Three Sisters Wilderness

The Three Sisters Wilderness is a wilderness area in the Cascade Range, within the Willamette and Deschutes National Forests in Oregon, USA. It comprises 286708acre, making it the second largest wilderness area in Oregon, after the Eagle Cap Wilderness. It was established by the United States Congress in 1964 and is named for the Three Sisters volcanoes. The wilderness boundary encloses the Three Sisters as well as Broken Top, which is southeast of South Sister.Oregon Route 242 separates the Three Sisters Wilderness from the Mount Washington Wilderness to the north, while the Waldo Lake Wilderness shares the southern boundary.GeologyMany types of landforms make up the wilderness area, but the most common are volcanic features, the most notable being the Cascades which are stratovolcanoes having formed around 1.6 million years ago. Numerous cinder cones have formed on their flanks as well as many lava flows that contain hundreds of lava tubes.