Global Volcanism Program | Image GVP-03232
Medicine Lake Volcano's summit caldera is seen here from the east rim, with Mount Shasta in the background. The 7 x 12 km caldera, the source of Medicine Lakes largest eruption, (~180 ka) is partially filled by Medicine Lake, Medicine Lake Glass Flow (on the right) that erupted ~5,200 years ago, and the older Lake Basalt flow (~89 ka; in the foreground). During the Holocene several obsidian flows have erupted inside and along the rim of the caldera with large pumice deposits, and voluminous basalts have erupted on the flanks.
Photo by Peter Lipman, 1981 (U.S. Geological Survey).