LOCATION MOSSYROCK WAEstablished Series
TAXONOMIC CLASS: Medial, amorphic, mesic Pachic Melanoxerands
TYPICAL PEDON: Mossyrock silt loam - pasture. (Colors are for moist soil unless otherwise stated. When described the entire profile was moist.)
Ap--0 to 8 inches; black (10YR 2/1) silt loam, very dark grayish brown (10YR 3/2) dry; weak very fine granular structure; slightly hard, friable, nonsticky, nonplastic and weakly smeary; many roots; moderately acid (pH 5.8); abrupt smooth boundary. (7 to 8 inches thick)
A1--8 to 21 inches; black (10YR 2/1) silt loam, very dark grayish brown (10YR 3/2) dry; moderate very fine granular structure; slightly hard, friable, nonsticky, slightly plastic and weakly smeary; many roots; slightly acid (pH 6.4); gradual wavy boundary. (11 to 16 inches thick)
A2--21 to 30 inches; dark reddish brown (5YR 2/2) silt loam, dark grayish brown (10YR 4/2) dry; weak medium prismatic structure; slightly hard, friable, nonsticky, slightly plastic and weakly smeary; many roots; slightly acid (pH 6.4); clear irregular boundary. (4 to 10 inches thick)
Bt1--30 to 48 inches; dark brown (7.5YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry; weak medium prismatic structure; slightly hard, friable, slightly sticky, slightly plastic and weakly smeary; few roots; many fine tubular pores; thin patchy clay films in pores; strongly acid (pH 6.6); gradual wavy boundary. (16 to 21 inches thick)
Bt2--48 to 63 inches; dark brown (7.5YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry; weak medium prismatic structure; hard, firm, slightly sticky, slightly plastic and weakly smeary; few roots; many fine tubular pores; thin patchy clay films in pores; strongly acid (pH 5.4); gradual wavy boundary. (13 to 17 inches thick)
Bt3--63 to 76 inches; dark brown (7.5YR 4/4) silt loam, light yellowish brown (10YR 6/4) dry; common fine faint light gray (10YR 7/1) mottles on surfaces of peds; weak medium prismatic structure; hard, firm, slightly sticky, slightly plastic and weakly smeary; few roots; many fine tubular pores; thin patchy clay films in pores; moderately acid (pH 5.6)
TYPE LOCATION: Lewis County, Washington about 2.5 miles west of Mossyrock; 50 feet north, 425 feet west of southeast corner sec. 11, T. 12 N., R. 2 E. W.M.
RANGE IN CHARACTERISTICS: The solum thickness is more than 60 inches. Mossyrock soils are usually moist but are dry for 45 to 60 consecutive days following the summer solstice. The particle-size control section contains less than 60 percent vitric volcanic ash. The umbric epipedon is 24 to 34 inches thick. The mean annual soil temperature at a depth of 20 inches ranges from 47 degrees to 52 degrees F.
The A horizon has hue of 10YR through 5YR, value of 2 or 3 moist, 3 to 5 dry, chroma of 1 to 3 moist or dry. It has weak or moderate granular or subangular blocky structure. It is moderately acid or slightly acid.
The Bw horizon has hue of 7.5YR or 10YR, value of 4 through 6 moist, 5 through 7 dry, and chroma of 3 or 4 moist or dry. It is strongly acid to neutral.
COMPETING SERIES: This is the Washougal series. Washougal soils have 2C sandy-skeletal horizons at depths of 24 to 40 inches.
GEOGRAPHIC SETTING: Mossyrock soils are on terraces at elevations between 300 to 1,000 feet. Slopes are 0 to 15 percent. These soils formed in volcanic ash and loess. Mossyrock soils occur in a marine type climate with 55 to 70 inches average annual precipitation occurring mostly as rain during the winter. Mean January temperature is 35 to 38 degrees F., mean July temperature is 61 to 63 degrees F., and mean annual temperature is about 50 degrees F. The average frost-free season is 150 to 200 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing Cinebar soils and the Klaber, lacamas, Olympic, Prather, and Salkum soils. Klaber and lacamas soils have an aquic moisture regime and an argillic horizon. Olympic, Prather, and Salkum soils have an argillic horizon.
DRAINAGE AND PERMEABILITY: Well drained; slow runoff; moderate permeability.
USE AND VEGETATION: Used mostly for cropland. Some is used for woodland. Common crops are hay and pasture, blueberries, small grains, raspberries, and blackberries. Native vegetation is Douglas-fir, red alder, bigleaf maple, and western redcedar with an understory of Salal, Oregon-grape, western brackenfern, western swordfern, vine maple, red huckleberry, trailing blackberry, Pacific trillium, scotch-broom and thimbleberry.
DISTRIBUTION AND EXTENT: Southwestern Washington. Series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Lewis County, Washington, 1941.
REMARKS: This draft refelcts change in classification from medial, mesic Pachic Melanoxerands to medial, amorphic, mesic Pachic Melanoxerands.
Diagnostic horizons and features recognized in this pedon include:
Umbrick epipedon - from 0 to 30 inches (Ap, A1, A2 horizons)
Cambic horizon - from 30 to 76 inches (Bt1, Bt2, Bt3 horizons)
Particle-size control section - from 0 to 40 inches.