LOCATION PACIFIC MESA CA
Established Series
Rev: LJL/ET
12/2015
PACIFIC MESA SERIES
The Pacific Mesa series consists of shallow to bedrock, well drained soils that formed in residuum and colluvium from andesite and basalt. Pacific Mesa soils are on mountains and slopes range from 8 to 50 percent. The mean annual precipitation is about 4 inches and the mean annual air temperature is about 66 degrees F.
TAXONOMIC CLASS: Loamy-skeletal, mixed, superactive, thermic Lithic Haplocambids
TYPICAL PEDON: Pacific Mesa extremely gravelly sandy loam on a west-facing, smooth, 28 percent slope at an elevation of 2,285 feet. (Colors are for dry soil unless otherwise noted.) The surface is covered by approximately 80 percent gravel, 5 cobbles and 3 stones.
A--0 to 2 inches; light yellowish brown (10YR 6/4) extremely gravelly sandy loam, dark yellowish brown (10YR 4/4) moist; moderate fine subangular blocky structure; soft, very friable, slightly sticky and nonplastic; few very fine and fine roots; common very fine and few fine interstitial and tubular pores; 70 percent gravel, 5 percent cobbles and 2 percent stones; slightly effervescent; slightly alkaline (pH 7.8); abrupt smooth boundary. (1 to 3 inches thick)
Bkq1--2 to 8 inches; light brown (7.5YR 6/4) extremely gravelly sandy loam, brown (7.5YR 4/4) moist; weak medium subangular blocky structure; soft, very friable, slightly sticky and nonplastic; common very fine, few fine and medium roots; common very fine interstitial pores and few fine interstitial and tubular; 70 percent gravel, 3 percent cobbles and trace of stones; few thin lime and silica coats on undersides of rock fragments; strongly effervescent; moderately alkaline (pH 8.0); clear smooth boundary.
Bkq2--8 to 18 inches; light brown (7.5YR 6/4) extremely gravelly sandy loam, brown (7.5YR 4/4) moist; massive; soft, very friable, slightly sticky and nonplastic; common very fine, few fine and medium roots; few very fine and fine interstitial pores and few fine tubular; 2 percent very fine soft masses of calcium carbonate; 70 percent gravel, 3 percent cobbles and trace of stones; few thin lime and silica coats on undersides of rock fragments; violently effervescent; moderately alkaline (pH 8.2); abrupt wavy boundary. (Combined thickness of the Bkq horizons is 8 to 18 inches)
R--18 inches; hard unweathered andesite bedrock.
TYPE LOCATION: San Bernardino County, California; about 9 1/2 miles south of Ludlow, California in the Bullion Mountains; approximately 3/4 of a mile south-southeast of Pacific Mesa; 1400 feet north and 1800 feet east of the southwest corner of section 28, T. 6 N., R. 8 E.; 34 degrees, 34 minutes, 44.6 seconds north latitude and 116 degrees, 09 minutes, 24.6 seconds west longitude; Morgans Well quadrangle; UTM 11S, 0577335e 3826489n; NAS-C.
RANGE IN CHARACTERISTICS:
Soil moisture - usually dry, moist in some part for short periods during winter and early spring and for 10 to 20 days cumulative between July and October following convection storms. The soils have a Typic-Aridic moisture regime.
Soil temperature: 59 to 71 degrees F.
Depth to lithic contact: 10 to 20 inches.
Organic matter: 0 to 0.5 percent.
Control section - Rock fragments: 60 to 85 percent, mainly gravel. Cobbles and stones dominate in some pedons.
Clay content: 5 to 12 percent.
Reaction: Slightly alkaline or moderately alkaline.
A horizon - Chroma: 3 or 4.
Consistence: Soft or slightly hard, nonsticky or slightly sticky.
Effervescence: Slightly effervescent or strongly effervescent.
Calcium carbonate equivalence: 1 to 5 percent.
Electrical conductivity: 0 to 2 dS/m.
Sodium adsorption ratio: 0 to 4.
Bkq horizons - Hue: 7.5YR or 10YR.
Chroma: 3 or 4.
Consistence: Nonsticky or slightly sticky.
Effervescence: Strongly effervescent or violently effervescent.
Calcium carbonate equivalence: 1 to 5 percent.
Electrical conductivity: 0 to 2 dS/m.
Sodium adsorption ratio: 0 to 4.
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Pacific Mesa soils are on mountains. Slopes range from 8 to 50 percent. These soils formed in residuum and colluvium from andesite and basalt. Elevations are 2000 to 4600 feet. The climate is arid with hot, dry summers and warm, moist winters. The mean annual precipitation is 3 to 7 inches; mean annual air temperature is 57 to 69 degrees F., and the frost-free season is 180 to 300 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are
Noble Pass and
Sunrock soils. Noble Pass soils are less than 10 inches deep to bedrock. Sunrock soils have a mean annual soil temperature of 72 to 80 degrees F. and lack a cambic horizon.
DRAINAGE AND PERMEABILITY: Well drained; very high runoff; moderately rapid permeability.
USE AND VEGETATION: Pacific Mesa soils are used for military exercises and wildlife habitat. The present vegetation is mainly creosotebush and white bursage.
DISTRIBUTION AND EXTENT: Mojave Desert of southeastern California, U.S.A. MLRA 30. These soils are of small extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: PHOENIX, ARIZONA
SERIES ESTABLISHED: San Bernardino County, California, Marine Corps Air/Ground Combat Center Soil Survey Area, 2000. The name is from Pacific Mesa located in the Bullion Mountains.
REMARKS: Diagnostic horizons and features recognized in the profile are:
1. Ochric epipedon -- 0 to 2 inches (A horizon).
2. Cambic horizon - 2 to 18 inches (Bkq1 and Bkq2 horizons).
3. Lithic contact -- 18 inches (R horizon).
4. Particle-size control section -- 10 to 18 inches (Part of the Bkq2 horizon).
Responsibility for this series was transferred from Davis to Phoenix 12/2015. The last revision to the series was 2/2001. ET
National Cooperative Soil Survey
U.S.A.