LOCATION FOSS WAEstablished Series
TAXONOMIC CLASS: Medial over loamy-skeletal, amorphic over isotic Typic Vitricryands
TYPICAL PEDON: Foss stony sandy loam - in a clearcut area on a ridge crest. (Colors are for moist soil unless
otherwise noted. All textures are apparent field textures.)
A--0 to 4 inches; very dark brown (10YR 2/2) stony sandy loam, light grayish brown (10YR 6/2) dry; moderate
fine and medium granular structure; soft, very friable, nonsticky and nonplastic; common very fine and fine
roots; 10 percent pebbles; strongly acid (pH 5.4); abrupt smooth boundary. (4 to 6 inches thick)
Bs1--4 to 10 inches; yellowish brown (10YR 54) gravelly sandy loam, light yellowish brown (10YR 6/4) dry;
single grain; loose, nonsticky, nonplastic, weakly smeary; many very fine, fine, medium and coarse roots; 15
percent pebbles; moderately acid (pH 5.6); gradual smooth boundary. (6 to 8 inches thick)
Bs2--10 to 16 inches; strong brown (7.5YR 4/6) gravelly sandy loam, brown (7.5YR 5/4) dry; single grain;
loose, nonsticky, nonplastic, weakly smeary; common very fine, fine and medium roots; 30 percent pebbles,
moderately acid (pH 5.6); gradual irregular boundary. (6 to 10 inches thick)
2Bs3--16 to 32 inches; dark brown (7.5YR 3/4) very cobbly silt loam, reddish brown (5YR 4/4) dry; weak
medium subangular blocky structure; soft, very friable, slightly sticky, slightly plastic, moderately smeary;
common fine and medium roots; few thin silt coatings on ped faces and in pores; 35 percent cobbles, 15 percent
pebbles; strongly acid (pH 5.4); clear wavy boundary. (12 to 18 inches thick)
2BC1--32 to 48 inches; dark reddish brown (5YR 3/3) very gravelly silt loam, brown (7.5YR 5/4) dry;
moderate medium subangular blocky structure; soft, very friable, slightly stick, slightly plastic, moderately
smeary; few fine and medium roots; common thin silt coatings on ped faces and in pores; 45 percent pebbles, 5
percent cobbles; moderately acid (pH 5.8); abrupt smooth boundary. (14 to 20 inches thick)
2BC2--48 to 60 inches; dark reddish brown (5YR 3/4) very gravelly silt loam, reddish brown (5YR 4/4) dry;
strong fine and medium platy structure; very hard, very firm, slightly sticky, slightly plastic, moderately
smeary; common thin to thick silt coatings on ped faces and in pores; 50 percent pebbles, 5 percent cobbles;
moderately acid (pH 5.6).
TYPE LOCATION: Snoqualmie Pass Area, Pierce County, Washington; 400 feet west and 1,600 feet north of the
southeast corner of sec. 32, T. 19 N., R. 10 E.
RANGE IN CHARACTERISTICS: Mean annual soil temperature ranges from 39 to 44 degrees F. The control section is
loam or silt loam and averages 35 to 55 percent rock fragments that includes 5 to 40 percent cobbles. The soil
is strongly acid or moderately acid throughout.
The A horizon has hue of 7.5YR or 10YR, value of 2 or 3 moist, 5 or 6 dry, and chroma of 2 through 4 moist and
dry. The surface texture is modified by 2 to 10 percent surface stones.
The Bs horizon has hue of 7.5YR or 10YR, value of 4 through 6 moist and dry, and chroma of 4 through 6 moist
and dry. It is sandy loam or loam modified by 15 to 35 percent gravel. In some pedons the upper part is
modified by volcanic ash, pumice and cinders that range from 35 to 70 percent of volume.
The 2Bs horizon has hue of 5YR or 7.5YR, value of 3 or 4 moist, 3 through 5 dry, and chroma of 2 through 4
moist and dry. It is loam or silt loam modified by 35 to 60 percent coarse fragments.
The 2BC horizon is loam or silt loam with 40 to 60 percent coarse fragments. It is hard or very hard when dry
and very firm moist.
COMPETING SERIES: These are the
Almac,
Chiwaukum,
Pinkham, and
Soda series. Almac and Chiwaukum soils have a
xeric moisture regime and are sandy loam or fine sandy loam in the fine- earth fraction of the lower part of the
particle-size control section. Pinkham and Soda soils lack a 2B horizon.
GEOGRAPHIC SETTING: Foss soils are on interior side slopes of cirque basins, broad ridge tops, and benches at
elevations of 3,000 to 5,000 feet. Slopes range from 8 to 65 percent. These soils formed in volcanic ash,
pumice, and residuum and colluvium from andesite. The mean annual precipitation ranges from 70 to 110 inches
with most of it in the form of snow and rain during the winter months. Mean January temperature is 27 degrees
F, the mean July temperature is 58 degrees F, and the mean annual temperature is 42 degrees F. The frost-free
season is 110 to 130 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are
Dobbs,
Haywire,
Littlejohn,
Nagrom,
Nimue,
Pitcher,
Playco, and
Spukwush soils. Dobbs soils have a paralithic contact at a depth of 20 to 40 inches. Haywire soils have a
lithic contact within 20 inches. Littlejohn and Pitcher soils are frigid. Nagrom soils have a lithic contact
at 20 to 40 inches. Playco and Nimue soils are loamy-skeletal. Spukwush soils are ashy over loamy.
DRAINAGE AND PERMEABILITY: Well drained; medium runoff; moderate permeability.
USE AND VEGETATION: Used for timber production. Native vegetation is noble fir, Pacific silver fir, western
hemlock, Douglas-fir, with an understory of common beargrass, evergreen huckleberry, western rattlesnake
plantain, princes pine, and queencup beadlily.
DISTRIBUTION AND EXTENT: West slops of the Cascade Mountains in central Washington. The series is of small
extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Snoqualmie Pass Area, Pierce County, Washington, 1986.
REMARKS: Diagnostic horizons and features recognized in this pedon are an ochric epipedon from the mineral
surface to 4 inches, a spodic horizon from 4 to 32 inches, and a mantle of volcanic ash from the mineral
surface to 16 inches.