Nature and timing of large landslides in the Himalaya and Transhimalaya of northern India |
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| Authors: | Jason M Dortch Lewis A Owen William C Haneberg Marc W Caffee Craig Dietsch Ulrich Kamp |
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| Institution: | 1. Department of Geology, University of Cincinnati, Cincinnati, OH 45221, USA;2. Haneberg Geoscience, 10208 39th Avenue SW, Seattle WA 98146, USA;3. Department of Physics/PRIME Laboratory, Purdue University, West Lafayette, IN 47906, USA;4. Department of Geography, The University of Montana, Missoula, MT 59812, USA;1. Université catholique de Louvain, Earth and Life Institute, Georges Lemaître Centre for Earth and Climate Research, Place Louis Pasteur 3 boîte L4.03.08, 1348 Louvain-la-Neuve, Belgium;2. Fund for Scientific Research – FNRS, Rue d’Egmont 5, 1000 Brussels, Belgium;1. Department of Geology, University of Cincinnati, Cincinnati, OH 45221, USA;2. School of Environment and Development, The University of Manchester, M0 1QD, UK;3. Department of Physics/PRIME Laboratory, Purdue University, West Lafayette, IN 47906, USA;4. Department of Geography, Senckenbergstr. 1, Justus-Liebig-University Giessen, D-35390 Giessen, Germany;5. Fugro GeoConsulting, Inc., 6100 Hillcroft, Houston, TX 77081, USA;6. Centre for the Study of Regional Development, Jawaharlal Nehru University, New Delhi 110067, India;1. Key Laboratory of Mountain Hazards and Earth Surface Processes, Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China;2. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China;3. China-Pakistan joint Research Center on Earth Sciences, Islamabad, Pakistan;4. University of Chinese Academy of Sciences, Beijing 100049, China |
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| Abstract: | Four large landslides, each with a debris volume >106 m3, in the Himalaya and Transhimalaya of northern India were examined, mapped, and dated using 10Be terrestrial cosmogenic radionuclide surface exposure dating. The landslides date to 7.7±1.0 ka (Darcha), 7.9±0.8 ka (Patseo), 6.6±0.4 ka (Kelang Serai), and 8.5±0.5 ka (Chilam). Comparison of slip surface dips and physically reasonable angles of internal friction suggests that the landslides may have been triggered by increased pore water pressure, seismic shaking, or a combination of these two processes. However, the steepness of discontinuities in the Darcha rock-slope, suggests that it was more likely to have started as a consequence of gravitationally-induced buckling of planar slabs. Deglaciation of the region occurred more than 2000 years before the Darcha, Patseo, and Kelang Serai landslides; it is unlikely that glacial debuttressing was responsible for triggering the landslides. The four landslides, their causes, potential triggers and mechanisms, and their ages are compared to 12 previously dated large landslides in the region. Fourteen of the 16 dated landslides occurred during periods of intensified monsoons. Seismic shaking, however, cannot be ruled out as a mechanism for landslide initiation, because the Himalaya has experienced great earthquakes on centennial to millennial timescales. The average Holocene landscape lowering due to large landslides for the Lahul region, which contains the Darcha, Patseo, and Kelang Serai landslides, is ～0.12 mm/yr. Previously published large-landslide landscape-lowering rates for the Himalaya differ significantly. Furthermore, regional glacial and fluvial denudation rates for the Himalaya are more than an order of magnitude greater. This difference highlights the lack of large-landslide data, lack of chronology, problems associated with single catchment/large landslide-based calculations, and the need for regional landscape-lowering determinations over a standardized time period. |
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