Skip to main content
U.S. flag

An official website of the United States government

South Sister NW flank. Right shoulder at skyline is thin sheet of m...

By Volcano Hazards Program 1905 (approx.)
South Sister northwest flank. Right shoulder at skyline is thin she...
Original Thumbnail Medium

Detailed Description

South Sister northwest flank. Right shoulder at skyline is thin sheet of mafic material from 22ka summit eruption. Red cinders in headwall cirques are layered with dipping lava flows.