LOCATION FROSTCIRCLE             AK

Established Series
Rev. MHC/DLM
05/2022

FROSTCIRCLE SERIES

Depth class: very shallow to deep to permafrost
Drainage class: poorly drained
Landforms: circles on mountains; stripes on mountains; circles on till plains; stripes on till plains
Parent material: silty eolian deposits over gravelly cryoturbate
Elevation: 2,365 to 5,295 feet (721 to 1,614 m)
Slope: 0 to 25 percent
Annual precipitation: 23 to 52 inches (583 to 1,310 mm)
Annual temperature: 25 degrees F (-4 degrees C)
Frost-free period: 50 to 80 days

TAXONOMIC CLASS:

TYPICAL PEDON: Frostcircle - on a slope of 12 percent under shrub birch/sedge scrub mosaic. (All colors are for moist soil). This profile is separated into two parts, the first part is in an intermound area troughs between circles; the second part is from within the convex circle center or boil. Mound-intermound topography consists of about 60 percent intermounds and 40 percent mounds. One complete cycle of mound-intermound occurs about every 4 meters.

Part I -- Convex circle centers

Oi--0 to 2 inches (0 to 5 cm); dark yellowish brown (10YR 3/4) and very dark brown (10YR 2/2) slightly decomposed plant material; many very fine and fine roots; very strongly acid (pH; clear wavy boundary.

AC--2 to 4 inches (5 to 10 cm); very dark grayish brown (2.5Y 3/2) silt loam; weak medium granular structure; very friable, nonsticky and nonplastic; common very fine and fine roots; strongly acid (pH 5.5); abrupt wavy boundary.

2Cgjj1--4 to 8 inches (10 to 20 cm); dark gray (5Y 4/1) gravelly loam; massive; friable, slightly sticky and slightly plastic; common very fine and fine roots; 15 percent gravel, 2 percent cobbles; strongly acid (pH 5.5); clear broken boundary.

2Cgjj2--8 to 15 inches (20 to 38 cm); dark gray (5Y 4/1) gravelly loam; massive; friable, slightly sticky and slightly plastic; few very fine and fine roots; 15 percent gravel, 2 percent cobbles; 5 mm strong brown (7.5YR 4/6) high chroma redox concentrations (approximately 25 percent of horizon); moderately acid; clear broken boundary.

2Cg--15 to 47 inches (38 to 120 cm); dark gray (5Y 4/1) gravelly loam; massive; friable, slightly sticky and slightly plastic; 15 percent gravel, 2 percent cobbles; moderately acid (pH 5.6); abrupt wavy boundary.

2Cgf--47 to 60 inches (120 to 152 cm); dark gray (5Y 4/1) permanently frozen gravelly loam; 15 percent gravel, 2 percent cobbles; moderately acid (pH 5.6).

Part II Troughs between circles

Oi--0 to 11 inches (0 to 28 cm); very dusky red (2.5YR 2.5/2) peat; many very fine, fine, and medium roots; very strongly acid (pH 5.0); gradual smooth boundary.

Oe--11 to 15 inches (28 to 38 cm); black (10YR 2/1) mucky peat; many very fine, fine, and medium roots; very strongly acid (pH 5.0); abrupt smooth boundary.

A/Cgjj--15 to 17 inches (38 to 43 cm); very dark brown (10YR 2/2) and dark gray (5Y 4/1) mucky silt loam; weak fine subangular blocky structure; very friable, nonsticky and nonplastic; common very fine and fine roots; strongly acid (pH 5.5); abrupt broken boundary.

2Cgf--17 to 60 inches (43 to 152 cm); dark gray (5Y 4/1) permanently frozen gravelly loam; 15 percent gravel, 2 percent cobbles; strongly acid (pH 5.4).

TYPE LOCATION: Delta River Area, Alaska; along the lower Delta River about 1 mile above the confluence of Phalen Creek; UTM coordinates: Zone 6, Easting 563207, Northing 7021068.

RANGE IN CHARACTERISTICS:

Soil moisture class: aquic
Average annual soil temperature: 32 to 30 degrees F (-0.1 to -1.0 degrees C)
Depth to permafrost: 8 to 60 inches (20 to 152 cm)

Oi and Oe horizons:
Colorhue of 2.5YR to 10YR; value of 2 to 3; chroma of 1 to 3
Texture-peat, mucky peat
Organic matter content65 to 90 percent
Rock fragments0 to 5 percent rounded very strongly cemented gravel
Reactionvery strongly acid to slightly acid

A and A part of A/Cgjj horizons:
Colorhue of 10YR or 2.5Y; value of 2 or 3; chroma of 1 to 3
Texturemucky silt loam; silt loam
Clay content0 to 10 percent
Silt content55 to 75 percent
Sand content15 to 35 percent
Organic matter content8 to 12 percent
Rock fragments0 to 5 percent rounded very strongly cemented gravel
Reactionstrongly acid to slightly acid

2ACF, 2Cg/Af, 2Cgf horizon:
Colorhue of 10YR to 5GY; value of 3 to 5; chroma of 1 t0 4
Texturecobbly sandy loam, gravelly loam or loam
Clay content5 to 25 percent
Silt content10 to 45 percent
Sand content40 to 75 percent
Rock fragments0 to 30 percent subangular strongly cemented gravel; 0 to 5 percent subangular strongly cemented cobbles
Reactionstrongly acid to slightly acid

COMPETING SERIES: This is the Distin series. Distin soils have a mean annual soil temperature less than 28 degrees F. (-2 degrees C).

GEOGRAPHIC SETTING:
Landforms: circles on mountains; stripes on mountains; circles on till plains; stripes on till plains
Parent material: silty eolian deposits over gravelly cryoturbate
Elevation: 2,365 to 5,295 feet (721 to 1,614 m)
Slope: 0 to 25 percent
Annual precipitation: 23 to 52 inches (583 to 1,310 mm)
Annual temperature: 25 degrees F (-4 degrees C)
Frost-free period: 50 to 80 days

GEOGRAPHICALLY ASSOCIATED SOILS: These include Fields, Minya, and Ogive soils. Fields soils are well drained, moderately deep, and occur on mountains. Minya soils are well drained, shallow, and occur on mountains. Ogive soils are somewhat poorly drained, very deep, and occur on mountains.

DRAINAGE AND PERMEABILITY: Poorly drained, very high runoff. Saturated hydraulic conductivity is moderately high to high above the permafrost and very low in the permafrost.

USE AND VEGETATION: Used for wildlife habitat and recreation. Native vegetation is shrub birch/sedge scrub mosaic.

DISTRIBUTION AND EXTENT: MLRA 228, Interior Alaska Mountains, Alaska. The series is of small extent.

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: WASILLA, ALASKA

SERIES ESTABLISHED: Delta River Area, Alaska, 2005

REMARKS: Diagnostic features and horizons recognized in this profile include:
Depth to permafrost: 11 to 60 inches. (2ACf, 2Cg/Ajjf, and 2Cgf horizons)
Organic soil material thickness: 0 to 15 inches. (Oi and Oe horizons)
Lithologic discontinuity: At the upper boundary of 2Cgjj horizon
Coarse-loamy particle size control section: 10 to 40 inches below the mineral soil surface
Temperature regime: pergelic
Moisture regime: aquic.

ADDITIONAL DATA:

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National Cooperative Soil Survey
U.S.A.