Transglacial Hazards: Karakoram and NW Himalaya, inner Asia

Abstract

In high mountain environments glacial and landslide hazards can be causally interdependent. They help prepare, trigger, transform or constrain each other, and related geohazards. Interactions between massive rock slope failures (MRSFs) and glaciers are examined, with examples from theGreater KarakoramHimalaya region. TheMRSFs of interest generate rock avalanches. Rock avalanches and glacial processes affect each other in several ways, may include off-ice as well as on-ice landslide effects and are identified as transglacial hazards. Verticality is a key concern as gravity driven processes in high relief areas pass through different clima-geomorphic regimes with effects on the nature and severity of the landslides and secondary hazards associated with them. Since 1985 fourteen such MRSFs have been reported in the region. The recent record, if at all representative, suggests as many as 50 MRSFs per century in these glacier basins, and 5,000 in the Holocene. Climate change may affect recent events through rock wall debuttressing where glaciers retreat, or from degrading permafrost. However, MRSFs are especially identified with earthquakes. Geomorphic evidence suggests concentrated landslide episodes from large earthquakes, and the regionmay be subject to rare mega-quakes. Of the many more prehistoric rock avalanches identified from deposits in ice-free areas, more than 30 descended out of glacier basins. Short case histories illustrate the different styles of event and hazard potential. They include some mass flow events with longest run outs and greatest catastrophic potential. Risk profiles are complicated and compounded by landslide and glacier impoundments, glacier advances including surges, and outburst floods. Landslide-driven thickening, advances and deposits out-of-phase with climate complicate the glacial record. Rapidly growing mountain populations and towns, resource activity and infrastructure projects, increase exposure to the risks involved.