Three Sisters

The Three Sisters are volcanic peaks of the Cascade Volcanic Arc in Oregon. Each exceeding 10,000 ft (3,000 m) in elevation, they are the third-, fourth-, and fifth-highest peaks in Oregon. They are often seen as one unit, but the three mountains evolved under differing geologic situations, and the petrologic composition of each mountain can vary significantly. Whereas North Sister is extinct and Middle Sister is dormant, South Sister (most popular for climbing and scrambling) last erupted about 2,000 years ago and could still erupt.