The University of Wyoming College of Agriculture recognizes 10 Wyoming soil zones with 45 types based on parent material, climate, biota and time. Wyoming soil varies with elevation, being generally cryic (sometimes frozen) and frigid above 7,800 feet, and frigid above 5,000 feet in the north and 6,500 in the south. Mesic (medium) soils occur at low elevations, such as along Belle Fourche River at 3,100 feet. Pergelic soil (permafrost) occurs above 10,000 feet.
Zone 1: Yellowstone Plateau soils are cryic, udic (humid) and aquic (wet). Young soils developed over recently glaciated bedrock. Soils are mainly Dystrocryepts (low base saturation, dark, humus-rich, sometimes frozen) that developed under pine and fir forests. Fine loamy Haplocryolls (minimal horizon development, dark, humus-rich, sometimes frozen) are found in mountain meadows. Cryorthents (near bedrock, sometimes frozen) occur on steep slopes. Cryaquepts are found along streams. Zone 2: The Absaroka Range is east of the Yellowstone Plateau and contains similar soils except that the parent materials are volcanic.
High Mountains and Basins
Zone 3: Middle Rocky Mountain soils in northwestern Wyoming include the Teton, Wind River, Wyoming and Big Horn mountain ranges. Soils are mesic to arid, including fine-loamy, sometimes frozen soils with low organic matter, plus similar Haplocryalfs with clay subhorizons on stable slopes. Dystrocryepts developed on slopes where the grade exceeds 40 percent. Zone 4: The Big Horn Basin between Yellowstone and the Big Horn Range has soils that are mesic and aridic fine-loamy soils over stabilized dunes or bedrock.
Powder River Basin and Black Hills
Zone 5: Northeastern Wyoming's Powder River Basin and Great Plains have mesic and aridic fine-loamy soils developed over bedrock. Clay soils with gypsum horizons occur in stream playas. Stony soils with coal clinkers occur on ridges. Zone 6: The Black Hills have Ponderosa pine forests on soils developed over calcium-rich glacial till, and fine-loamy soils with clay horizons on Tertiary alluvial fans. Fine-loamy Ustic (sometimes burned) Haplargids with clay horizons and Haplocambids with negligible B horizons occur on low grade slopes.
Laramie and Medicine Bow
Zone 7: Southeastern Wyoming is on the Great Plains. Soils are frigid, mesic and aridic fine loams developed over recent alluvial fans and bedrock, as well as fine-loamy or sandy soils along streams. Zone 8: The Laramie Mountains and Medicine Bow Range have fine-loamy soils developed on bedrock older than recent glaciation. Dystrocryepts developed over Precambrian granite. Hapludalfs with clay horizons and young Inceptisols with thin B horizons of less than 12 percent clay occur on slopes.
Wind River Mountains and Green River Basin
Zone 9: The Laramie and Wind River intermountain basin soils are both frigid and aridic and were formed on alluvial terraces along rivers. Native grasses thrive on soils with slight horizons developed over stabilized dunes. Salty, dry, frigid Natrargids support scant sagebrush and grass compared to nearby Haplargids with an argillic (clay) horizon. Zone 10: The Green River intermountain basin in southwest Wyoming has frigid, dry, loamy and fine-loamy soils developed over sand at the highest elevations. Torripsamments developed over stable and active dunes. Salty clay Natrargids developed on playas.
- Photo Credit Road To The Teton's 2 image by Lee O'Dell from Fotolia.com yellowstone image by Brett Bouwer from Fotolia.com Wyoming Bison 4 image by Lee O'Dell from Fotolia.com
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