LOCATION OBSCURITY WAEstablished Series
TAXONOMIC CLASS: Sandy-skeletal, mixed Typic Cryorthents
TYPICAL PEDON: Obscurity very bouldery sand, on a 10 percent southeast facing slope at an elevation of 3,040 feet. (Colors are for moist soils unless otherwise stated)
C1--0 to 20 inches; gray (10YR 5/1) very bouldery sand, light gray (10YR 7/1) dry; single grain; loose, nonsticky and nonplastic; many coarse irregular pores; 15 percent cobbles, 30 percent pebbles, and 3 percent boulders and stones on the soil surface; moderately acid (pH 5.8); clear wavy boundary. (15 to 25 inches thick)
C2--20 to 60 inches; dark gray (10YR 4/1) very cobbly loamy sand; with thin (2 to 4 inches thick) strata of cindery sand and very cindery loamy sand; light gray (10YR 6/1) dry; single grain; loose, nonsticky and nonplastic; many medium and coarse irregular pores; 5 percent stones, 30 percent cobbles and 25 percent pebbles; 10 percent pumice fragments; medium acid (pH 5.8).
TYPE LOCATION: Skamania County, Washington, about 3.5 miles southeast of Mt. St. Helens: 2,000 feet north and 2,000 feet east of the southwest corner of sec. 19, T. 8 N., R. 6 E.
RANGE IN CHARACTERISTICS: The mean annual soil temperature ranges from 39 to 44 degrees F. The particle-size control section is weakly stratified and averages 35 to 65 coarse fragments and 15 to 50 percent pumice, volcanic glass, and glass aggregates. It is strongly acid or moderately acid. Some profiles contain woody organic debris composed of logs, branches, and bark.
The C1 horizon has hue of 7.5YR to 2.5Y, value of 3 to 7 moist, 5 to 8 dry, and chroma of 0 to 2 moist and dry.
The C2 horizon has hue of 7.5YR to 2.5Y, value of 2 to 5 moist, 3 to 6 dry, and chroma of 0 to 2 moist and dry. It is very cobbly loamy sand or very cobbly sand.
COMPETING SERIES: These are the Alflack, Canlodore, Castlepeak, Chena, Cryomont, Graylock, Howardsville, Legault, Mirror Lake, Nataga, Nizina, Pirapeak, Ragamuffin, Stecum, and Studebaker series. Alflack and Ragamuffin soils are moderately deep to bedrock. Chena, Castlepeak, Howardsville, Graylock, Mirror Lake, Nataga, Nizina, Pirapeak, and Stecum soils lack volcanic ash in the particle-size control section. In addition, Chena soils have a mean annual soil temperature of about 30 degrees F. Graylock soils have a chroma of 3 or 4 in the control section, lack basalt fragments, and have granitic rock fragments in the control section. Mirror Lake soils have 35 to 70 percent quartzite and sandstone fragments in the control section and have a hue of 7.5YR or 5YR in the C horizon. Cryomont soils have an A horizon with more than 60 percent volcanic ash. Legault soils are shallow to bedrock. Stecum soils have a lithic contact within 40 inches of the surface. kCanladore soils have an albic horizon. Studebaker soils lack stratification in the particle-size control section.
GEOGRAPHIC SETTING: The Obscurity soils are on broad fans, low terraces, and along major drainages south of Mt. St. Helens at elevations of 2,800 to 5,500 feet. Obscurity soils formed in mud flow material as the result of melting snow and ice following the May 18, 1980 eruption of Mt. St. Helens. The climate is characterized by warm, moist summers and cold, wet winters. Mean annual precipitation is 125 to 135 inches including considerable snowfall. Average January temperature is 25 degrees F; average July temperature is 58 degrees F; and the mean annual temperature is 42 to 45 degrees F. The frost-free season is 70 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the competing soils and Polepatch, Forsyth, and Shoestring soils. Forsyth soils are frigid. Shoestring soils are medial over sandy or sandy-skeletal and have a spodic horizon.
DRAINAGE AND PERMEABILITY: Somewhat excessively drained; slow runoff; moderately rapid permeability.
USE AND VEGETATION: Some areas are included in the National Geologic Monument. Other areas have been revegetated with grass seedings and willow cuttings. Natural revegetation by fireweed, pearly everlasting vine maple, and red alder has begun.
DISTRIBUTION AND EXTENT: 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, 1984.
REMARKS: This pedon has no diagnostic horizons. The particle-size control section (10 to 40 inches) averages 55 percent rock fragments and 7 percent pumice.