The Volcanoes of the Three Sisters Area, Oregon

Situated on the Cascade plateau, the region known as the Tumalo Volcanic Center was active in the Pleistocene epoch with explosive eruptions between 700,000 and 170,000 years ago that left extensive pyroclastic deposits on which basaltic and basaltic andesitic lava flows formed a great number of shields. One of these eruptions resulted in tephra deposits as…