Keeping an eye on the local volcanoes

Next Tuesday evening, October 2, the U.S. Geological Survey and the U.S. Forest Service will host a public meeting to provide local residents with information on recent developments related to volcanic activity in the nearby Three Sisters mountains.

The recent discovery of a ground uplift centered about three miles west of the South Sister has geologists scrambling to discover the cause. The "bulge" measures only up to about four inches in height but covers hundreds of square miles in a swath that sweeps across McKenzie Pass, all Three Sisters, Broken Top and Mt. Bachelor.

While scientists are not saying that the region is about to erupt, ground swelling of the type noted is often a precursor to eruptive activity.

Larry Chitwood, geologist for the Deschutes National Forest, attended a special briefing at the Forest Supervisor's office last week that charted plans for a sharp increase in geological research in the Three Sisters region.

Chitwood told The Nugget that next week's meeting in Sisters will cover a variety of subjects, starting with an overview of the eruptive history of the Three Sisters. Dr. Willie Scott, the USGS scientist in charge of the project, will talk specifically about the bulge and how it was discovered.

Scott will also explain the new instrumentation that is being used to monitor the bulge, together with ongoing gas emission and water studies that are part of the overall project.

Last week, part of Scott's team journeyed to the 8,500 foot-level of the South Sister where they took measurements and installed new monitoring equipment. One of the important steps in the process will be to compare this year's collected data to that of a 1985 study and establish a baseline for newer equipment that was not available at that time.

Chitwood also said that Scott will present information on the laser survey technology designed to prove the existence of the bulge and the extent of its size.

The final part of Scott's presentation will cover the potential ramifications of the bulge and the future of USGS plans to keep an eye on it.

Various sources have suggested that the ground uplift causing the bulge is the result of pooling magma (molten rock) approximately four miles beneath the surface. An increase in the number of minor earthquakes has also been noted in the region, although recent installation of better quality equipment is causing earthquakes to be recorded that might previously have gone undetected.

Any one of the observed phenomena is potentially evidence of increasing volcanic activity. Together, the multiple indicators have geologists flocking to the region to learn more about what is brewing in the earth's crust beneath the Three Sisters.

The public meeting that will address these recent geological developments will be held at the Sisters Fire Hall on Tuesday, October 2, from 7 to 9 p.m. The Fire Hall is located at 301 South Elm.