LOCATION VIOLA WAInactive Series
TAXONOMIC CLASS: Very-fine, mixed, superactive, mesic Vertic Endoaqualfs
TYPICAL PEDON: Viola silty clay loam - brushland on a 2 percent southfacing slope at an elevation of 540 feet. The soil was moist when described. (Colors are for moist soil unless otherwise stated).
Oi--2 to 0 inches; needles, leaves, and twigs in various stages of decomposition; abrupt smooth boundary. (1 to 3 inches thick)
A1--0 to 5 inches; very dark gray (10YR 3/1) silty clay loam, gray (10YR 5/1) dry; common fine faint reddish brown (5YR 5/4) mottles, yellowish red (5YR 5/6) dry; strong fine subangular blocky structure; hard, firm, sticky and slightly plastic; many medium and fine roots; many very fine and fine pores; a few dark manganese specks; strongly acid (pH 5.4) clear smooth boundary. (4 to 6 inches thick)
A2--5 to 9 inches; very dark gray (10YR 3/1) silty clay loam, gray (10YR 5/1) dry; common fine faint dark reddish brown (5YR 3/4) mottles, yellowish red (5YR 5/6) dry; thin gray sandy coatings on ped faces; weak medium prismatic and strong fine subangular blocky structure; hard, firm, stocky and plastic; many fine and medium roots; many manganese specks; common fine tubular pores; strongly acid (pH 5.4); clear smooth boundary. (0 to 6 inches thick)
Btg1--9 to 23 inches; dark grayish brown (10YR 4/2) clay, dark gray (10YR 4/1) dry; few medium distinct reddish brown (5YR 4/4) mottles, yellowish red (5YR 4/6) dry; strong coarse prismatic and moderate medium angular blocky structure; very hard, extremely firm, sticky and very plastic; many fine and very fine, and few medium roots; about 5 percent pebbles 2 to 5 mm in diameter; many fine and few coarse tubular pores; thin continuous clay films on vertical faces at prisms, top and bottom of coarse prisms have thick continuous clay films and slickensides; strongly acid (pH 5.4); gradual smooth boundary. (10 to 15 inches thick)
Btg2--23 to 60 inches; dark grayish brown (10YR 4/2) clay, dark gray (10YR 4/1) dry; many medium distinct reddish brown (5YR 4/4) mottles, yellowish red (5YR 5/6) dry; strong, coarse prismatic structure and moderate fine angular blocky structure; very hard, extremely firm, sticky and very plastic; few fine and medium roots at a depth of 26 inches, very few very fine roots to a depth of 30 inches, none below; 5 percent gravel; many fine and few medium pores to a depth of 30 inches, common very fine tubular pores below 30 inches; thin continuous clay films on vertical faces of prisms, top and bottom of coarse prisms have thick continuous clay films and slickensides; neutral (pH 6.6).
TYPE LOCATION: Cowlitz County, Washington. Approximately 13 miles east of Castle Rock. About 320 feet north of Sightly Road and about 320 feet north and 600 feet east of the southwest corner of section 32, T. 10 N., R 1 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature at 20 inches ranges from 50 to 54 degrees F. Solum thickness exceeds 60 inches. Coarse fragments range from 0 to 5 percent.
The A horizon is 5 to 9 inches thick, has hue of 10YR or 5Y, value of 2 or 3, and chroma of 1 or 2 moist.
The Btg horizon has value of 4 or 5 and chroma of 1 or 2 moist. It is 60 to 70 percent clay.
COMPETING SERIES: These are the similar Coweeman and Natal series. Coweeman and Natal soils are in a fine family. In addition, Coweeman soils have a xeric moisture regime.
GEOGRAPHIC SETTING: Viola soils are in concave areas on terraces at elevations from 300 to 600 feet. They developed in old sediments mainly from basaltic and andesitic rocks. The climate is characterized by warm, dry summers and cool, wet winters. The mean January temperature is 38 degrees F and in July it is 64 degrees F. The mean annual temperature is about 51 degrees F. The average frost-free season is 165 to 180 days. The average annual precipitation is 45 to 65 inches.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Godfrey, Mart, Olympic, Seaquest, Snohomish, and Speelyai soils. Godfrey soils are fine textured, lack an argillic horizon, and are on flood plains. Mart, Olympic, and Seaquest soils are well drained and have a xeric moisture regime. Snohomish soils lack an argillic horizon and have organic layers in the particle-size control section.
DRAINAGE AND PERMEABILITY: Poorly drained, very slow runoff, and very slow permeability. This soil has a high water table at 0-to-1 foot during the winter and spring unless drained.
USE AND VEGETATION: Principal use is timber production. Cleared areas are used for hay and pasture. The native vegetation is red alder, western redcedar, Oregon ash, Douglas-fir, black cottonwood, and western hemlock with an understory of salal, willow, sedges, rushes, wildrose, and western brackenfern.
DISTRIBUTION AND EXTENT: Southwestern Washington. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Clackamas County, Oregon, 1921.
REMARKS: This soil was called Coweeman silty clay loam, dark variant in the 1974 Soil Survey of the Cowlitz Area, Washington. Diagnostic horizons and features recognized in this pedon are an ochric epipedon that meets all requirements for an umbic epipedon except thickness from the surface to 9 inches, and an argillic horizon from 9 to 60 inches.