Mount Jefferson rises above Breitenbush Lake to the north. The glacially eroded volcano has not erupted since the late Pleistocene, although flank vents to the south that are not associated with the main edifice have been active since 7,700 years ago.

Photo by Lee Siebert, 1995 (Smithsonian Institution).

This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.

Keywords: stratovolcano

Jefferson