Cascade Range Current Update

Volcanoes in the Cascade Range are all at normal levels of background seismicity.

Other volcanoes include,Mount Baker, Glacier Peak, Mount Rainier, Mount Adams, and Mount St. Helens in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.

USGS Cascades Volcano Observatory, the Pacific Northwest Seismograph Network at the University of Washington, and the USGS Northern California Seismic Network and Volcano Hazards Team in Menlo Park, California, monitor the major volcanoes in the Cascade Range of northern California, Oregon, and Washington.

Since about 2 am PDT on the morning of 09/23 an earthquake swam has been occurring at Mount St. Helens. Through 5 P.M. PDT about 200 small (less than magnitude 1) earthquakes have been recorded at MSH. The earthquakes are occurring at shallow depths (less than 1 kilometer, or 1/2 mile) mostly under the lava dome that formed between 1980 and 1986. Such earthquakes are common at St. Helens, but a swarm with this many earthquakes has not been recorded for several years, most recently on November 3-4, 2001. The cause of such shallow swarms is uncertain, but may reflect increased ground water levels with the onset of autumn rain. Any eruption is unlikely to occur without significant additional precursory activity.

We continue to monitor the situation closely and will issue additional Updates as warranted.

Daily updates of earthquake data and other information can be found on the WORLD WIDE WEB at URL: http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity (CVO Menu - Monthly Summaries) and http://www.pnsn.org/HELENS/welcome.html (University of Washington - Seismic Updates)



Past Updates