Rock Streams in the Sierra Nevada, California

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. American Geographical Society is collaborating with JSTOR to digitize, preserve and extend access to Geographical Review. HE terms "rock stream" and "rock glacier" have been applied to voluminous tongue-shaped accumulations of rubble and blocks encountered in the mountains of Colorado,1 Wyoming,2 and Alaska3 and in the Alps.' Their scattered occurrence in regions so widely separated suggests a much greater frequency than the published accounts indicate. The presence of rock streams in the Sierra Nevada substantiates this conclusion.The wrinkled surface of the rock streams has challenged the imagination of geomorphologists, who have compared them to lava flows, mudflows, and glaciers. Similarly varied are the interpretations of their origin. They have been explained as glacial moraines,5 as deposits of landslides of the rockfall type,6 as landslide material transported a short distance by small glaciers,7 as the result of creep of landslide deposits,8 as creeping talus,9 and as a special form of denudation associated with dying glaciers;10 and smaller rock streams have also been interpreted as accumulations of talus at the foot of temporary snowbanks.'1 The variety of single interpretations has invited compromise in the form of compound explanations. Sliding of talus over snowbanks, creeping, slumping, and sliding of the regolithic mass, and incipient glacial motion have been combined in one explanation ;12 in another retreat of glaciers has been added to this group of processes ;13 1 Whitman Cross and Ernest Howe: Geography and General Geology of the [Silverton] Quadrangle, [Colorado], U. S. Geol. Survey Geol.

Quaternary stratigraphy of the La Sal Mountains, Utah

“…The headward zone is of course lacking where it has been reworked by younger rock glaciers, but none of the rock glaciers terminate abruptly headward in ice-contact slopes. This suggests that they did not form downvalley from a glacier, as has been observed by Capps (1910) and others in Alaska and inferred by Kesseli (1941) for some in the Sierra Nevada. Some rock glaciers have merely irregular hummocky surfaces.…”

Stone Stripes and Other Surface Features of Tinto Hill

“…The fact that no gullying is to be found on striped ground, however steep, suggests that they assist in the disposal of surface water and that this must be taken into account in explaining them. Only on the steepest slopes at the bottom of Maurice's Cleugh does wash give rise to runnels and very shallow gullies, but in that deep and sunless hollow conditions are quite exceptional and have given rise to a tongue of debris about 6 feet long and 2 feet high, closely resembling, on a miniature scale, the rock glaciers figured by Kessel (1941). The stripes have been visited after a period of frequent freezing and thawing weather, without rain, and many examples observed of material actually heaved into a position which wind and rain would quickly level again.…”

On the Development of Transverse Ridges on Rock Glaciers

“…Active rock glaciers have been identified in a variety of alpine environments, including the Sierra Nevada (Kesseli , 1941), the Andes (Lliboutry, 1953;Corte, 1976), the Himalaya (Mayewski and others, 1981), the Swiss Alps (Chaix, 1923), the Alaska Range (Wahrhaftig and Cox, 1959), the Brooks Range, Alaska (Calkin and others, 1987), and throughout the American and Canadian Rockies (e.g. Brown, 1925;Richmond, 1952;Potter, 1972;Luckman and Crockett, 1978;Harris, 1981).…”

“…This latter characteristic has led many researchers to speculate that all rock glaciers are merely debris-covered ice glaciers and that their movement is derived solely from the creep of the ice core (e.g. Brown , 1925;Kesseli, 1941;Whalley, 1974;Corte, 1976). Other researchers have suggested that "tongue-shaped" rock glaciers Joul'I1al 0/ Glaciology represent debris-covered relict ice glaciers and/or ice-cored moraines, while the lobate forms are constructed entirely of rock debris cemented with interstitial ice (Outcalt and Benedict, 1965;Madole, 1972).…”