Three Sisters (Oregon)

The Three Sisters are closely spaced volcanic peaks in the U.S. state of Oregon. Located in the Three Sisters Wilderness, they are about 10 miles south of the nearest town, Sisters. The Three Sisters have about 130 snowfields and glaciers ranging in altitude from 6,742 to 10,308 feet. Neither North Sister nor Middle Sister has erupted in the last 14,000 years, and it is considered unlikely that either will ever erupt again.

About Three Sisters (Oregon) in brief

The Three Sisters are closely spaced volcanic peaks in the U.S. state of Oregon. Located in the Three Sisters Wilderness, they are about 10 miles south of the nearest town, Sisters. The Three Sisters have about 130 snowfields and glaciers ranging in altitude from 6,742 to 10,308 feet with a cumulative surface area of about 2,500 acres. Neither North Sister nor Middle Sister has erupted in the last 14,000 years, and it is considered unlikely that either will ever erupt again. The Sisters were named Faith, Hope and Charity by early settlers, but are now known as North Sister, Middle Sister and South Sister, respectively. Their ice volume totals 5. 6 billion cubic feet. The Collier Glacier, despite a 4,900-foot retreat between 1910 and 1994, is generally considered to be the largest of the three Sisters at 160-and-a-half acres. The local area has a history of flash floods, including an event on October 7, 1966, caused by a sudden avalanche on the Prouty Glacier, which filled in the spaces left, forming moraine-dammed lakes, which are more common in Three Sisters than anywhere else in the contiguous United States. The Alpine Crest Region features the wilderness area’s most-frequented glaciers, lakes, and meadows. The area includes 260 miles of trails and many forests,. lakes, waterfalls, and streams, including the source of Whychus Creek. On the western slopes, precipitation ranges from 80 to 125 inches annually, while precipitation over the eastern slopes varies from 40 to 80 inches in the east.

Weather varies greatly in the area due to the rain shadow caused by the Cascade Range. The three peaks are the third-, fourth-, and fifth-highest in Oregon, and contain 16 named glaciers, with a total ice volume of 5.6 billion cubic feet. They are part of the Cascade Volcanic Arc, a segment of theascade Range in western North America extending from southern British Columbia through Washington and Oregon to Northern California. South Sister last erupted about 2,.000 years ago and could erupt in the future, threatening life within the region. After satellite imagery detected tectonic uplift near South Sister in 2000, the United States Geological Survey improved monitoring in the immediate area. The area is subject to frequent snowfall, occasional rain, and extreme temperature variation between seasons. It is also known as the Alpine Crest region, and this area is called the Broken Top Region. It borders the Mount Washington Wilderness to the north and shares its southern edge with the Waldo Lake Wilderness. It also borders the Willamette and Deschutes national forests, and includes the WhychUS Creek Wilderness, which is home to the world’s second-largest freshwater lake, the largest in the world, the Great Lakes National Park, and the Oregon Dunes National Park. It has a total area of 281,190 acres, making it the second- largest wilderness area in Oregon.

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