LOCATION ELKPRAIRIE WAEstablished Series
TAXONOMIC CLASS: Ashy over medial, glassy over amorphic, acid Vitrandic Cryorthents
TYPICAL PEDON: Elkprairie loamy sand - on a 3 percent southeast-facing slope at an elevation of 4,500 feet. (Colors are for moist soil unless otherwise stated)
C1--0 to 6 inches; dark gray (5Y 4/1) loamy sand, light gray (5Y 6/1) dry; massive; soft, friable, nonsticky and nonplastic; very strongly acid (pH 4.6); abrupt smooth boundary. (4 to 7 inches thick)
C2--6 to 11 inches; dark gray (5Y 4/1) paragravelly sand, light gray (5Y 4/1) dry; single grain; loose; 20 percent pumice fragments; very strongly acid (pH 4.6); gradual wavy boundary. (4 to 6 inches thick)
C3--11 to 17 inches; dark gray (5Y 4/1) paragravelly coarse sand, olive gray (54Y 5/2) dry, single grain; loose; 20 percent pumice fragments; very strongly acid (pH 4.6); gradual wavy boundary. (5 to 7 inches thick)
C4--17 to 23 inches; very dark gray (10YR 3/1) very paragravelly loamy sand, gray (10YR 5/1) dry; single grain; loose; 30 percent fine pumice fragments, 10 percent pebbles; very strongly acid (pH 4.6); abrupt smooth boundary. (4 to 6 inches thick)
2Ab--23 to 26 inches; very dark brown (10YR 2/2) fine sandy loam, very dark grayish brown (10YR 3/2) dry; weak fine subangular blocky structure; soft, friable, nonsticky and nonplastic; common very fine and fine tubular pores; extremely acid (pH 4.4); gradual wavy boundary. (3 to 5 inches thick.
2Bwb1--26 to 29 inches; brown (10YR 4/3) paragravelly loam, yellowish brown (10YR 5/6) dry; weak fine subangular blocky structure; soft, friable, nonsticky and nonplastic and weakly smeary; common very fine and fine tubular pores; 20 percent pumice fragments; NaF pH 11.5; very strongly acid (pH 4.6); gradual wavy boundary. (3 to 7 inches thick)
2Bwb2--29 to 36 inches; reddish yellow (7.5YR 6/8) paragravelly loam, yellow (10YR 7/8) dry; common medium distinct yellowish brown (10YR 5/4) mottles, yellowish brown (10YR 5/6) dry; weak medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic; 20 percent pumice fragment; NaF pH 11.5; very strongly acid (pH 4.8); gradual wavy boundary. (7 to 9 inches thick)
2Bwb3--36 to 60 inches; yellowish brown (10YR 5/8) loam, yellow (10YR 8/8) dry; common medium distinct gray (5Y 5/1) mottles, light gray (5Y 7/1) dry; weak medium subangular blocky structure; soft, friable, slightly sticky and slightly plastic and weakly smeary; 10 percent pumice fragments; NaF pH 11.0; moderately acid (pH 5.8)
TYPE LOCATION: Cowlitz County, Washington, about 23 miles east of Toutle, 2,500 feet south, 1,000 feet west of the northeast corner of sec. 25, T. 10 N., R. 4 E.
RANGE IN CHARACTERISTICS: Average annual soil temperature ranges from 42 to 45 degrees F. The upper part of the control section ranges from 10 to 30 percent pumice fragments. Depth to the buried soil ranges from 20 to 35 inches. The particle-size control section is 60 to 80 percent volcanic glass and glass aggregates. It is very strongly acid to moderately acid. Depth to medial material ranges from 36 to 50 inches.
The C horizon has hue of 2.5Y or 5Y, value of 3 or 4 moist, 4 to 7 dry, and chroma of 1 or 2 moist or dry. Textures range from loamy sand to sand, with 10 to 30 percent pumice fragments.
The 2Ab horizon has value of 2 or 3 moist, 3 or 4 dry and chroma of 1 or 2 moist or dry. Texture is fine sandy loam or sandy loam.
The 2Bwb horizon has hue of 7.5YR or 10YR, value of 4 to 6 moist, 5 to 8 dry, and chroma of 3 to 8 moist or dry. Mottles are none to common and have hues of 10YR to 5Y, value of 5 to 7 moist or dry and chroma of 1 to 6 moist or dry. Texture is loam or sandy loam. It is 5 to 35 percent coarse fragments including 5 to 25 percent pumice fragments and 0 to 25 percent rock fragments.
COMPETING SERIES: No other soils in this family. Kweo, Lapine, Maklak, and Panhandle are in a cindery family. Kweo and Lapine soils also have a xeric moisture regime and an A horizon. Maklak soils have appreciable amounts of scoriaous pebbles in the particle-size control section and have a weakly developed solum.
GEOGRAPHIC SETTING: Elkprairie soils are on terraces and hillsides at elevations of 2,600 to 4,700 feet. Slopes range from 0 to 30 percent. Elkprairie soils formed in fresh volcanic ash and pumice over older soils formed from volcanic ash and pumice. The upper 20 to 35 inches of the profile is ejecta from the 1980 eruption of Mt. St. Helens. The climate is characterized by cool, moist summers and cold, wet winters. The average annual precipitation is about 120 to 135 inches including snow cover from November to June. The average January temperature is about 25 degrees F., the average July temperature is about 53 degrees F, and the average annual temperature is about 38 to 42 degrees F. The growing season is 75 to 95 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the overblown phases of Lonestar, Polepatch, and Vanson soils. These soils have a mantle of 1980 St. Helens ash less than 20 inches thick. In addition, Lonestar soils have a spodic horizon. Polepatch soils are sandy-skeletal, and are somewhat excessively drained. Vanson soils are 35 to 70 percent angular and subangular hard pebbles and cobbles in the lower part of the control section.
DRAINAGE AND PERMEABILITY: Well drained; slow or medium runoff; moderate permeability.
USE AND VEGETATION: Used for watershed and recreation. Vegetation is absent to very sparce. The soil is assumed to be able to support lodgepole pine.
DISTRIBUTION AND EXTENT: Near Mt. St. Helens in northern Skamania and eastern Cowlitz Counties, Washington. The series is of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Skamania County, Washington, 1987.
REMARKS: This pedon lacks diagnostic horizons. The upper 23 inches is tephra from the 1980 eruption of Mt. St. Helens. The buried soil at 23 to 60 inches is older tephra from Mt. St. Helens. Andic properties are from 23 to 60 inches. Vitrandic feature from 23 to 30 inches having an estimated volcanic glass content of greater than 60 percent and acid-oxalate extractable aluminum plus one-half iron of 1.0 to 2.0 percent.
Classification changed 6/98 based on 1998 Keys to Soil Taxonomy.