Three Sisters (Oregon)

Three Sisters
The Three Sisters, looking north
Highest point
Elevation	South  10,358 ft (3,157 m) Middle 10,047 ft (3,062 m) North   10,085 ft (3,074 m)
Prominence	South  5,598 ft (1,706 m) Middle 1,127 ft (344 m) North   2,725 ft (831 m)
Listing	US most prominent peaks 85th
Coordinates	44°06′12″N 121°46′09″W / 44.103449°N 121.7692058°W / 44.103449; -121.7692058Coordinates: 44°06′12″N 121°46′09″W / 44.103449°N 121.7692058°W / 44.103449; -121.7692058
Geography
Three Sisters Location in Oregon
Location	Lane and Deschutes counties, Oregon, U.S.
Parent range	Cascade Range
Topo map	USGS South Sister and North Sister
Geology
Age of rock	Quaternary
Mountain type	Complex volcano, made up of stratovolcanoes and a shield volcano
Volcanic arc	Cascade Volcanic Arc
Last eruption	50 BCE (?)
Climbing
Easiest route	Hiking or scrambling, plus glacier travel on some routes

The Three Sisters are a complex volcano of three volcanic peaks of the Cascade Volcanic Arc and the Cascade Range in the U.S. state of Oregon. Each exceeding 10,000 feet (3,000 m) in elevation, they are the third-, fourth-, and fifth-highest peaks in the state of Oregon, and are located in the Three Sisters Wilderness, about 10 miles (16 km) south of the nearest town of Sisters. Diverse species of flora and fauna inhabit the area on and around the mountains, which is subject to frequent snowfall, occasional rain, and extreme temperature differences between seasons. The mountains, particularly South Sister, are popular for climbing and scrambling.

Although they are often grouped together and seen as one unit, 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 last erupted about 2,000 years ago and still could erupt, threatening life within the region. After satellite imagery detected tectonic uplifting near South Sister in 2000, the United States Geological Survey made plans to improve monitoring in the immediate area.

The Three Sisters are located on the boundaries of Lane and Deschutes counties and the Willamette and Deschutes national forests in the U.S. state of Oregon, about 10 miles (16 km) south of the nearest town of Sisters. The three peaks, the third-, fourth-, and fifth-highest peaks in Oregon, have 15 named glaciers among them, nearly half of the 35 named glaciers in Oregon. The Sisters were named Faith, Hope, and Charity by early settlers, but "these names have not prevailed", and instead they are named North Sister, Middle Sister, and South Sister.