LOCATION ST. HELENS WAEstablished Series
TAXONOMIC CLASS: Ashy over sandy or sandy-skeletal, glassy over mixed, frigid Typic Udivitrands
TYPICAL PEDON: St. Helens sandy loam - under a coniferous forest on a 5 percent southeast-facing slope at 2,130 feet. (Colors are for moist soil unless otherwise noted. All textures are apparent field textures.)
Oe--1 inch to 0; loose partially decomposed organic litter, composed of needles, leaves, twigs, cones and bark.
E--0 to 2 inches; dark grayish brown (10YR 4/2) sandy loam (volcanic ash), gray (10YR 6/1) dry; weak fine granular structure; soft, friable, nonsticky and nonplastic; many very fine and common fine and medium roots; many very fine irregular pores; moderately acid (pH 5.8); abrupt smooth boundary. (1 to 3 inches thick)
Bw1--2 to 4 inches; very dark brown (10YR 2/2) sandy loam (volcanic ash), very dark grayish brown (10YR 3/2) dry; weak fine granular structure; soft, friable, nonsticky and nonplastic; many very fine and common fine and medium roots; many very fine irregular pores; moderately acid (pH 6.0); abrupt smooth boundary. (2 to 4 inches thick)
Bw2--4 to 6 inches; very dark grayish brown (10YR 3/2) loamy sand (volcanic ash), light grayish brown (10YR 6/2) dry; weak fine subangular blocky structure; soft, friable, nonsticky and nonplastic; many very fine and common fine and medium roots; many very fine irregular pores; 10 percent pumice; moderately acid (pH 6.0); abrupt smooth boundary. (2 to 3 inches thick)
2Bw3--6 to 9 inches; light brownish gray (10YR 6/2) extremely paragravelly loamy sand (cinders and volcanic ash); light gray (10YR 7/2) dry; with stains of light yellowish brown (10Y 6/4); single grain; loose; many very fine roots; many medium and coarse irregular pores; 80 percent rounded and subangular pumice fragments (2 to 5mm in diameter), 5 percent pebbles; slightly acid (pH 6.4); abrupt smooth boundary. (3 to 4 inches thick)
3Bw4--9 to 18 inches; dark brown (10YR 3/3) sandy loam (volcanic ash), pale brown (10YR 6/3) dry; moderate fine and medium subangular blocky structure; soft, friable, nonsticky, slightly plastic and weakly smeary; few fine and common medium roots; many very fine irregular pores; 10 percent.
4BC--18 to 28 inches; dark grayish brown (10YR 4/2) sand (volcanic ash), light brownish gray (10YR 6/2) dry; single grain; loose; few medium and fine roots; many fine and medium irregular pores; 10 percent angular and subangular pumice fragments (2 to 10mm in diameter); slightly acid (pH 6.4); gradual smooth boundary. (5 to 12 inches thick)
5C--28 to 60 inches; dark grayish brown (10YR 4/2) very gravelly coarse sand, gray (10YR 6/1) dry; massive; hard, firm, nonsticky and nonplastic; many medium and coarse irregular pores; 50 percent pebbles and 10 percent cobbles; slightly acid (pH 6.2)
TYPE LOCATION: Skamania County, Washington; near Pine Creek, 1,200 feet south and 2,100 feet east of the northwest corner of sec. 4, T. 7 N., R. 6 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature is 45 to 47 degrees F. These soils are dry for less then 45 consecutive days in the moisture control section. Depth to the sandy-skeletal layer is 20 to 35 inches. The upper 20 to 35 inches has greater than 60 percent by weight volcanic ash and pumice. The E horizon has value of 3 or 4 moist, 5 or 6 dry; and chroma of 1 or 2 moist and dry.
The Bw horizon hs value of 2 or 3 moist, 3 to 6 dry, and chroma of 1 to 3 moist or dry. Pumice fragments average from 5 to 15 percent. It has 10 to 12 percent 15-bar moisture (dry).
The 2Bw horizon has 60 to 85 percent pumice fragments and 5 to 15 percent pebbles. Iron stains have hue of 10YR or 7.5YR, value of 5 or 6.
The 3Bw horizon has hue of 10YR or 7.5YR, values of 3 or 4 moist. It is sandy loam or fine sandy loam. Some pedons have lenses of scoria. It has 12 to 15 percent 15-bar moisture (dry).
The 4BC horizon has 5 to 15 percent pumice. It is sand or loamy sand. It has 10 to 12 percent 15-bar moisture (dry).
The 5C horizon has 30 to 50 percent pebbles and 5 to 15 percent cobbles. It is very gravelly or extremely gravelly.
COMPETING SERIES: There are no competing series. Similar series are the Bannel, Nevine, Parmenter, Pinchot, Rathdrum, Thow, and Zynbar soils. Bannel and Rathdrum soils are ashy throughout the particle-size control section. Nevine soils are ashy over loamy-skeletal. Parmenter, Rathdrum, and Thow soils have a xeric moisture regime. Pinchot soils are mesic. Zynbar soils are medial.
GEOGRAPHIC SETTING: The St. Helens soils are on terraces at elevations of 1,600 to 2,800 feet. Slopes are 0 to 30 percent. St. Helens soils formed in layers of aerially deposited pumice and volcanic ash over pyroclastic flows and lahars. Beginning from the surface of the mineral soil the stratigraphy of pyroclastic material represented in a typical profile includes: (1) fresh ash from the 176-year-old "Layer T", (2) pumice from the 400-year- old "Layer W", (3) and (4) ash, pumice, and scoria from the 2,500-year-old "B set", and (5) pyroclastic flows from the 3,000-year-old "P set." The climate is characterized by warm, moist summers and cold, wet winters. Average annual precipitation is 125 to 135 inches including considerable snowfall. Mean annual air temperature is 43 to 45 degrees F. The frost-free season is 90 to 110 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Bannel, Forsyth, Polepatch, Shoestring, and the competing Pinchot soils. Bannel soils are ashy and have less than 35 percent rock fragments in the control section. Forsyth and Polepatch soils are sandy-skeletal. Polepatch and Shoestring soils are cryic.
DRAINAGE AND PERMEABILITY: Well drained; slow to medium runoff, moderate permeability above the VC horizon and rapid below.
USE AND VEGETATION: Used mainly for timber production, recreation, wildlife habitat and watershed. Overstory vegetation includes Douglas- fir, western
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, 1947.
REMARKS: Diagnostic horizons and features recognized in this pedon are an ochric epipedon from the mineral surface to 9 inches, and a cambic horizon from 9 to 28 inches; sandy-skeletal material is at 28 inches. The particle-size control section is from the mineral soil surface to 40 inches and has three contrasting particle-size classes; from 0 to 6 inches qualifying as ashy; from 6 to 9 inches qualifying as ashy-pumiceous; 9 to 18 inches qualifying as medial; from 18 to 28 inches qualifying as ashy; and from 28 to 40 inches qualifying as sandy-skeletal. The particle-size class was based on the contrasting ashy layer (4BC horizon) over the sandy or sandy-skeletal layer (5C horizon). Classification changes 6/98 based on 1998 Keys to Soil Taxonomy.