Morphology and surface structures of Maxwell Creek rock glaciers, St Elias mountains, Yukon: rheological implications

Abstract

The dominant role of mass movement processes in the formation of south‐west Yukon paraglacial landscapes is exemplified by a tributary of Maxwell Creek. Rock glaciers occur along most of the length of the mid‐valley. Two large rock glaciers flowing from cirques on the east and west sides of the valley are confluent in the centre of the valley, and have a combined lobe extending 1 km downvalley. Morphological contrasts between the moraines and flow lobes of the east form, and the flow ridges of the west form, indicate different processes of movement at the surface. Sections in the surface deposits indicate movement of the mass of material in the lobes but demonstrate a combination of overriding and compression flow in the ridges. Near surface composition varies from large boulders with voids, to boulders with gravel and fines matrix and with the ice content varying from interstitial to massive infilling of the voids. Palaeosols sampled 1 m underneath overriding ridges were dated at 1480 and 660 a BP. The rock glaciers produced a combined central valley landform at the end of the Wisconsin. Neoglacial activity resulted only in confluence of the rock glaciers, without extension downvalley. The combination of the compressional and overriding ridges with the variability of the sediments and ice content is indicative of a complex surface rheology. Comparison with the ridges and lobes of rock glaciers in other valleys suggests that this surface variability is common on the rock glaciers of the southwest Yukon. © 1998 John Wiley & Sons, Ltd.

Development of transverse ridges on rock glaciers: field measurements and laboratory experiments

“…Moreover, both processes or parts of them seem to be in operation (cf. Wahrhaftig and Cox, 1959;White, 1987;Johnson, 1998). Overthrusting certainly plays a role for the large-magnitude surface undulations on Muragl (Figure 4) and Suvretta rock glaciers.…”

Towards a palaeoclimatic model of rock-glacier formation in the Swiss Alps

“…Many independent dating methods point to a general rock-glacier age in the range of millennia (e.g. relative age dating: Birkeland, 1973; surface weathering: Kirkbride and Brazier, 1995; Humlum, 1998; fossil soils: Johnson, 1998; geochemical data: Steig and others, 1998; radiocarbon age: Haeberli and others, 1999). At the same time, such studies give concise evidence that rock glaciers can display a complex, multi-system temporal behaviour.…”