Portions of this article include public domain text from the USFS Deschutes & Ochoco National Forests - Crooked River National Grassland.
The Western Cascades is a region of Oregon, USA containing many shield volcanoes, cinder cones and lava flows. The region was volcanically active from approximately 5-0.5 million years ago. The province is characterized as an older, deeply eroded volcanic range lying west of the more recent snow-covered High Cascade Range. They range in elevation from 1700 feet on the western margin to 5800 feet on the eastern margin. The Western Cascades began to form 40 million years ago with eruptions from a chain of volcanoes near the Eocene shoreline. Volcanic activity gradually shifted to the east in the Miocene and Pliocene.[1]
The Western Cascades are made up almost entirely of slightly deformed and partly altered volcanic flows and pyroclastic rocks which range in age from late Eocene to late Miocene. These rocks have been heavily dissected by erosion and the only evidence remaining of the many volcanoes from which they were erupted are occasional remnants of volcanic necks or plugs which mark former vents. There are also minor Pliocene to Pleistocene intracanyon lavas derived from the High Cascades or rare local vents. From youngest to oldest, the Western Cascade Range consists of four main units:[1]
Contents |
Name | Elevation | Location | Last eruption | |
meters | feet | Coordinates | ||
Armet Creek[2] | - | - | - | ~0.56 million years ago |
Bachelor Mountain[2] | - | - | - | - |
Battle Ax Mountain[2][3] | - | - | 1-2 million years ago | |
Crescent Mountain[2] | - | - | - | - |
Harter Mountain[2] | - | - | - | - |
High Prairie (Oregon)[2] | - | - | - | ~1.98 million years ago |
Iron Mountain[2] | - | - | - | - |
Snow Peak[2] | - | - | - | ~3 million years ago |
Three Pyramids[2] | - | - | - | - |
du Bray, E.A.; D.A. John, D.R. Sherrod, R.C. Evarts, R.M. Conrey, and J. Lexa (2006). Geochemical database for volcanic rocks of the Western Cascades, Washington, Oregon, and California. Reston, Virginia: United States Geological Survey. pp. 49p. ISBN 1411309294. http://pubs.usgs.gov/ds/2006/155/.