Mount Hood still rumbles at times

By The Associated Press

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But the tallest mountain in Oregon has been restless recently, with swarms of earthquakes rumbling beneath it about once a year. Hot gas and steam occasionally spew from vents in crags near its 11,240-foot peak.

The U.S. Geological Survey (USGS) monitors the vents, called fumaroles, for carbon dioxide and sulfur dioxide, potentially deadly gases that could signal a potential eruption, said John Ewert, geologist and volcanologist at the agency's Cascades Volcano Observatory, in Vancouver, Wash.

The odds of Mount Hood erupting lava and hot mud down its flanks over the next 30 years range from 1-in-15 to 1-in-30, according to the USGS.

Earthquakes and venting on Mount Hood in recent years show no indication the mountain has been preparing to erupt. But the threat remains, Ewert said.

Mount St. Helens, just 55 miles to the north, has been grabbing attention lately with its own earthquake swarms that have triggered warnings of a possible eruption.

But other volcanoes in the region have been making noises of their own. Last March, small earthquakes shook an area west of the Three Sisters in Central Oregon. Gases from magma have been detected near springs at the base of the connected trio of Cascades peaks. In addition, a large bulge has grown over the past seven years near the volcanoes.

The bulge is the largest sign of recent volcanic activity in the state, said Jon Major, another geologist with the observatory.

"Scientists did some modeling on what it would take to create that type of bulge, and they found it would take certain amounts of magma," he said.

"The bulge is growing, but it hasn't accelerated," Major added.

A Three Sisters eruption is unlikely without more intense activity, such as hundreds or thousands of small quakes and emissions of volcanic gases, scientists say.

Copyright © 2004 The Seattle Times Company

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