LOCATION ERMONT MT

Established Series
Rev. GFB-KTS-RJS
04/2011

ERMONT SERIES

The Ermont series consists of shallow, well drained soils that formed in colluvium and residuum derived from volcanic tuff. Ermont soils are on escarpments, hills and ridges. Slopes are 4 to 40 percent. Mean annual precipitation is 16 inches and mean annual air temperature is about 38 degrees F.

TAXONOMIC CLASS: Ashy-skeletal, glassy Lithic Haplocryalfs

TYPICAL PEDON: Ermont gravelly ashy loam, native grassland. (colors are for dry soil unless otherwise noted)

A--0 to 4 inches; grayish brown (10YR 5/2) gravelly ashy loam, dark grayish brown (10YR 4/2) moist; weak fine granular structure; soft, very friable, slightly sticky and nonplastic; many very fine, fine, medium, and coarse roots; 20 percent gravel and 5 percent cobbles; neutral (pH 7.2); clear smooth boundary. (2 to 5 inches thick)

Bt1--4 to 10 inches; pale brown (10YR 6/3) very gravelly ashy loam, brown (10YR 4/3) moist; moderate medium and coarse subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; many fine and medium roots; many distinct clay films on faces of peds and on rock fragments; 35 percent gravel; neutral (pH 7.0); clear wavy boundary.

Bt2--10 to 15 inches; pale brown (10YR 6/3) very gravelly ashy loam, brown (10YR 5/3) moist; weak medium and coarse subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common fine and medium roots; many faint clay films on faces of peds; 45 percent gravel; neutral (pH 7.0); clear wavy boundary. (combined thickness of Bt horizons - 8 to 14 inches)

BC--15 to 19 inches; pale brown (10YR 6/3) extremely gravelly ashy loam, brown (10YR 5/3) moist; massive; soft, very friable, nonsticky and nonplastic; few fine roots; 65 percent gravel; neutral (pH 7.0); clear irregular boundary. (0 to 5 inches thick)

R--19 inches; fractured tuff bedrock; few fine roots in some cracks.

TYPE LOCATION: Beaverhead County, Montana; 2,600 feet east and 700 feet north of the southwest corner of sec. 11, T. 7 S., R. 11 W.; Latitude 45 degrees, 14 minutes 0 seconds North; Longitude 112 degrees, 54 minutes, 50 seconds West.

RANGE IN CHARACTERISTICS:
Soil temperature: 36 to 40 degrees F.
Depth to a lithic contact: 10 to 20 inches
Volcanic glass content: 30 to 90 percent in the coarse silt and fine sand fractions

Note: Some pedons may have a Cr horizon above the lithic contact.

A horizon
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 2 or 3; dry or moist
Clay content: 10 to 18 percent
Content of rock fragments: 15 to 35 percent--15 to 30 percent gravel, 0 to 5 percent cobbles
Reaction: pH 6.6 to 7.3

Bt horizons
Value: 5 or 6 dry; 4 or 5 moist
Texture: loam or clay loam
Clay content: 20 to 35 percent
Content of rock fragments: 35 to 60 percent--35 to 55 percent gravel, 0 to 5 percent cobbles
Reaction: pH 6.6 to 7.9

BC horizon
Clay content: 12 to 18 percent
Content of rock fragments: 35 to 80 percent--35 to 70 percent gravel, 0 to 10 percent cobbles
Calcium carbonate equivalent: 0 to 2 percent
Reaction: pH 6.6 to 8.4

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:
Landform - escarpments, hills and ridges
Elevation - 5,600 to 7,300 feet
Slope - 4 to 40 percent
Parent material - colluvium and residuum derived from volcanic tuff
Climate - long, cold winters; moist springs
Mean annual precipitation - 15 to 19 inches.
Mean annual temperature - 34 to 40 degrees F.
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Geohrock, Poin, and Ratiopeak series. Geohrock soils have bedrock at depths greater than 60 inches and do not have significant amounts of volcanic glass. Poin soils have a mollic epipedon. Ratiopeak soils have a mollic epipedon and have bedrock at depths greater than 60 inches.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.

USE AND VEGETATION: Ermont soils are used mainly for rangeland. Potential native vegetation is mainly Idaho fescue, bluebunch wheatgrass, prairie junegrass, and other miscellaneous forbs and shrubs.

DISTRIBUTION AND EXTENT: Ermont soils are of small extent of southwestern Montana. MLRA - 43B.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana.

SERIES ESTABLISHED: Beaverhead County, Montana, 2001.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 4 inches (A horizon
Argillic horizon - from 4 to 15 inches (Bt horizons)
Lithic contact - at 19 inches (R horizon)
Particle-size control section from 4 to 15 inches (Bt horizons)

Ermont soils have a cryic temperature regime and an ustic moisture regime.

ADDITIONAL DATA: Laboratory samples S03MT-001-011.

National Cooperative Soil Survey
U.S.A.