to one school of thought, these small earthquakes are the result of a rising subterranean pool of magma eating away at layers of cool, crystalline rock 13,000 to 20,000 feet down. As the intense heat of the magma comes closer, those rock layers crack and generate earthquakes.

According to another view, the earthquakes are the result of the stretching apart of the so-called "basin-and-range" province that makes up a large sector of the western United States--Nevada, parts of California, Oregon, Idaho and Utah. Alan Ryall, a seismologist at the University of Nevada at Reno, favors this explanation. He said that when the crust becomes too thin to support its own weight, it fractures and produces earthquakes. Volcanism, in this scenario, does not necessarily go hand-in-hand with seismic activity.

"It's a sort of 'chicken and egg' argument," David Hill, the agency's scientist who has directed the monitoring effort in the valley, said of these conflicting views. "The two are so closely related you can't really separate them: As the crust thins out and is fractured by earthquakes, the magma rises toward the surface. And as the magma destroys the crust, there are earthquakes."

In the meantime, state, county and local officials continue to work out emergency response plans in the event of eruptions, earthquakes stronger than any that have struck recently and landslides.

Improvements are now being made to such key physical systems as roads and communications. The California Department of Transportation plans to widen California 203, a two-lane road that until recently was the only access into or out of town, into a four-lane highway in this year, according to Flynn.

For all that, this community's nervousness about even the mention of volcanoes sometimes leads to odd actions.

For example, the county and state have completed the construction of an alternative two-lane road that connects the north end of this small community to U.S. 395. It would provide an escape hatch if an eruption were to block California 203.

Escape Route Unmarked

People not familiar with the road's existence or purpose might have a difficult time finding it. No signs that would direct motorists to it in an emergency are to be found anywhere in town and, indeed, its existence is acknowledged only by a small highway marker just a few hundred feet short of its intersection with California 203. The marker, almost an alias, reads: "Mammoth Lakes Scenic Loop."

Flynn took credit for this euphemism, saying he saw no reason to call attention to the presence of an escape route. It would simply raise questions in the minds of people about volcanoes, he said, and that would be counterproductive to Mammoth's recovery. Should an emergency ever occur, he continued, sheriff's deputies and other law enforcement personnel know where the scenic loop is and would steer traffic to it.

Local residents like Flynn believe that this area has less to fear from a volcanic eruption in the near future than Los Angeles or San Francisco have from giant earthquakes. "That hasn't stopped (development) in those cities," he said, "and they're more likely to get hit by a big earthquake than we are to get hit by a volcano."

Ironically, Flynn and many other like him put a great deal of faith in the same people for whom they also feel a great deal of animosity: U.S. Geological Survey scientists. Even as he blames the agency and its scientists for creating Mammoth's recent economic problems, he expresses confidence in their ability to monitor whatever is happening down below and to provide ample warning. It is a confidence that the scientists are not at all sure they can fulfill.

Copyright © 2019, Los Angeles Times
EDITION: California | U.S. & World