The Geomorphology and Volcanic Sequence of Steens Mountain in Southeastern Oregon

Fuller, Richard

Lying in the arid sage-clad region of southern Oregon, Steens Mountain forms by far the largest topographic feature in the northwestern part of the Great Basin (fig. 1). The major central mass of the mountain consists of a great fault block, which rises gently from the west with an even slope about 25 miles in length. The block, which is but slightly dissected by erosion, is truncated on the east by a scarp, which drops abruptly to Alvord Desert, 5,500 feet below. This scarp has been rendered extremely precipitous by valley glaciation. The summit, with an elevation of approximately 10,000 feet, lies in the south central portion of Harney County, a little less than 50 miles north of the Nevada line at a point approximately midway between the California and the Idaho boundaries (fig. 2). NAME In early reports the mountain is referred to as Stein Mountain, which according to hearsay in the region is attributed to the German word meaning "stone," in reference to the magnificent exposures of rock on the eastern scarp. Subsequently the word was corrupted to "Steins." For at least the last 20 years, however, popular usage of the present generation has firmly established the derived appellation "Steens Mountain." FIELD WORK The writer's field work in the region has been distributed over seven summers varying in duration from two to nine weeks in length. The first two years were devoted to reconnaissance and to the study of the basalt of the region in comparison to the Columbia River lavas. This investigation necessitated the examination and sampling of the basalt exposed on the major fault scarps. Subsequently the origin of the structure formed a temporary objective. This culminated in 1929 in a joint publication with Aaron C. Waters on the "Nature and Origin of the Horst and Graben Structure of Southern Oregon."1 In addition to a description of the structural features, this paper included brief comments on the volcanic sequence of the region.