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Global Volcanism Program | Image GVP-04571

The steep-sided summit pinnacle of Mount Jefferson, seen here from the south, is one of the most dramatic summits of a Cascade Range volcano.  Mount Jefferson has been inactive since the late Pleistocene, allowing glacial erosion to remove the fragmental rocks of the original summit crater, exposing the more resistant rocks that cooled slowly in the central conduit. Photo by Lee Siebert, 1996 (Smithsonian Institution).

The steep-sided summit pinnacle of Mount Jefferson, seen here from the south, is one of the most dramatic summits of a Cascade Range volcano. Mount Jefferson has been inactive since the late Pleistocene, allowing glacial erosion to remove the fragmental rocks of the original summit crater, exposing the more resistant rocks that cooled slowly in the central conduit.

Photo by Lee Siebert, 1996 (Smithsonian Institution).


Jefferson