USDA Forest Service

Deschutes & Ochoco National Forests
Crooked River National GrasslandHeader Counter


Deschutes National Forest
1001 SW Emkay Drive
Bend, OR   97702

(541) 383-5300

Ochoco National Forest
3160 N.E. 3rd Street
Prineville, OR   97754

(541) 416-6500

Crooked River National Grassland
813 S.W. Hwy. 97
Madras, OR   97741

(541) 475-9272

United States Department of Agriculture Forest Service.


Oregon Volcanoes

Broken Top Volcano


Type: stratovolcano
Activity: extinct
Last Eruption: estimated at about 100,000 yrs ago
Rock Type: predominantly basaltic andesite with interbedded andesite, dacite, and rhyodacite.
Eruptive Volume: ?
Latitude: 44.08 N
Longitude: 121.70 W
Location Maps: from TIGER Mapping Service

Topo Map from TopoZone

Broken Top Photo Menu


The Three Sisters area contains 4 large cones of Quaternary age -- North Sister, Middle Sister, South Sister, and Broken Top.

  • North Sister and Broken Top are deeply dissected and probably have been inactive for at least 100,000 years.
  • Middle Sister and South Sister are younger than the North Sister. They have both been erupting over the last 50,000 years.
  • Middle Sister was active in late Pleistocene but not postglacial times.
  • South Sister is the least dissected; its basaltic andesite summit cone has a well preserved crater. Most of South Sister predates late Wisconsin glaciation and is therefore older than 25,000 years; however, eruptions of rhyolite from flank vents have occurred as recently as 2000 years ago.


  • None


  • USGS


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USDA Forest Service - Deschutes & Ochoco National Forests
Last Modified: Wednesday, 26 November 2003 at 12:02:16 EST

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