Rock-Ice Feature Inventory for the Sierra Nevada, California, USA

Summary

The Sierra Nevada is a tectonic uplift mountain range with a gradual gain in elevation on the west side and a steep escarpment on the east. Most of the mapped locations are east of the Sierran crest. The climate in the region is Mediterranean, with most of the precipitation in the winter months coming as snow at high elevations, but with some monsoonal precipitation in the summer, particularly in the southern end of the range. There is a very steep gradient in decreasing precipitation eastward from the Sierran crest as a result of rain-shadow orographic effects from the predominately eastward-moving Pacific frontal storms. PRISM-estimated (Daly et al. 1994) annual precipitation for the RIF locations ranged from 580 to 1880 mm; July precipitation from 5 to 33 mm. Mean annual maximum temperatures ranged from 1.8 to 15.2 oC, January from -5.7 to 6.2 oC, and July from 11 to 26.3 oC. Mean annual minima ranged from -8.1 to -0.4 oC, January from -15 to -7 oC, and July from 1.2 to 8.9 oC. The highest temperatures and lowest precipitation were largely at relict Pleistocene rock glaciers, which tended to be farthest east of the Sierran crest and lower in elevation. We mapped over 430 RIFs, based on field surveys and grouped them into six classes based on morphology and location. These categories constitute a greater range of frozen-ground features than are commonly described in rock-glacier surveys. Although granitic substrates dominate the Sierra Nevada, they do not in the eastern escarpment, so substrates in the RIF database are about equally divided between granitic and metamorphic. Ages of rock glaciers ranged from current (active) to relict (late Pleistocene). We interpreted the presence of outlet springs, basal lakes, suspended silt in outlet streams, and fringing phreatophytic vegetation, in addition to morphologic indications of current rock movement, as evidence for interstitial ice, either persistent or seasonal.

One comma-delimited ASCII file containing information for 430 rock-ice features is available.

Citing These Data

Millar, C. I. and R. D. Westfall. 2009. Rock-Ice Feature Inventory for the Sierra Nevada, California, USA. Boulder, CO: National Snow and Ice Data Center. Digital media.

Overview Table

Category	Description
Data format	comma-delimited ASCII text file (.csv)
Spatial coverage and resolution	Southernmost Latitude: 34.5°N Northernmost Latitude: 38.8°N Westernmost Longitude: 119.9°W Easternmost Longitude: 118.2°W
Temporal coverage and resolution	One time measurements from field surveys 2004 to 2008
File size	36 KB
Parameter(s)	rock-ice features including location, location class, elevation, age, aspect, shape, size, and presence of water
Procedures for obtaining data	Data are available via FTP.

Contacts

Investigators

Constance Millar
Robert Westfall
Sierra Nevada Research Center
Pacific Southwest Research Station
USDA Forest Service
800 Buchanan St.
Albany, CA 94710
Mailing address:
P.O. Box 245
Berkeley, CA 94701

Technical Contact

Detailed Data Description

Format

Comma-delimited ASCII text file (.csv) with the following columns:

1. Name of the watershed
2. Map id
3. Latitude (in decimal degrees north)
4. Longitude (in decimal degrees west)
5. Position types (these provide additional information about the positions within location classes (see Millar and Westfall (2008) for description of location classes): RGC (cirque rock glaciers) -Cq, cirque; -Va, extends down valley; -Mo, moraine; -Po, pocket glacier; RGV (valley wall rock glaciers) -Sc, scree; -Cl, cliff; Av, avalanche chute; -Ta, talus cone; BSC (boulder stream) -Sc, scree; -Cl, cliff; -Sn, snowfield apron; BST (streamside boulder stream) -St, streamside; PGA (alpine patterned ground) -La, lake margin; -NS, nets and stripes; Cr, sorted circles; MWA (alpine mass wasting) -So, solifluction fields)
6. Activity (M = modern; R = relict; ? uncertain)
7. Age (H = Holocene; P = Pleistocene, pre-Recess Peak (Late Glacial Maximum?); P-R = Pleistocene, Recess Peak; T, Tertiary?)
8. Mean elevation (meters above sea level; as average of upper and lower)
9. Upper elevation
10. Lower elevation
11. Aspect (in degrees from north; N=0)
12. Shape (1 = longer than wide; 0.5 = equal width and length; 0 = wider than long)
13. Size (1 = 0.5 ha; 2 = 5 ha; 3= 50 ha; 4 ≥ 400 ha)
14. Water (presence of water; 1 = ice, snow, or surface water present; 2 = running water audible but not visible; 3 = dry; a = unknown)

Spatial Coverage

The area investigated covers the Sierra Nevada range from 34.5o to 38.8o N latitude and -118.2o to -119.9o W longitude. The lowest elevation in the study area is 2225 m asl and the highest, 3932 m asl. The figure below shows the locations of the features.

Data Acquisition and Processing

Details of the collection methods and analysis can be found in Millar and Westfall (2008)

References and Related Publications

Daly, C., Neilson, R.P., Phillips, D.L. 1994. A statistical-topographic model for mapping climatological precipitation over mountainous terrain. Journal of Applied Meteorology 33:140-158.

Millar, C.I. and R.D. Westfall. 2008. Rock glaciers and periglacial rock-ice features in the Sierra Nevada; Classification, distribution, and climate relationships. Quaternary International, 188: 90-104.

Document Information

Document Creation Date

6 February 2009

Document URL

http://nsidc.org/data/docs/fgdc/ggd652_rockice_inventory_sierra/index.html