LOCATION MOAPA NV
Established Series
Rev. LNL/VDL/ELS/LJL/ET
11/2015
MOAPA SERIES
The Moapa series consists of moderately deep, excessively drained soils that formed in eolian sands over sandstone. Moapa soils are on sand sheet over rock pediments. Slope ranges from 4 to 30 percent. The mean annual precipitation is about 6 inches and the mean annual air temperature is about 66 degrees F.
TAXONOMIC CLASS: Mixed, thermic Typic Torripsamments
TYPICAL PEDON: Moapa fine sand, rangeland and wildlife habitat. (Colors are for dry soil unless otherwise noted.)
A--0 to 4 inches; light yellowish brown (10YR 6/4) fine sand, dark yellowish brown (10YR 4/4) moist; single grained; loose; nonsticky and nonplastic; many very fine roots; many very fine interstitial pores; slightly effervescent; moderately alkaline (pH 8.2); clear smooth boundary. (2 to 6 inches thick)
C1--4 to 12 inches; light yellowish brown (10YR 6/4) fine sand, dark yellowish brown (10YR 4/4) moist; single grain; loose, nonsticky and nonplastic; common fine and very fine roots; many very fine interstitial pores; strongly effervescent; strongly alkaline (pH 8.6); clear smooth boundary.
C2--12 to 30 inches; light yellowish brown (10YR 6/4) fine sand, yellowish brown (10YR 5/4) moist; single grain; loose, nonsticky and nonplastic; fine and common very fine roots; many very fine interstitial pores; strongly effervescent; strongly alkaline (pH 8.6); abrupt wavy boundary. (Combined thickness of C horizons is 15 to 36 inches.)
2Cr--30 to 36 inches; very pale brown (10YR 8/2) weathered sandstone, very pale brown (10YR 7/3) moist; very hard, very firm; can be dug with a tile spade with difficulty; strongly effervescent. (1 to 6 inches thick)
2R--36 inches; calcareous sandstone.
TYPE LOCATION: Clark County, Nevada; approximately 8 miles southwest of the junction of Interstate 15 and Nevada Highway 12 in the Valley of Fire State Park; about 600 feet east and 700 feet south of the northwest corner of section 7, T. 16 S., R. 67 E., Mount Diablo base line and meridian. 36 degrees, 33 minutes, 42 seconds north latitude and 114 degrees, 32 minutes, 38 seconds west longitude; UTM 11, 719802e, 4049055n; NAD 93.
RANGE IN CHARACTERISTICS:
Soil moisture - Usually dry, moist in some part during winter and spring and intermittingly moist in the upper part following summer convection storms; typic aridic moisture regime.
Soil temperature - 66 to 71 degrees F.
Depth to paralithic contact - 21 to 38 inches.
Depth to bedrock - 22 to 40 inches.
Control section - Percent clay: 0 to 5 percent.
Rock fragments: Averages 0 to 15 percent, mainly gravel less than 2 inches in diameter.
A horizon - Hue: 10YR through 2.5YR.
Value: 6 or 7 dry, 4 through 6 moist.
Chroma: 3 through 6 dry or moist.
Effervescence: Non effervescent to violently effervescent.
Calcium carbonate equivalent in the fine earth fraction: 1 to 10 percent.
C horizons - Hue: 10YR through 2.5YR.
Value: 6 or 7 dry, 4 through 6 moist.
Chroma: 3 through 6 dry or moist.
Texture: Fine sand or sand,.
Effervescence: Non effervescent to violently effervescent.
Reaction: Moderately alkaline to strongly alkaline.
Calcium carbonate equivalent in the fine earth fraction: 1 to 15 percent.
Other features: Few or common medium or coarse irregular soft masses of calcium carbonate at the paralithic contact. It is not diagnostic. Some pedons have thin calcium carbonate coats that are randomly oriented on rock fragments. Some pedons may have a horizon with 15 to 30 percent gravel.
COMPETING SERIES: These are the Atina (TX),
Azulugar (TX),
Bluepoint (NV),
Brazito (NM),
Cajon (CA),
Copia (NM),
Maynard Lake (NV),
Pintura (UT),
Toquop (NV),
University T(NM) and
Yturbide (NM) series. All of these soils are greater than 60 inches deep. Maynard Lake soils have more than 20 percent volcanic ash or pumice.
GEOGRAPHIC SETTING: Moapa soils are on sand sheets over rock pediments. These soils formed in eolian sands over sandstone. Slope ranges from 4 to 30 percent. Elevations are 1,650 to 2,300 feet. The climate is hot and arid with warm, moist winters and hot, dry summers. The mean annual precipitation is 5 to 7 inches; mean annual air temperature is 64 to 70 degrees F., and the frost-free season is 240 to 320 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the
St. Thomas,
Bard, and
Arrolime soils. St. Thomas soils contain over 50 percent coarse fragments in the control section. Bard soils have lime-indurated hardpans. Arrolime soils have loamy-skeletal control sections and gypsic mineralogy.
DRAINAGE AND PERMEABILITY: Excessively drained; high runoff; rapid permeability.
USE AND VEGETATION: These soils are used for rangeland and wildlife habitat. The present vegetation is mainly big galleta, Indian ricegrass, white bursage, Nevada ephedra and winterfat.
DISTRIBUTION AND EXTENT: Mojave Desert of southern Nevada;MLRA 30. These soils are not extensive.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: PHOENIX, ARIZONA
SERIES ESTABLISHED: Clark County (Virgin River Area), Nevada, 1970. The name is coined from the town of Moapa, Nevada.
REMARKS: Moapa soils were classified as Regosols. Diagnostic horizons and features recognized in this pedon are:
Ochric epipedon - 0 to 7 inches (A and part of the C1 horizons).
Paralithic contact - 30 inches (2Cr layer).
Particle-size control section - 10 to 30 inches (C2 and part of the C1 horizons).
Responsibility for this series was transferred from Davis to Phoenix 11/2015. The last revision to the series was 4/2006. ET
National Cooperative Soil Survey
U.S.A.