Karrat Fjord tsunamigenic landslide

On 17 June 2017, a landslide-generated tsunami reached the village of Nuugaatsiaq, Greenland, leaving four persons missing and presumed dead. Through a 3D quantitative comparison with pre-failure topography, it was estimated that approximately 58 million m3 of rock and colluvium (talus) was mobilized during the landslide, 45 million m3 of which reached the fjord, resulting in a destructive tsunami. This event was classified as a tsunamigenic extremely rapid rock avalanche which likely released along a pre-existing metamorphic fabric, bounded laterally by slope-scale faults. The Karrat Fjord landslide occurred on a steep, south-facing mountain slope with total vertical relief of greater than 2100 m from sea level to ridgetop, over a horizontal distance of approximately 3100 m. The source area of the landslide was approximately mid-slope, and the material involved both in situ bedrock and colluvium. The slope itself is not glaciated, although adjacent north-facing and sheltered slopes are. Permafrost conditions are unknown. Bedrock geology is high-grade Archean gneiss and overlying paleo-Proterozoic schist and quartzite of the Karrat Group (Mott et al. 2013; Grocott and McCaffrey 2017). These are recognized to have a strong planar metamorphic fabric, related to bedding in the protolithic sedimentary rocks (Mott et al. 2013; Grocott and McCaffrey 2017), and local and regional thrust and extensional faulting are common throughout the area. References: Gauthier, D., Anderson, S.A., Fritz, H.M. et al. Landslides (2018) 15: 327. https://doi.org/10.1007/s10346-017-0926-4