Earlier this month, the US Geological Survey (USGS) released a report stating that USGS scientists have detected a slight uplift of the ground surface over a broad area centered 5 kilometers west of South Sister volcano in the Three Sisters region of the central Oregon Cascade Range. This uplift was detected using a relatively new technique, Satellite Radar Interferometry (InSAR). InSAR uses satellite data to make radar images of the Earth's surface and then compares images from the same location acquired at different times to detect minor (a few centimeters) changes in the ground elevation. This page comes from the USGS Cascades Volcano Observatory Website, and it contains links to the May 8 press release, current hazards report (spring 2001), geologic descriptions of the Three Sisters volcanoes, color interferograms, site photographs, earthquake maps, an overview of InSAR, daily seismicity measurements, and much more. The USGS's Cascade Volcano Observatory has been featured previously in our reports (see the September 23, 1994 Scout Report for Science & Engineering
), but the Three Sisters research is particularly timely.