LOCATION IRON MOUNTAIN CAEstablished Series
TAXONOMIC CLASS: Loamy, mixed, superactive, mesic Lithic Haploxerolls
TYPICAL PEDON: Iron Mountain gravelly sandy loam - range land. (Colors are for dry soil unless otherwise stated)
Al--O to 9 inches; dark grayish brown (10YR 4/2) gravelly sandy loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; slightly hard, friable; common very fine roots; many very fine pores; about 25 percent subrounded gravel; slightly acid; abrupt irregular boundary. (5 to 20 inches thick)
R--9 inches; hard volcanic breccia which is impervious to both roots and water.
TYPE LOCATION: Tehama County, California; at "The Narrows" just east of the junction of Ponderosa Way and the Lassen Trail in the SE1/4 of sec. 20, T.27N., R.3E.
RANGE IN CHARACTERISTICS: Depth to bedrock ranges from 5 to 20 inches. The mean annual soil temperature above the bedrock ranges from 47 degrees to 59 degrees F. Some part of the soil between 5 inches and the lithic contact is usually moist all the time from October until late May or June and is dry the rest of the time. Rock fragments are usually about 20 to 25 percent but range from 5 to 35 percent throughout the profile. Base saturation ranges from 50 to 75 percent. The soil is influenced but not dominated by amorphous material.
The A horizon has dry colors of 10YR 4/1, 5/1; 3/2, 4/2, 5/2; 3/3, 4/3 or 5/3. Moist colors are 10YR 2/1, 3/1, 2/2 3/2 or 3/3. Organic matter ranges from 2 to 6 percent. It is sandy loam or loam and may be gravelly, cobbly or stony. It is moderately acid or slightly acid.
In profiles more than 10 inches deep a C horizon may be present. It has dry colors of 10YR 6/3, 6/4 or 5/2. It is moderately acid or strongly acid and is sandy loam with cobbles and pebbles.
COMPETING SERIES: These are the McMullin series, and the Witzel series in another family. McMullin soils are not formed from volcanic rocks and lack Andic properties. Witzel soils are skeletal.
GEOGRAPHIC SETTING: Iron Mountain soils are on gently sloping to very steep mountains and narrow ridge tops at elevations of 1,000 to 6,000 feet. They formed in residuum from volcanic breccia. Outcrops of breccia are common. The climate has cool moist winters and warm dry summers. Annual precipitation ranges from 35 to 70 inches. Mean annual temperature is 52 degrees F. Average January temperature is 35 degrees F., average July temperature is about 70 degrees F. Frost-free season is about 180 to 230 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Aiken, Cohasset, Jiggs, McCarthy and Toomes soils. Aiken and Cohasset soils have sola more than 40 inches thick. Jiggs and McCarthy soils are more than 20 inches deep. Toomes soils lack a mollic epipedon.
DRAINAGE AND PERMEABILITY: Well to somewhat excessively drained; medium to very rapid runoff; moderately rapid permeability above the bedrock.
USE AND VEGETATION: Used for grazing. Natural vegetation is scattered black oak, blue oak, digger pine, manzanita, canyon oak, interior live oak, ceanothus, grasses, and forbs with stunted conifers in places.
DISTRIBUTION AND EXTENT: Cascade Range and Sierra Nevadas of northern California. The soils are moderately extensive.
MLRA OFFICE RESPONSIBLE: Davis, California
SERIES ESTABLISHED: Tehama County, California, 1961.
REMARKS: Iron Mountain soils were formerly classified as medial, mesic Lithic Mollic Vitrandepts. An examination of the available lab. data shows that the 15 bar water to clay ratio is not high enough to qualify for being dominated by amorphous material. Hence not medial. Also bulk densities are not generally any lower than about 1.0 g/cc. Evidence doesn't substantiate having greater than 60 percent vitric material.
The activity class was added to the classification in February of 2003. Competing series were not checked at that time. - ET
OSED scanned by SSQA. Last revised by state on 3/81.