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Paraglacial processes, climate change and sediment supply |
Cold Regions Research Centre, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5 (e-mail: khewitt{at}wlu.ca)
The possible role of paraglacial adjustments in catastrophic rock-slope failures is investigated. Most of some 250 rockslide–rock-avalanche events identified in the Upper Indus Basin descended from slopes affected by Quaternary glaciations. Examples from the lower Gilgit Basin in the Karakoram Himalaya illustrate relations of rock-wall failure to former glacier activity and post-glacial responses, including sackung features. In many cases there is strong morphological evidence for paraglacial adjustments. However, other conditions must be considered as partial or alternative controls. They include a complex bedrock geology and seismo-tectonic conditions, and vertical shifts in periglacial and moisture climates. Given the enormous relief, the landslides themselves may involve a range of temporal and spatial distributions influenced by different topo-climates, geological terranes and stages of deglaciation. Meanwhile, post-glacial rock avalanche barriers have blocked and fragmented the river system. They exercise a major control over intermontane sedimentation and valley morphology. These impacts are treated as part of a broader ‘disturbance-regime’ geomorphology, where late Quaternary landscape evolution is driven by transient, but recurring, interactions among geomorphic process systems. Post-glacial conditions have also tended to partition the landscape into subunits with different mixes of geomorphic activity or rates of adjustment. The findings presented here depart from existing interpretations of Quaternary events in the region, and pose challenges for process geomorphology and the role of large landslides.
