LOCATION OLOTANIA AS PBEstablished Series
TAXONOMIC CLASS: Medial, amorphic, isohyperthermic Hydric Hapludands
TYPICAL PEDON: Olotania silty clay loam - on a 34 percent slope in a tropical rain forest. When described the soil was moist throughout. (Colors are for moist soil unless otherwise stated. Textures are apparent field textures.)
A--0 to 8 inches; dark brown (7.5YR 3/2) silty clay loam, dark brown (7.5YR 3/2) dry; weak fine and medium subangular blocky structure; extremely hard, friable, sticky and slightly plastic, weakly smeary; many roots; many very fine and common fine pores; few weathered cinders; high in organic matter; moderately acid (pH 6.0); clear smooth boundary. (6 to 9 inches thick)
Bw--8 to 25 inches; dark yellowish brown (10YR 3/4) silty clay loam, dark yellowish brown (10YR 3/4) dry; weak medium subangular blocky structure; very hard, friable, sticky and slightly plastic; moderately smeary; many roots; many very fine and few fine pores; 20 percent highly weathered cinders that crush easily; slightly acid (pH 6.5); abrupt smooth boundary. (14 to 32 inches thick)
2C--25 to 60 inches; stratified layers of weathered cinders that have variegated colors of black (10YR 2/1), brown (10YR 4/3), and dark reddish brown (2.5YR 3/4) clay loam, sandy loam and silty clay loam, dark yellowish brown (10YR 3/4), brownish yellow (10YR 6/6) and reddish yellow (7.5YR 6/6) dry; massive in places and weak medium subangular blocky structure in other places; very hard, friable, sticky and slightly plastic; few roots; few fine and very fine pores; slightly acid (pH 6.4).
TYPE LOCATION: Ta`u Island, American Samoa; about 1/2 mile west northwest of Olomanu Crater; lat. 14 degrees 14 minutes 31 seconds S. and long. 169 degrees 29 minutes 25 seconds W.
RANGE IN CHARACTERISTICS: The solum is 20 to 40 inches thick. It is slightly acid to strongly acid in the solum and slightly acid or neutral in the C horizon.
The A horizon has hue of 7.5YR or 10YR, value of 2 or 3, and chroma of 2 or 3 moist and dry. It has weak to moderate subangular blocky structure.
The B horizon has hue of 7.5YR or 10YR, value of 3 or 4 moist, 3 through 5 dry, and chroma of 3 or 4 moist, 3 through 6 dry. It is slightly smeary to moderately smeary. It dries irreversibly to dark, angular, very hard, gravel-size aggregates.
The C horizon has variegated colors with hue of 2.5YR through 10YR, value of 2 through 4 moist, 3 through 7 dry, and chroma of 1 through 4 moist, 4 through 6 dry.
COMPETING SERIES: These are the Hana and Hilo soils. Hana soils have strong structure in the A horizon and are underlain with cinders and Aa lava at depths of 27 to 40 inches. Hilo soils have prismatic structure in the B horizon.
GEOGRAPHIC SETTING: Olotania soils are on moderately steep and steep mountainsides. Slope is dominantly 15 to 40 percent, and as steep as 70 percent along drainageways and on ridges, and cinder cones. These soils formed in volcanic ash and cinders. Elevation is 900 to 3,000 feet. The mean annual rainfall is 200 to 300 inches, and the mean annual temperature is 74 to 78 degrees F. Fog and cloud cover are common.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Pavaiai soils which commonly occur downslope of the Olotania soils. Pavaiai soils are medial-skeletal.
DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately rapid permeability.
USE AND VEGETATION: Most areas are in natural tropical rain forest vegetation of broadleaf trees and an understory of tree ferns, ground ferns, and shrubs. The area is not easily accessible. Trails become overgrown in a short time. In the lower elevations coconuts were grown in the past.
DISTRIBUTION AND EXTENT: Island of Ta`u. The soils of this series are of small extent, about 5000 acres.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Davis, California
SERIES ESTABLISHED: American Samoa, 1982.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - From the surface to a depth of 8 inches (20 centimeters) (The A horizon).
Cambic horizon - from 8 to 25 inches (20 to 64 centimeters (The Bw horizon)
Andic soil properties - 0 to 60 inches
Perudic moisture regime
Taxonomic Version: Second edition Soil Taxonomy, 1999.
ADDITIONAL DATA: This pedon number S81AS 602-056 was sampled as Olomanu and analysis was performed by the SCS National Soil Survey Laboratory in 1981.