Galena creek rock glacier revisited—new observations on an old controversy

Abstract

Galena Creek rock glacier (GCRG), northwest Wyoming, exhibits most of the classic characteristics of rock glaciers. Clean ice with silty bands was found beneath a c. 1 m thick debris mantle by Potter. He inferred that the ice is glacigenic, originating in the small snowfield in the cirque at the head of GCRG. This view was challenged by Barsch, who asserted that the ice in GCRG is of "permafrost" origin. Since then GCRG has become a lightning rod for opponents and proponents of the glacigenic ice model for rock glaciers. We review evidence for that model here.Movement marks emplaced on GCRG in the 1960s were resurveyed in 1995 for a 30+ year record of movement. Maximum surface velocity is 45 cm/yr on gentle slopes and 80 cm/yr in a steep reach where GCRG spills out of the cirque. The less active, downvalley third of GCRG is moving at a maximum 14 cm/yr, and lobes formed between the more and less active parts have complex movement and are advancing down-valley over adjacent lobes at a maximum of 6.5 cm/yr. New refraction seismic profiles on GCRG were used to determine the thickness of the debris mantle over ice. On the up-valley, active part of GCRG, the debris mantle is a relatively uniform c. 1 m thick. On the down-valley, less active part, the thickness of the debris mantle is much more variable, but it is generally thicker. We cannot tell, on the basis of seismic data alone, whether the frozen material beneath the debris mantle is ice or a debris-ice mixture, but the results are not inconsistent with the glacigenic model for the origin of the ice. Two long-profiles in the cirque may identify bedrock at about 20-25 m depth.

Besiberris glacigenic rock glacier (Central Pyrenees, Spain) : mapping surface horizontal and vertical movement (1993-2003)

“…As Potter et al (1998) suggested, rock glaciers of glacigenic origin placed in an adverse climatic situation are starved systems in which the small accumulation of snow and ice is kept in balance only by the debris mantle that reduces ablation beneath it. Whalley et al (1995) have also indicated that with this configuration, the progressive thinning of the ice-core will give a reduction in velocity and, eventually, halt flow.…”

Radar Albedo Feature

“…Buried under an insulating debris layer (Harrison et al 2008;Potter 1972;Potter et al 1998;Whalley and Martin 1992), the ice is substantially protected from ablation. Unlike most dynamically active debris-covered glaciers, the ice core is thin Mtns, Wyoming (Potter 1972;Potter et al 1998) (Photo by WB Whalley).…”

“…Buried under an insulating debris layer (Harrison et al 2008;Potter 1972;Potter et al 1998;Whalley and Martin 1992), the ice is substantially protected from ablation. Unlike most dynamically active debris-covered glaciers, the ice core is thin Mtns, Wyoming (Potter 1972;Potter et al 1998) (Photo by WB Whalley). (Right) Glacier ice exposed on the side of a drained thermokarst lake, Gruben rock glacier, Wallis, Switzerland (Whalley 1979;Haeberli 1979;K€ a€ ab et al 1996) (Photo by WB Whalley) here, resulting in low creep rates.…”

The cryosphere and glacial permafrost as its integral component

“…The most influential are the first scientific papers [53,54], which are still the basis for the development of new viewpoints, especially, the ones which are most characteristic for the development of this field of research [55][56][57][58][59][60][61][62][63][64]. The number of interesting polemics in which sharp differences of opinion emerge also indicate scientists' engagement, and are essential for understanding the development of this field of knowledge [65][66][67][68][69][70][71][72][73][74][75]. Many of the articles contain a classification scheme for rock glaciers [76][77][78][79][80].…”