October 21, 2002

BEND - Remember that volcanic bulge on the west flank of the South Sister? It's still there, and geologists say it's still growing.

At issue is whether the tallest of the Three Sisters is getting ready to blow its top after 2,000 years of dormancy.

"We don't know the answer to that, but if things have fundamentally changed and the system is moving into a state of eruption, there will be a whole lot of signs," said Willie Scott, the scientist in charge at the Cascades Volcano Observatory.

"There will be lots of earthquakes and ground deformation, and we will detect more volcanic gases in the streams."

The bulge spans an area of about 10 miles and is bulging upward at a rate of about an inch a year. Hikers won't notice it but geologists have, and they say it is telling them a great deal.

Volcanologists from the U.S. Geological Survey continue to collect data to determine if the bulge is the predecessor to an eruption.

Since 1997, scientists have been studying satellite pictures of the area. The bump has become a bulge as magma and other debris gathers in a chamber about three miles deep.

"The bulge is still growing, and the ground deformation is continuing at the same rate," said Scott.

To scientists, that is still compelling news. The discovery of the bulge and the subsequent monitoring of its growth has afforded earth scientists the rare opportunity to watch the growth of a potential volcanic eruption from its earliest stages.

Its continuous swelling likely indicates the gathering of a pool of magma, gases and other matter.

Rarely have scientists been able to observe such subtle changes on the earth's surface. Typically, low-level earthquakes or actual field work where scientists measure the ground reveal subsurface volcanic activity.

"What has happened since 1997 probably isn't special," Scott said. "But we know that the volume of material intruded in the area over the past few years is probably 10 times more than normal."

Unresolved is whether the system beneath the earth's crust is maintained by periodic increases of debris or whether there is a marked increase in the rate at which magma accumulates, Scott said.

The most recent earthquake in the area occurred on Jan. 18 at an intensity of 2.4. Scientists have placed equipment to measure earthquakes in and around the mountain, which has a crater of its own at the summit containing the highest crater lake in North America.

They also rely on satellite images taken by the European Space Agency to provide data on the area.

Scott warned that people should not be complacent about the bulge. Because there are few earthquakes right now and no other dramatic changes in the gases in the streams around the bulge, its existence may seem more interesting than auspicious, he said.

But there is a safety component, and scientists want to use the information they gather to more accurately predict if there is an eruption risk.

(Copyright 2002 by The Associated Press. All Rights Reserved.)

-- Anonymous, October 21, 2002