Intermountain Basins
This vast and topographically diverse space is bounded on the east by the Rockies and on the west by the Cascades and the Sierra Nevada. In this “basin and range” landscape, geology is made visible as an ever-present force that has written Earth’s history, layer upon layer. The Intermountain Basins include the dramatic red-rock canyons of the Colorado Plateau, the Great Salt Lake, thousands of square miles of sagebrush terrain, and some of the nation’s greatest wilderness areas and national parks. This vast and topographically diverse space is bounded on the east by the Rockies and on the west by the Cascades and the Sierra Nevada. In this “basin and range” landscape, geology is made visible as an ever-present force that has written Earth’s history, layer upon layer.
Location
The basins between the pacific mountain ranges of the Cascades and Sierra Nevada, east to the Rocky Mountains.
Climate
Mean annual temp. 10.6ºC, mean annual precip. 414mm @ Salt Lake City, UT [1300m elevation]); drought in June, July, August
Features
Basin and range physiography with extensive closed basin valleys between low mountain ranges – best developed in the heart of the Great basin in Nevada. The dramatic red-rock canyons of the Colorado Plateau formed from continental upwarping and subsequent river erosion. The "sagebrush ocean" predominates these landscapes, with dry semi-desert forms occurring throughout the Great Basin, while grass-dominated sagebrush steppe was historically characteristic across Columbia Plateau. Palouse Prairie was common throughout orchard country of eastern Washington. In higher elevations, Pinyon-juniper woodlands dominate this Division.
History and Trends
Densely populated only in selected locations; around Salt Lake City, eastern Washington, and southern Idaho, where irrigation supports extensive agriculture. Ancestral Pueblo lived in cliff dwellings throughout the Colorado Plateau. Scenic national parks and recreation areas are common throughout this division. But there is also intensive development of coal and uranium mines, and newly intense exploitation of natural gas. Invasive non-native plants, such as cheatgrass in the sagebrush and pinyon-juniper, or salt cedar in the riparian zones, have had profound effects on native ecosystems. In some cases, introducing fire regimes to systems formerly lacking natural fire, or severely altering regimes where they occurred historically.
Intermountain Basins Ecoregions
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Colorado Plateau Ecoregion
The Colorado Plateau falls primarily within the Colorado River watershed, which defines much of its mid-elevation character between the Rocky Mountains (eastward) and the Mojave and Sonoran Deserts (southwestward). To the north and northwest, a grand staircase of cliffs ascends into the adjacent Utah High Plateaus.
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Columbia Plateau Ecoregion
The Columbia Plateau is a broad expanse of sagebrush covered volcanic plains and valleys, punctuated by isolated mountain ranges and the dramatic river systems of the Snake, Owyhee, Boise and Columbia.
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Wyoming Basins Ecoregion
The Wyoming Basins ecoregion comprises 51,605 square miles of basin, plain, desert, and island mountains in Wyoming, Montana, Idaho, Colorado, and Utah.