LOCATION HOPKINS COEstablished Series
TAXONOMIC CLASS: Fine-loamy over fragmental, mixed, superactive Ustic Haplocryolls
TYPICAL PEDON: Hopkins channery loam - grassland. (Colors are for dry soil unless otherwise noted.)
A--0 to 12 inches; grayish brown (10YR 5/2) channery loam, very dark grayish brown (10YR 3/2) moist; strong fine granular structure; soft, very friable; 20 percent flat rhyolite fragments; mildly alkaline; gradual wavy boundary. (6 to 15 inches thick)
C1--12 to 16 inches; light brownish gray (10YR 6/2) channery loam, grayish brown (10YR 4/2) moist; massive; slightly hard, very friable; 20 percent flat rhyolite fragments; calcareous; moderately alkaline; irregular wavy boundary. (0 to 10 inches thick)
C2--16 to 60 inches; overlapping flagstones of rhyolite separated by unfilled voids 1/2 to 4 inches in diameter.
TYPE LOCATION: Gunnison County, Colorado, SE1/4 of Sec. 27, T. 49 N., R. 2 E. at elevations of 8,900 to 9,000 feet.
RANGE IN CHARACTERISTICS: Thickness of the mollic epipedon ranges from 7 to 15 inches, depth to calcareous material ranges from 6 to 15 inches, and depth to C2 horizon material ranges from 14 to 20 inches. The organic carbon content of the mollic epipedon ranges from .8 to 1.5 percent and decreases uniformly with increasing depth. Calcium carbonate equivalent ranges from less than 1 to 3 percent but there is no continuous distinct horizon of secondary carbonate accumulation, although coatings of calcium carbonate may occur on some of the rock fragments in the upper portions of C2 horizon. The upper portion of the control section ranges in clay from 18 to 35 percent. Rock fragments are up to 6 inches in length and range from 15 to 35 percent. Rock fragments in the C2 horizon range from 35 to 90 percent by volume and from 6 to 15 inches in length. The mean annual soil temperature ranges from 40 to 46 degrees F, and the summer soil temperature ranges from 52 to 59 degrees F.
The A horizon has hue of 2.5Y through 7.5YR, value of 4 or 5, 2 or 3 moist, and chroma of 2 or 3. It ranges from slightly hard to soft and is neutral to mildly alkaline.
The C horizon has hue of 2.5Y through 7.5YR. It is neutral through moderately alkaline.
COMPETING SERIES: There are currently no other series in this family. Closely related soils are Ruby, Searing, and Sizer series. Ruby and Sizer soils in another subgroup have an argillic horizon. Searing soils have mean summer soil temperatures greater than 59 degrees F.
GEOGRAPHIC SETTING: Hopkins soils are on upland hills, ridges, and valley side slopes. Slope gradients range from 2 to more than 30 percent. The soils formed from highly fractured rhyolite or deposits of very coarse textured rhyolitic colluvium. The average annual precipitation is 18 inches with peak periods of precipitation occurring during the spring and summer. Mean annual temperature is 36 to 44 degrees F.
GEOGRAPHICALLY ASSOCIATED SOILS: These are the Parlin and Vulcan soils. Parlin soils have an argillic horizon. Vulcan soils have a clayey-skeletal particle size control section.
DRAINAGE AND PERMEABILITY: Well to somewhat excessively drained; slow to medium runoff; medium to rapid permeability.
USE AND VEGETATION: These soils are used principally as native pastureland. Native vegetation is mainly mutton grass, big sagebrush, western wheatgrass, pine needlegrass, needleandthread, and squirreltail.
DISTRIBUTION AND EXTENT: Mountainous areas of west-central Colorado. The series is of moderate extent.
MLRA SOIL SURVEY REGIONAL OFFICE (MO) RESPONSIBLE: Bozeman, Montana
SERIES ESTABLISHED: Gunnison County, Colorado, 1975.