LOCATION VULCAN                  CO

Established Series
Rev. RHM/KLS
09/2022

VULCAN SERIES

The Vulcan series consists of very deep, well drained soils that formed in very stony materials weathered from highly fractured rhyolite or similar bedrock on gently to steeply sloping mesa tops and sides. Slope ranges from 2 to 30 percent or more. Mean annual precipitation is about 510 mm and mean annual air temperature is about 1 degrees C.

TAXONOMIC CLASS: Clayey-skeletal, smectitic Ustic Glossocryalfs

TYPICAL PEDON: Vulcan very gravelly sandy loam - forest. (Colors are for dry soil unless otherwise stated.)

Oi--0 to 8 cm; undecomposed organic material, chiefly needles, bark, twigs, and leaves.

Oe--8 to 11 cm; partially decomposed organic material like that of the horizon above. (Combined thickness of O horizons - 1 to 10 cm)

E--11 to 31 cm; light gray (10YR 7/2) very gravelly sandy loam, light brownish gray (10YR 6/2) moist weak thin platy structure that parts to fine granules; soft, very friable; 60 percent gravel; slightly acid; gradual irregular boundary. (15 to 25 cm thick)

E/Bt--31 to 51 cm; mixed light gray (10YR 7/2) and yellowish brown (10YR 5/4) very stony sandy clay loam (composite texture), light brownish gray (10YR 6/2) and reddish brown (5YR 4/4) moist; moderate fine subangular blocky structure; slightly hard, very friable, slightly sticky slightly plastic; peds are very hard, firm; this horizon contains seams and nodules of clayey material like that of the underlying horizon imbedded in a matrix like that of the overlying horizon; few thin patchy clay films on some of the more clayey peds; 60 percent stones; moderately acid; gradual wavy boundary. (8 to 25 cm thick)

Bt--51 to 102 cm; reddish brown (5YR 5/4) very stony clay, reddish brown (5YR 4/4) moist; moderate medium and fine subangular and angular blocky structure; slightly hard, friable, sticky plastic; peds are extremely hard, very firm; thin continuous clay films on peds and in root channels and pores; 60 percent stones; moderately acid; gradual wavy boundary. (20 to 50 cm thick)

2C--102 to 163 cm; fragmental deposits of fractured rhyolite bedrock, consisting mainly of overlapping rhyolite flagstone that may or may not be oriented to the horizontal axis, and with voids 3 to 10 cm across that are not filled with fine materials.

TYPE LOCATION: Saguache County, Colorado; near the southwest corner of Sec. 29, T. 47 N., R. 2 E.

RANGE IN CHARACTERISTICS:
Mean annual soil temperature--3 degrees C
Mean summer soil temperature--8 degrees C
Depth to the top of the argillic horizon--less than 60 cm
Depth to the base of the argillic horizon--40 to 100 cm
Base saturation--60 to 100 percent in all subhorizons of the argillic horizon
Depth to fragmental 2C horizons--50 to 100 cm
Rock fragment content--35 to 75 percent in a major part of the solum and any C horizon and are mainly 250 to 1000 mm in diameter
Reaction--pH 5.6 to 7.8

Thin A horizons or C horizons occur in some pedons.
These soils are noncalcareous throughout.

E horizon
Hue--10YR through 5YR
Value--5 through 8 dry, 4 through 7 moist
Chroma--1 through 4

Bt horizon
Hue--5YR through 10R
Value--5 through 7 dry, 4 through 6 moist
Chroma--1 through 6
Texture--very stony or extremely stony clay loam, clay, or sandy clay
Clay content--35 to 50 percent of the fine earth fraction
Silt content--5 to 40 percent
Sand content--15 to 55 percent with more than 15 percent being fine or coarser sand

COMPETING SERIES: These are the Chris, Nutras and Seitz series. These soils lack fragmental 2C horizons at depths of less than 125 cm. Also, Chris soils have coarse fragments mainly less than 25 cm in diameter and Seitz soils have hue of 7.5YR or yellower in the Bt horizon.

GEOGRAPHIC SETTING:
Landform--mesa tops and sides
Slope--2 to 30 or more percent
Parent Material--very stony materials weathered from highly fractured rhyolite or similar bedrock
Mean annual precipitation--510 mm with peak periods of precipitation occurring during the spring and summer
Mean annual air temperature--1 degree C
Mean summer temperature--8 degrees C

GEOGRAPHICALLY ASSOCIATED SOILS: None listed

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

USE AND VEGETATION: These soils are used for forestry, native pastureland, or for recreational purposes. Native vegetation is mainly Douglas-fir, Engelmann spruce, aspen and common juniper with a weak understory of grasses and shrubs.

DISTRIBUTION AND EXTENT: The Vulcan series is moderately extensive in the mountains of central Colorado; MLRA 48A

SOIL SURVEY REGIONAL OFFICE (SSRO) RESPONSIBLE: Bozeman, Montana

SERIES ESTABLISHED: Saguache County, Colorado, 1974

REMARKS: Converted to metric, updated formatting, and O horizons were updated to start at zero. Competing series section was not updated. 9/2022

Vulcan soils have a cryic temperature regime and a udic soil moisture regime with an ustic subclass.

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National Cooperative Soil Survey
U.S.A.