The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
Rock avalanches are an important hazard in areas with fjord topography, potentially impacting humans directly but also having the capability to generate large tsunamis that can cause damage over quite large distances. In recent years, there have been efforts to understand this risk in Norway, Alaska and elsewhere.
A really interesting open access paper (Matthew et al. 2024) has just been published in the journal Landslides that examines evidence for rock avalanche occurrence in NE. Baffin Island, an area with classic fjord terrain. Parts of this area, which extends over 60,000 km2, has all of the characteristics that would imply high rock avalanche potential – steep fjord walls, recent deglaciation, seismic hazard and a warming trend in recent decades. Tus, one would expect to see a significant number of rock avalanche scars and deposits in the landscape.
Matthew et al. (2024) have generated an inventory of rock avalanches across this area. The results are very surprising – only eight rock avalanches were identified. This is an example from the paper:-
One of the rock avalanches mapped by Matthew et al. (2020) in NE Baffin Island.
This number of rock avalanches is substantially lower than have been observed in other areas with similar terrain, such Norway and Greenland. The key question that thus emerges is why NE. Baffin Island appears to be behaving differently to those other locations.
Three possibilities emerge. The first is that the study may have missed some of the landslides, most notably because of a lack of bathymetric data that would allow deposits to be identified on the fjord bed. This may be a factor, but is unlikely to be the key cause of the anomalous behaviour.
Second,Matthew et al. (2024) suggest that this area would have experienced a high level of rock avalanche activity in the period immediately after deglaciation, in common with other locations, but that most of the deposits and scars have now been removed. It is thought that the temporal incidence of rock avalanches since this period would be low in most landscapes, but that this has been interrupted more recently through the effects of warming, and the consequent permafrost degradation, which has greatly increased rock avalanche activity in recent decades in other environments. The authors hypothesise that this increase in permafrost degradation has yet to get under way in NE Baffin Island, and thus rock avalanche occurrence remains low for now.
The third possibility, which may be acting in concert with the above, is that the stability of the rock mass is higher in NE Baffin Island than is the case elsewhere. Detailed field investigations would allow this to be analysed in more detail.
This is a really interesting study that lays the foundations for more detailed investigations in this area. Understanding why NE Baffin Island is behaving in manner that appears to be anomalous will shed further light on the controls on rack avalanches in fjords. This is of great importance given the hazards that they pose.
Reference
https://doi.org/10.1007/s10346-024-02315-8Matthew, M.C., Gosse, J.C., Hermanns, R.L. et al. 2024. Rock avalanches in northeastern Baffin Island, Canada: understanding low occurrence amid high hazard potential. Landslides. https://doi.org/10.1007/s10346-024-02315-8.
Text © 2023. The authors. CC BY-NC-ND 3.0Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.
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