Abstract
AbstractRock avalanches destroy and reshape landscapes in only a few minutes and are among the most hazardous processes on Earth. The surface morphology of rock avalanche deposits and the interaction with the underlying material are crucial for runout properties and reach. Water within the travel path is displaced, producing large impact waves and reducing friction, leading to long runouts. We hypothesize that the 0.2 km3 Holocene Eibsee rock avalanche from Mount Zugspitze in the Bavarian Alps overran and destroyed Paleolake Eibsee and left a unique sedimentological legacy of processes active during the landslide. We captured 9.5 km of electrical resistivity tomography (ERT) profiles across the rock avalanche deposits, with up to 120 m penetration depth and more than 34 000 datum points. The ERT profiles reveal up to ~50 m thick landslide debris, locally covering up to ~30 m of rock debris with entrained fine‐grained sediments on top of isolated remnants of decametre‐wide paleolake sediments. The ERT profiles allow us to infer processes involved in the interaction of the rock avalanche with bedrock, lake sediments, and morainal sediments, including shearing, bulging, and bulldozing. Complementary data from drilling, a gravel pit exposure, laboratory tests, and geomorphic features were used for ERT calibration. Sediments overrun by the rock avalanche show water‐escape structures. Based on all of these datasets, we reconstructed both position and size of the paleolake prior to the catastrophic event. Our reconstruction of the event contributes to process an understanding of the rock avalanche and future modelling and hazard assessment. Here we show how integrated geomorphic, geophysical, and sedimentological approaches can provide detailed insights into the impact of a rock avalanche on a lake. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd
Highlights
No study has documented sedimentology that reveals the spatial and temporal reconstruction of a rock avalanche that has entered a lake and displaced its water. We focus on this issue by presenting evidence for the existence and size of a paleolake in the German Alps that was overrun by a rock avalanche
The results of the complex flow behaviour of the Eibsee rock avalanche can be seen in deposit morphology, bulk material composition related to mixing or entrainment of substrate material and water (ERT), and rock avalanche lithofacies
A bare‐earth digital elevation model (DEM) with 1‐m resolution was provided by the Bavarian Surveying and Mapping Authority (2006)
Summary
Massive rock‐slope failures cause more than 60% of all catastrophic landslide disasters (Evans et al, 2006). The interaction of the rockslide and rock avalanche material with the substrate over which they travel strongly influences runout properties (e.g. Abele, 1994; Hungr and Evans, 2004; Dufresne et al, 2010; Robinson et al, 2015). Erodible and deformable substrates as well as obstacles may divide the rock avalanche into multiple lobes, and their deposits often show complex emplacement structures with longitudinal and transverse ridges (Hewitt, 2006; Dufresne et al, 2015; Dufresne et al, 2016). Large landslides that enter lakes or other water bodies have generated disastrous waves up to several 100 m high (e.g. Lituya Bay; Fritz et al, 2009). Researchers have analysed landslide‐triggered impact waves in the laboratory (e.g. Evers and Hager, 2016; Miller et al, 2017), reconstructed displacement waves by numerical modelling (e.g. Kafle et al, 2016; Gylfadóttir et al, 2017), and provided insights into the sedimentology of impact‐wave deposits (e.g. Roberts et al, 2013; Dufresne et al, 2018)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
