Global Volcanism Program | Image GVP-03071
Middle Sister, seen here from the NE near the saddle between North Sister and Middle Sister, is younger than North Sister. The steep cliffs forming the eastern flank are due to glacial erosion that exposed part of its dacite plug.
Photo by Lee Siebert, 1984 (Smithsonian Institution).
This image is made available under the Public Domain Dedication CC0 license, but proper attribution is appreciated.