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| Titel |
Giant landslides from the inside |
| VerfasserIn |
J. T. Weidinger, S. Dunning, O. Korup |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250025973
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| Zusammenfassung |
| Despite the growing literature on catastrophic long-runout landslides, few studies have
systematically examined sedimentary and petrographic characteristics of the interior of
large landslide deposits, which yield valuable insights into dynamics during motion
and final emplacement. We summarize petrographic evidence of dynamic rock
fragmentation, internal sliding surfaces, and basal frictional melt that together allow
constraining the dynamics and emplacement mechanisms of nine giant (> 1 km3)
landslides in the Alps, the Himalayas, and the Tien Shan. We find that the fractal
particle size distribution in some of these rock-avalanche deposits is similar to that
found for fault-zone rocks, deforming glacial tills, and volcanic debris avalanches,
suggesting a strong link through a formational mechanism consistent with confined
comminution models. We propose a model in which giant landslide sedimentology evolves
during runout, from initially intact, discontinuity-defined rock slides with shear
focused at the base, to the final stratified fragmented sand and gravel deposits. Mature
deposits show shear distributed throughout the mass with near equal probability of
fragmentation across all clast sizes with additional zones of concentrated shear
related to weak lithologies. We argue that exposures of micro-breccias and frictionite
(=hyalomylonite) in the debris and at the basal shear planes are indispensable as a tool
for identifying giant landslides and distinguishing them from superficially similar
Quaternary glacial deposits. Recognizing these tell-tale petrographic indicators is
crucial, in particular where the scarcity of geomorphic evidence typically used for
detecting large landslides (e.g. displaced ridge lines, cirque-shaped detachment
scars, hummocky terrain, flow lobes, and impounded sediments) may lead to grave
underestimates of both the recurrence and residence time of giant slope failures. |
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