LOCATION ROUNDKNOLL IDEstablished Series
TAXONOMIC CLASS: Ashy-skeletal, glassy, frigid Typic Vitrixerands
TYPICAL PEDON: Roundknoll gravelly ashy loamy sand - on a 10 percent slope at an elevation of 5,600 feet in rangeland. When described on June 3, 1997, the soil was dry. (Colors are for dry soil unless otherwise noted.)
A1--0 to 3 inches; brown (10YR 5/3) gravelly ashy loamy sand, dark brown (10YR 3/3) moist; weak fine granular structure; soft, very friable, nonsticky and nonplastic; common very fine and fine roots; many very fine interstitial pores; about 15 percent cinders; slightly alkaline (pH 7.5); clear smooth boundary. (1 to 4 inches thick)
A2--3 to 10 inches; yellowish brown (10YR 5/4) gravelly ashy loamy sand, dark yellowish brown (10YR 3/4) moist; weak very fine subangular blocky structure; soft, very friable, nonsticky and nonplastic; common very fine, fine roots; many very fine and fine interstitial pores; about 30 percent cinders; slightly alkaline (pH 7.7); clear smooth boundary. (4 to 10 inches thick)
Bw--10 to 15 inches; brown (10YR 5/3) extremely gravelly ashy loamy sand, brown (10YR 4/3) moist; single grained; loose; common very fine and fine roots; many very fine and fine and few medium interstitial pores; about 60 percent cinders; slightly alkaline (pH 7.6); clear smooth boundary. (3 to 8 inches thick)
Bk1--15 to 20 inches; brown (10YR 5/3) very gravelly ashy loamy sand, brown (10YR 4/3) moist; single grained; loose; few very fine roots; many very fine , fine and medium interstitial pores; about 50 percent cinders; carbonates are on the cinders and are violently effervescent; slightly alkaline (pH 7.7); clear smooth boundary. (4 to 8 inches thick)
Bk2--20 to 30 inches; pale brown (10YR 6/3) extremely gravelly ashy loamy sand, brown (10YR 4/3) moist; single grained; loose; few very fine roots; many very fine, fine and medium interstitial pores; about 60 percent cinders; carbonates are on cinders and are violently effervescent; moderately alkaline (pH 7.9); clear smooth boundary. (8 to 12 inches thick)
Bk3--30 to 60 inches; pale brown (10YR 6/3) extremely gravelly ashy sand, brown (10YR 4/3) moist; single grained; loose; many very fine, fine and medium interstitial pores; about 80 percent cinders; carbonates are on cinders and are violently effervescent; moderately alkaline (pH 7.9).
TYPE LOCATION: Butte County, Idaho about 1.5 miles east of Craters of the Moon visitor center; 900 feet east and 1,900 feet south of the northwest corner of sec. 27, T. 2 N., R. 25 E. Latitude 43 degrees, 28 minutes, 35 seconds north; Longitude 113 degrees, 28 minutes, 20 seconds west.
RANGE IN CHARACTERISTICS:
The soil moisture control section is dry for 100 to 120 consective days.
Mean annual soil temperature - 42 to 47 degrees F.
Reaction - slightly alkaline to moderately alkaline throughout increasing with depth
Andic soil properties -
Glass content is 30 to 50 percent
Phosphate retention is 25 to 50 percent
Acid oxalate aluminum plus one-half the acid oxalate iron is 0.4 to 1.0
15-bar water, dry is 12 to 15 and moist is 10 to 20 percent.
Depth to carbonates (calcic horizon) is 10 to 20 inches
Particle-size control section averages 50 to 70 percent cinders
A horizon
Value - 4 or 5 dry
Chroma - 3 or 4 moist or dry
Rock fragments - 15 to 35 percent cinders
Bw horizon
Value - 4 or 5 dry, 3 or 4 moist
Chroma - 3 or 4 moist or dry
Texture - GRV-LS, GRX-LS
Rock fragments - 45 to 60 percent
Bk horizon
Value - 5 or 6 dry, 3 or 4 moist
Chroma - 2 through 4 moist or dry
Textures - GRV-LS, GRX-LS, GRX-S
Rock fragments - 50 to 90 percent cinders
Calcium carbonate - 5 to 15 percent
COMPETING SERIES: There are no competing series.
GEOGRAPHIC SETTING: Roundknoll soils are on kipukas on recent basalt plains and associated with lava flows. Slopes range from 2 to 20 percent. Elevation ranges from 5,400 to 5,800 feet. The soil formed in wind deposited volcanic tephra. The mean annual precipitation is 14 to 18 inches, most of which falls as snow and early spring rain. The mean annual air temperature is about 40 to 45 degrees F. The frost-free season is 60 to 90 days.
GEOGRAPHICALLY ASSOCIATED SOILS: These are lava flows.
DRAINAGE AND PERMEABILITY: Well drained. Rapid runoff. Rapid over very rapid permeability.
USE AND VEGETATION: Mainly used for wildlife. Vegetation is mountain big sagebrush, lava fernbush, snowberry, bitterbrush, and bluebunch wheatgrass.
DISTRIBUTION AND EXTENT: South-central Idaho. This series is of limited extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Portland, Oregon
SERIES ESTABLISHED: Craters of the Moon Area, Idaho, 1999.
REMARKS: Diagnostic horizons and features recognized in this pedon are:
Andic soil properties -
Glass content - 40 percent
Phosphate retention - 30 percent
Acid oxalate aluminum plus one-half the iron - 0.6
15 bar water dry 8 and moist 12
Particle-size control section - 0 to 40 inches averages 55 percent cinders
Ochric epipedon - mollic colors only extend to 3 inches
Calcic horizon - 15 to 60 inches; over 5 percent calcium carbonate.