LOCATION EASTRIDGE               MT

Established Series
JMS/KTS/RJS
04/2011

EASTRIDGE SERIES

The Eastridge series consists of very deep, well drained soils that formed in volcanic ash influenced alluvium and/or colluvium derived from rhyolite and other moderately fine-grained igneous rocks. These soils are on mountain slopes, hills and landslides. Slopes are 8 to 75 percent. Mean annual precipitation is about 430 mm and mean annual air temperature is about 3 degrees C.

TAXONOMIC CLASS: Ashy-skeletal, glassy Vitrandic Haplocryalfs

TYPICAL PEDON: Eastridge very cobbly ashy loam, in rangeland on a 55 percent slope at 1,870 meters elevation (colors are for dry soil unless otherwise indicated).

Oi--0 to 5 cm; slightly decomposed forest litter.

E1--5 to 15 cm; dark gray (10YR 4/1) very cobbly ashy loam, very dark gray (10YR 3/1) moist; weak medium subangular blocky structure; very friable, slightly hard, slightly sticky and slightly plastic; many very fine roots; common very fine irregular pores; 20 percent gravel, 20 percent cobbles; slightly acid (pH 6.2); clear wavy boundary. (5 to 20 cm thick)

E2--15 to 28 cm; brown (10YR 5/3) very cobbly ashy sandy loam, dark grayish brown (10YR 4/2) moist; weak medium subangular blocky structure; friable, hard, slightly sticky and slightly plastic; many very fine and common fine roots; many very fine, common fine and medium irregular pores; 20 percent gravel, 25 percent cobbles; moderately acid (pH 6.0); clear wavy boundary. (10 to 30 cm thick)

E/Bt--28 to 38 cm; E part (60 percent) is brown (10YR 5/3) very cobbly ashy sandy loam, brown (10YR 4/3) moist; slightly hard, friable, slightly sticky and slightly plastic; Bt part (40 percent) is dark grayish brown (10YR 4/2) very cobbly ashy sandy clay loam, very dark grayish brown (10YR 3/2) moist; hard, firm, moderately sticky and moderately plastic; weak coarse subangular blocky structure; common fine roots; common very fine and fine tubular pores; common discontinuous faint clay films on faces of peds; 20 percent gravel, 25 percent cobbles; moderately acid (pH 6.0); clear wavy boundary. (5 to 20 cm thick)

Bt--38 to 71 cm; yellowish brown (10YR 5/4) very cobbly ashy sandy clay loam, dark yellowish brown (10YR 4/4) moist; moderate coarse subangular blocky structure; friable, hard, moderately sticky and moderately plastic; common fine roots; common very fine and fine tubular pores; common discontinuous distinct clay films on faces of peds; 20 percent gravel, 25 percent cobbles; moderately acid (pH 6.0); clear wavy boundary. (15 to 45 cm thick)

BC--71 to 152 cm; light yellowish brown (2.5Y 6/3) very cobbly ashy sandy loam, light olive brown (2.5Y 5/3) moist; weak medium subangular blocky structure; friable, slightly hard, slightly sticky and slightly plastic; few fine roots; few fine irregular pores; 20 percent gravel, 30 percent cobbles; slightly acid (pH 6.2).

TYPE LOCATION: Butte North topographic quadrangle, Silver Bow County, Montana; 730 meters north and 475 meters west of the SE corner of section 27, T. 4 N., R. 8 W. UTM Zone 12: 378453e, 5103492n, NAD 83.

RANGE IN CHARACTERISTICS:
Soil temperature - 2 to 6 degrees C.
Depth to top of argillic horizon - 25 to 50 cm
Volcanic glass - greater than 30 percent in the coarse silt and sand fraction of one or more horizons within 76 cm

E horizons
Value: 4 to 6 dry; 3 or 4 moist
Chroma: 1 to 3; dry or moist
Texture: ashy loam, ashy sandy loam
Clay content: 12 to 22 percent
Rock fragments: 15 to 65 percent--5 to 30 percent gravel, 0 to 30 cobbles, 0 to 5 percent stones
Reaction: pH 5.4 to 6.8

E/Bt horizon (E part)
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 3 or 4; dry or moist
Texture: ashy sandy loam or ashy sandy clay loam
Clay content: 12 to 22 percent
Rock fragments: 30 to 60 percent--10 to 35 percent gravel, 0 to 30 cobbles
Reaction: pH 5.4 to 7.3

E/Bt horizon (Bt part)
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 2 or 3; dry or moist
Texture: ashy sandy clay loam or ashy sandy loam
Clay content: 18 to 30 percent
Rock fragments: 30 to 60 percent--10 to 35 percent gravel, 0 to 30 cobbles
Reaction: pH 5.8 to 7.3

Bt horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 4 or 5 dry; 3 or 4 moist
Chroma: 3 or 4; dry or moist
Texture: ashy sandy clay loam or ashy sandy loam
Clay content: 18 to 35 percent
Rock fragments: 40 to 60 percent--15 to 60 percent gravel, 0 to 30 cobbles, 0 to 2 percent stones
Reaction: pH 5.8 to 7.6

BC horizon
Hue: 10YR or 2.5Y; dry or moist
Value: 5 or 6 dry; 4 or 5 moist
Chroma: 3 or 4; dry or moist
Texture: ashy sandy clay loam or ashy sandy loam
Clay content: 10 to 22 percent
Rock fragments: 45 to 70 percent--20 to 70 percent gravel, 0 to 30 percent cobbles
Reaction: pH 5.8 to 7.8

COMPETING SERIES: There are no competing series.

GEOGRAPHIC SETTING:
Landform - mountain slopes, hills and landslides
Elevation - 1,560 to 2,380 meters
Slope - 8 to 75 percent
Parent material - volcanic ash influenced alluvium and/or colluvium derived from rhyolite and other moderately fine-grained igneous rocks
Climate - long, cold winters; cold, moist springs; short, cool summers
Mean annual precipitation - 350 to 535 millimeters, much of which falls as snow and as spring rain
Mean annual air temperature - 1 to 5 degrees C.
Frost-free period - 30 to 70 days

GEOGRAPHICALLY ASSOCIATED SOILS: Associated soils which occur on similar landforms are the Hungryhill, Germangulch and Evaro soil series. Hungryhill and Germangulch soils are moderately deep to bedrock. Evaro soils are loamy-skeletal.

DRAINAGE AND PERMEABILITY: Well drained; moderate permeability.

USE AND VEGETATION: Eastridge soils are used mainly for timber production and understory grazing. Native vegetation is mainly an overstory of Douglas-fir and lodgepole pine with pinegrass, elk sedge, Idaho fescue, rough fescue, kinnikinnick, Oregon grape, woods pussytoes and common juniper.

DISTRIBUTION AND EXTENT: Eastridge soils are of small extent in the southwestern and central Montana. MLRA - 43B.

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

SERIES ESTABLISHED: Silver Bow County, Montana, 2007.

REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - from 0 to 28 cm (Oi, E1 and E2 horizons)
Argillic horizon - from 38 to 71 cm (Bt horizon)
Particle-size control section - from 38 to 71 cm (Bt horizon)

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

Additional Information: The E/Bt does not meet the color requirement for glossic albic material.

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National Cooperative Soil Survey
U.S.A.