LOCATION HARTPEAK                CA

Established Series
Rev: LJL/CAH/ET
04/2015

HARTPEAK SERIES

The Hartpeak series consists of moderately deep, well drained soils that formed in residuum and colluvium from mixed volcanic sources. Hartpeak soils are on backslopes of hills. Slope ranges from 15 to 50 percent. The mean annual precipitation is about 200 millimeters and the mean annual temperature is about 14 degrees C. The frost-free season is 210 to 240 days.

TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Ustic Haplargids

TYPICAL PEDON: Hartpeak extremely cobbly loam, on a 26 percent slope under desert rangeland at an elevation of 1411 meters. When described the soil was dry throughout. (Colors are for dry soil unless otherwise noted). The soil surface is covered by approximately 50 percent gravel, 25 percent cobbles, 3 percent stones and 1 percent boulders.

A--0 to 6 centimeters (0 to 2 inches); brown (10YR 5/3) extremely cobbly loam, dark brown (10YR 3/3) moist; moderate medium and coarse subangular blocky structure; slightly hard, very friable, slightly sticky and slightly plastic; common very fine roots; many very fine, few fine and medium vescular and tubular pores; 5 percent fine gravel and 35 percent medium and coarse gravel, 25 percent cobbles and 3 percent stones; slightly alkaline (pH 7.6); abrupt smooth boundary. (4 to 6 centimeters thick)

Bw--6 to 16 centimeters (2 to 6 inches); brown (10YR 5/3) very cobbly loam, dark brown (10YR 3/3) moist; moderate medium subangular blocky structure; moderately hard, very friable, slightly sticky and slightly plastic; common very fine, few fine and medium roots; many very fine and few fine tubular pores; 5 percent fine gravel and 20 percent medium and coarse gravel, 20 percent cobbles and 1 percent stones; slightly alkaline (pH 7.6); clear wavy boundary. (0 to 10 centimeters thick)

Btk1--16 to 25 centimeters (6 to 10 inches); brown (7.5YR 4/4) very cobbly loam, dark brown (7.5YR 3/4) moist; moderate medium subangular blocky structure; moderately hard, very friable, slightly sticky and slightly plastic; common very fine and few fine roots; many very fine and few fine tubular pores; 30 percent faint clay films on all faces of peds, surfaces of pores and around rock fragments; 40 percent prominent, white (10YR 8/1), calcium carbonate coats on bottom of rock fragments; 5 percent fine gravel and 20 percent medium and coarse gravel, 20 percent cobbles and 1 percent stones; slightly alkaline (pH 7.8); clear wavy boundary.

Btk2--25 to 37 centimeters (10 to 15 inches); brown (7.5YR 4/4) very cobbly clay loam, dark brown (7.5YR 3/4) moist; moderate medium angular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; many very fine and few fine tubular pores; 70 percent distinct clay films on all faces of peds, surfaces of pores and rock fragments; 40 percent prominent, white (10YR 8/1), calcium carbonate coats on bottom of rock fragments; 5 percent fine gravel and 20 percent medium and coarse gravel, 20 percent cobbles and 1 percent stones; moderately alkaline (pH 8.0); clear wavy boundary.

Btkq--37 to 55 centimeters (15 to 22 inches); brown (7.5YR 4/4) very cobbly clay loam, brown (7.5YR 4/4) moist; moderate medium angular blocky structure; hard, friable, moderately sticky and moderately plastic; common very fine roots; many very fine and few fine tubular pores; 70 percent distinct clay films on all faces of peds, surfaces of pores and rock fragments; 40 percent prominent, white (10YR 8/1), calcium carbonate coats on bottom of rock fragments; 3 percent prominent, yellowish brown (10YR 5/6) silica coats on bottom of rock fragments; 5 percent fine gravel and 20 percent medium and coarse gravel, 20 percent cobbles and 1 percent stones; slightly effervescent; moderately alkaline (pH 8.0); very abrupt irregular boundary. (The combined thickness of the Btk horizons is 30 to 60 centimeters.)

R--55 centimeters (22 inches); welded volcanic tuff bedrock.

TYPE LOCATION: San Bernardino County, California; about 23 kilometers southwest of Searchlight, Nevada in the Castle Mountains; approximately 3 kilometers west and 1 kilometer south of Hart Peak; about 335 meters north and 70 meters west of the southeast corner of section 35, T. 15 N., R. 17 E.; USGS Hart Peak, California-Nevada 7.5 minute topographic quadrangle; 35 degrees, 20 minutes, 2.5 seconds north latitude and 115 degrees, 6 minutes, 37.4 seconds west longitude; UTM 11S, 671736e and 3911726n; (DATUM: NAD83).

RANGE IN CHARACTERISTICS:

Soil moisture - Usually dry, moist in some part from December to March and intermittently moist for 10 to 20 days during July to October following summer convection storms; aridic moisture regime bordering on ustic.

Soil temperature: 15 to 18 degrees C.

Depth to argillic horizon: 4 to 20 centimeters.
Depth to lithic contact: 50 to 75 centimeters.

Control section - Rock fragments: 35 to 65 percent with 15 to 30 percent gravel, 15 to 30 percent cobbles, and 0 to 7 percent stones.
Clay content: Averages 25 to 35 percent.

A horizon
Texture of the fine earth fraction: Loam or silt loam.
Rock fragments: 50 to 65 percent, 30 to 40 gravel, 10 to 25 percent cobbles and 1 to 25 percent stones.
Reaction: Neutral or slightly alkaline.

Bw horizon
Texture of the fine earth fraction: Loam or silt loam.
Structure: Fine or medium.
Rock fragments: 35 to 65 percent, 15 to 30 percent gravel, 15 to 30 percent cobbles, and 0 to 7 percent stones.
Reaction: Neutral or slightly alkaline.
Other features: Some pedons have non-diagnostic clay films.

Btk and/or Btkq horizons
Hue: 10YR or 7.5YR.
Value: 4 through 6 dry, 3 through 5 moist.
Chroma: 3 or 4, dry or moist.
Texture of the fine earth fraction: Clay loam or loam.
Clay content: Averages 25 to 35 percent, ranges from 18 to 35 percent.
Calcium carbonate equivalence of the fine earth: 0 to 1 percent.

Structure: Weak through strong, fine or medium, angular blocky or subangular blocky.
Consistence: Moderately hard through very hard, very friable or friable, slightly sticky or moderately sticky, and slightly plastic or moderately plastic.
Rock fragments: 35 to 65 percent with 15 to 30 percent gravel, 15 to 30 percent cobbles, and 0 to 7 percent stones.
Clay content: Averages 25 to 35 percent, ranges from 18 to 35 percent.
Reaction: Slightly alkaline or moderately alkaline.
Other features: Some pedons lack secondary calcium carbonate and/or silica.

COMPETING SERIES: These are the Caralampi (AZ), Coxwell (NM), Holliday (NM), Hoppswell (NV), Hyrhy (AZ), Maloy (AZ) and Monza (NM) series. Caralampi, Holliday, Hoppswell, Maloy and Monza soils have profiles deeper than 60 inches. Coxwell soils have weathered granitic bedrock at 20 to 40 inches. Hyrhy soils have a soil moisture control section that is moist for 30 to 45 days between July and September and have a calcium carbonate equivalent of 10 to 15 percent.

GEOGRAPHIC SETTING: Hartpeak soils are on backslopes of hills. Slope ranges from 15 to 50 percent. These soils formed in residuum and colluvium from mixed volcanic sources. Elevations are 1,300 to 1,675 meters. The climate is semiarid with cool, moist winters and warm, intermittently moist summers. The mean annual precipitation is 180 to 230 millimeters; mean annual air temperature is 13 to 16 degrees C., and the frost-free season is 180 to 240 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are Highland, Hoppswell, Straycow and Ustidur soils. Highland soils occur on lower backslopes of hills and are moderately deep to bedrock. Hoppswell soils occur on smooth fan remnants and are very deep. Straycow soils occur on hills of igneous parent material and are shallow to bedrock. Ustidur soils occur on ballenas and are shallow to a duripan.

DRAINAGE AND PERMEABILITY: Well drained; very high runoff; moderately slow permeability above the bedrock.

USE AND VEGETATION: These soils are used for rangeland and wildlife habitat. The present vegetation is mainly big galleta, galleta, banana yucca, desert needlegrass, Anderson wolfberry, black grama and catci. This is a burned blackbrush site. The size of the survey area did not allow for a note in a non-burned area.

DISTRIBUTION AND EXTENT: Mojave Desert of southeastern California; MLRA 30. These soils are not extensive.

MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: PHOENIX, ARIZONA

SERIES ESTABLISHED: San Bernardino County, California; Crescent Peak Grazing Allotment, part of the Mojave National Preserve Soil Survey Area, 2007. The name is coined from Hart Peak located in the Castle Mountains.

REMARKS: Diagnostic horizons and features recognized in the profile are:
1. Ochric epipedon - 0 to 16 centimeters (0 to 6 inches). (A and Bw horizons)
2. Argillic horizon - 16 to 55 centimeters (6 to 22 inches). (Btk1, Btk2 and Btkq horizons)
3. Lithic contact - 55 centimeters (22 inches). (R horizon)
4. Particle-size control section - 16 to 55 centimeters (6 to 22 inches). (Btk1, Btk2 and Btkq horizons)

Responsibility for this series was transferred from Davis to Phoenix 4/2015. The last revision to the series was 5/2007. ET

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National Cooperative Soil Survey
U.S.A.