The Lost Lake scoria cones, seen here from the east across Lost Lake near Santiam Pass, are the youngest known volcanic products of the Sand Mountain volcanic field. The cones formed about 1,950 radiocarbon years ago during eruptions along a N-S-trending fissure at the northern end of the Sand Mountain group. Growth of the cones blocked Lost Creek, forming Lost Lake.

Photo by Lee Siebert, 1997 (Smithsonian Institution).

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

Keywords: scoria cone

Sand Mountain Field