LOCATION TRIGGER                 CA

Established Series
Rev. AFF/GWH/TDC
12/2015

TRIGGER SERIES

The Trigger series consists of shallow, well drained soils that formed in material weathered from hard sedimentary rocks. Trigger soils are on uplands and have slopes of 5 to 50 percent. The mean annual precipitation is about 4 inches (102 millimeters) and the mean annual temperature is about 63 degrees F. (17 degrees C.).

TAXONOMIC CLASS: Loamy, mixed, superactive, calcareous, thermic Lithic Torriorthents

TYPICAL PEDON: Trigger gravelly sandy loam, on a 30 percent slope under creosotebush, Joshua tree, annual forb, and grasses at 2,880 feet (878 meters) elevation. (Colors are for dry soil unless otherwise stated. When described the soil was dry throughout.)

A1--0 to 12 inches (0 to 30 centimeters); very pale brown (10YR 7/3) gravelly sandy loam, brown (10YR 5/3) moist; moderate fine and medium subangular blocky structure; slightly hard, very friable, nonsticky and nonplastic; common very fine roots; few very fine interstitial and tubular pores; 25 percent (1/2 to 3/4 inch or 1 to 2 cm.) pebbles; strongly effervescent, disseminated lime; moderately alkaline (pH 8.0); clear wavy boundary. (10 to 20 inches or 25 to 50 cm. thick)

Cr--12 to 19 inches (30 to 48 centimeters); essentially hard, fractured rock with sandy loam in fracture joints; soil is violently effervescent with disseminated lime; upper 3 or 4 inches (8 or 10 cm.) are slightly weathered in a few places; common very fine roots in fracture joints; no pores noticed; gradual irregular boundary.

R--19 to 24 inches (48 to 61 centimeters); hard blue gray limestone with few seams of pinkish white quartzite.

TYPE LOCATION: San Bernardino County, California; 200 yards (183 meters) southeast of Red Raven Mine; SE1/4 SW1/4 of section 31, T.7N., R.5W.

RANGE IN CHARACTERISTICS: Depth to hard parent rock ranges from 10 to 20 inches (25 to 50 centimeters). The soil moisture control section is usually dry between depths of 10 and 20 inches (25 to 50 centimeters), or to a lithic contact from May to October. The mean annual soil temperature is 62 to 67 degrees F. (16 to 19 degrees C.).

The A horizon is very pale brown or pale brown (10YR 7/3, 6/3, 7/4). Moist colors are dark brown, grayish brown, brown or pale brown (10YR 4/3, 5/2, 5/3, 6/3). This horizon is gravelly sandy loam, gravelly fine sandy loam or gravelly loam and has 15 to 35 percent rock fragments. It is strongly effervescent or violently effervescent with disseminated lime.

Some pedons have a C horizon that is similar in color and texture to the A horizon.

The Cr layer is made up of moderately cemented fractured rock with some strongly to violently effervescent, moderately alkaline, sandy loam or loam soil in fracture joints.

COMPETING SERIES: These are the Courthouse, Delgado and Tidwell series in the same family. Courthouse soils have hue of 5YR through 10YR. (See Remarks) Delgao soils have hue yellower than 10YR. Tidwell soils are intermittently moist in the moisture control section for 30 to 40 days, cumulative, in the summer.

GEOGRAPHIC SETTING: The soils formed in material weathered from hard sedimentary rocks. Trigger soils are at elevations of 2,400 to 3,800 feet (732 to 1159 meters), in a warm arid mediterranean climate. Precipitation is about 3 to 7 inches (76 to 178 millimeters), most of which falls as rain in winter but occasionally as snow. The mean January temperature is about 46 degrees F.(8 degrees C.); the mean July temperature is about 84 degrees F. (29 degrees C.); and the annual temperature is about 61 to 66 degrees F. (16 to 18 degrees C.) The frost free season is about 200 to 250 days.

GEOGRAPHICALLY ASSOCIATED SOILS: These are the Cajon, Mirage and Sparkhule soils. Cajon and Mirage soils lack a lithic contact. Mirage and Sparkhule soils have an argillic horizon.

DRAINAGE AND PERMEABILITY: Well drained; medium to rapid runoff; moderately rapid permeability.

USE AND VEGETATION: Used for wildlife habitat, limited grazing and recreation. Native vegetation is creosotebush, cactus, annual grasses and forbs.

DISTRIBUTION AND EXTENT: Mojave Desert of California. Trigger soils are of small extent.

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

SERIES ESTABLISHED: San Bernardino County, California (Mojave River Area), 1978.

REMARKS: Classification of the Couthouse series is currently under investigation. It may be an Ustic intergrade.

Responsibility for this series was transferred from Davis to Phoenix 12/2015. The last revision to the series was 5/2001. ET

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National Cooperative Soil Survey
U.S.A.