South Sister, reflected in the waters of Sparks Lake, is the highest and youngest of the Three Sisters volcanoes in the central Oregon Cascades. The summit cone of South Sister has not erupted since the late Pleistocene, but the light-colored rocks above the meadow at the left are part of a group of lava flows on the flank that were extruded about 2,000 years ago.

Photo by Dave Wieprecht, 1995 (U.S. Geological Survey).

This image is made available as a Public Domain Work, but proper attribution is appreciated.

Keywords: stratovolcano | cone | lava flow

Three Sisters