Abstract
AbstractThe ~0.2 km3 Eibsee rock avalanche impacted Paleolake Eibsee and completely displaced its waters. This study analyses the lake impact and the consequences, and the catchment response to the landslide. A quasi‐3D seismic reflection survey, four sediment cores from modern Lake Eibsee, reaching far down into the rock avalanche mass, nine radiocarbon ages, and geomorphic analysis allow us to distinguish the main rock avalanche event from a secondary debris avalanche and debris flow. The highly fluidized debris avalanche formed a megaturbidite and multiple swashes that are recorded in the lake sediments. The new calibrated age for the Eibsee rock avalanche of ~4080–3970 cal yr BP indicates a coincidence with rockslides in the Fernpass cluster and subaquatic landslides in Lake Piburg and Lake Plansee, and raises the possibility that a large regional earthquake triggered these events. We document a complex history of erosion and sedimentation in Lake Eibsee, and demonstrate how the catchment response and rebirth of the lake are revealed through the complementary application of geophysics, sedimentology, radiocarbon dating, and geomorphology. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd
Highlights
Massive rock‐slope failures often occur progressively in multiple stages from the same scarps or nearby scarps
Our study addresses five research questions: Is the Eibsee rock avalanche a single failure, or can we decipher multistage events? What happens during and after the impact of the rock avalanche on the lake? Does a new lake form, and if so, how and where? Can we find evidence of a displaced paleolake in the modern lake? And, what can we learn about progressive scarp evolution and repeated rock‐slope failures that feature consecutive rock avalanche and debris flow events?
Subunit II can be subdivided in lower (IIa) occurs in sediment pockets on top of unit I characterized by chaotic or transparent seismic facies and has, when compared to the western basins (Figures 2a and 3a), lower amplitudes on top
Summary
Massive rock‐slope failures often occur progressively in multiple stages from the same scarps or nearby scarps. Refining recurrence rates and magnitudes is essential for future hazard assessment, and improving our understanding of progressive failure and catchment response after such catastrophic events. The so‐called ‘Fernpass rockslide cluster’ is a group of large rock‐slope failures in the Northern Calcareous Alps and Central Eastern Alps (Figure 1a; Prager et al, 2008). Many of these landslides occurred at or after the end of the Holocene climate optimum during the Subboreal (~4800–3800 cal yr BP; Wanner et al, 2008, 2011). A new complementary approach is required to decipher the multistage character of ancient events
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