Giant landslides in the Vaigat strait in Greenland – GWC Mag

The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.

A fascinating and important open access paper has just been published in the journal Geology (Svennevig et al. 2023) that seeks to understand the generation of tsunami waves in high latitude fjord areas, such as Greenland and Alaska. The source of these tsunamis is rock avalanches. In the research, the authors have examined the Vaigat strait in west Greenland, based upon a new subaerial and submarine digital elevation model, supplemented by field mapping and the analysis of seismic data. This approach has allowed the authors to identify rock avalanches from their crown high on the slopes to their deposit within the fjord. The authors have then modelled the potential tsunamis that these events could have generated.

As the image below shows, it is no surprise that large landslides have occurred in this area in the past (this is located at 70.2795, -52.7946]:-

But, when combined with the bathymetry data, the results are stunning. The image below, from (Svennevig et al. 2023), shows the combined data, including the rock avalanche scars and the deposits in the fjord.

In total, Svennevig et al. (2023) have identified nine giant rock avalanches along the vaigat strait. The scale is astonishing – as the authors write, the

“three largest complexes have deposit thicknesses up to 300 m, runout distances reaching 19 km, and best-estimate volumes from 1.7 to 8.4 km³.

The largest of these, the Ujarasussuk rock avalanche, affected an area of 133 km², with a length of 19 km and a width of almost 10 km. The arcuate landslide scar extends from an elevation of 1120 m to a water depth of 523 m. It is not clear as to whether this landslide occurred in a single event or as a sequence of failures, but if it was a single failure then the potential displacement wave would have had a run-up distance of up to 280 m on the opposite shore. Clearly, a repeat of such an event would be a very substantial hazard to anyone or anything in the strait or on the adjacent coasts.

Whilst these landslides have not been dated at present, the sedimentary sequence suggests that they occurred in the early Holocence, when the climate was changing rapidly. Thus, in an era of renewed rapid climatic change, understanding the mechanisms of drivers of these large events is increasingly important.

Reference

Svennevig, K., Owen, M.J., Citterio, M. et al. 2023. Holocene gigascale rock avalanches in Vaigat strait, West Greenland—Implications for geohazard. Geology, https://doi.org/10.1130/G51234.1.

Text © 2023. The authors. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

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