Effects of a Debris Slide on “Sioux Glacier”, South-Central Alaska

Abstract

The lower one-third of “Sioux Glacier” in south-central Alaska was buried beneath a debris slide during the 27 March 1964 earthquake. Investigations to determine the effect of this cover on the regimen of the glacier revealed that it has increased in thickness by as much as 28 m, primarily as a result of the insulating effect of this debris cover. In areas where debris has continuously veneered the surface, at least since 1938, the ice is also thicker. A longitudinal profile reveals that the area near the upper extent of the slide debris has become intensely crevassed and has been lowered as much as 8 m between 1965 and 1966, while the terminal area is up to 5 m higher and is characterized by thrusting. It is concluded that a kinematic wave passed through this glacier sometime between 1965 and 1966.The upper zone of debris-veneered ice is moving at 175 m/year while the terminal area is flowing at only 21 m/year. The rate of down-glacier decrease in velocity is about 0.06 m/year per meter of horizontal distance except for an area approximately 1 km from the terminus. Here, the rate of decrease in velocity is 0.1 m/year per meter. The change in rate is presumed to be related to topographic control caused by the recent thinning of the ice here.

Moraine In-Transit as Parent Material for Soil Development and the Growth of Valdivian Rain Forest on Moving Ice: Casa Pangue Glacier, Mount Tronador (Lat. 41°10's), Chile

“…The arcs are higher than the neighbouring depressions, but this may be considered an effect of insulation by the thicker till cover, which protects the underlying ice. This would explain the persistence of the ice-crests under the arcs, and agrees with the observations of Reid (1969[a] and [b], 1970[a] and [b]), Reid and Callender (1965), Post (1967), and Marangunic and Bull (1968), among others. Supraglacial till originated mainly as landslide debris and partially as rock avalanches on the glacier surface.…”

Rapid advance of two mountain glaciers in response to mine‐related debris loading

“…However, it is nonetheless an appropriate upper end‐member analogue for potential landslide‐induced advances of alpine glacier systems where the ratio of supraglacial rock mass originating from a landslide versus glacier ice mass tends to be higher. The Kumtor example can therefore augment the small number of cases, where estimates have been secured for both prelandslide and postlandslide glacier velocities [e.g., Shugar et al , ], and constitutes a clear analogue for mass‐induced increases in driving stress with similar glaciological responses to those reported by Reid [] for the landslide‐induced kinematic wave in Sioux Glacier, Alaska.…”

“…In the natural environment, the addition of debris to a glacier surface most often occurs as a result of landslides. The impact of rapid increases in supraglacial debris load on mountain glaciers, specifically the catastrophic deposition of landslide debris, has been reported from several settings in which the immediate glacier response was to advance or surge [e.g., Tarr , ; Bull and Marangunic , , ; Reid , ; Gardner and Hewitt , ; Deline , ; Shugar et al , ]. Various mechanisms have been proposed to explain such events.…”

“…More immediate responses by glaciers to sudden additions of large supraglacial debris loads could be related to mass‐induced increases in driving stress. For example, Reid [] describes the passing of a kinematic wave through the Sioux Glacier in Alaska and concomitant snout thickening 1 year after a landslide fell onto the ice surface. However, a similar event on the Bualtar Glacier, Pakistan Himalaya, is explained by Gardner and Hewitt [] as an interruption of the glacial hydrological system and thereby indirectly related to the landslide.…”

A Surge of Bualtar Glacier, Karakoram Range, Pakistan: A Possible Landslide Trigger

“…Some research suggests relationships between the glaciation/ deglaciation process and slope failures (Whalley, 1974;Evans and Clague, 1988). Cases such as the Sherman Glacier rockslide of 1964 (Shreve, 1966), the Tahoma rockfall on Mount Rainier (Crandell and Fahnestock, 1965), the Sioux Glacier rock avalanche (Reid, 1969), the South Georgia rockslide (Gordon and others, 1978), and the Brenva Glacier rockfall in 1920 (Porter and Orombelli, 1981) have permitted some consideration of the impacts of large slope failures on glacier systems. The Bualtar Glacier case, described in this paper, provides a further opportunity to examine some of these relationships.…”