Paraglacial Rock-Slope Failure Following Deglaciation in Western Norway

Abstract

The paraglacial framework describes the geomorphological response to glaciation and deglaciation, whereby non-renewable, metastable, glacially-conditioned sediment sources are progressively released by a range of nonglacial processes. These include slope failures that directly modify the bedrock topography of mountain landscapes. This chapter synthesises recent research on the paraglacial evolution of western Norway's mountain rock-slopes, and evaluates the importance of glaciation, deglaciation, and associated climatic and non-climatic processes. Following an introduction to the concept of paraglacial landscape change, current understanding of rock-slope responses to deglaciation are outlined, focussing on the spatial distribution, timing, duration and causes of rock-slope failure activity. Preliminary analysis of an inventory of published ages for 49 prehistoric, moderate-large (>10 3 m 3 ) rock-slope failures (RSFs) indicates that the great majority occurred in the Late Weichselian / Early Holocene transition (~13-9 ka), within 2 ka of deglaciation. Subsequent RSFs were much smaller, though event frequency increased again at 8-7 ka and 5-4 ka BP. The majority of RSFs were not directly triggered by deglaciation (debuttressing) but were preconditioned for more than 1000 years after ice withdrawal, until slopes collapsed. It is proposed that the primary causes of failure within 2 ka of ice retreat were stress redistribution, subcritical fracture propagation, with some events possibly triggered by seismic activity. While earthquakes may have triggered renewed failure of rock-slopes in the Late Holocene, it seems likely that permafrost degradation and water supply were locally important. Priority avenues for further research are briefly identified.

Geochemistry of Antarctic periglacial soils from Harmony Point, Nelson Island

“…After the cumulative climate changes in Maritime Antarctica, the last glacier retreat of the previously ice-covered zones (Goryachkin et al 1999;Francelino et al 2011;Rangwala and Miller 2012;Moura et al 2012;Oliva et al 2018;Curry 2021) enabled newly exposed ice-free areas to develop different soils and vegetation (Kabała and Zapart 2012;Heckmann et al 2016;Milner et al 2017;Oliva et al 2019). In Maritime Antarctica (MA), the most intense deglaciation occurred at 5000-4000 years ago (Björck et al 1991Björck and Zale 1996), and triggered the formation of most soils now described, some of which are very atypical (Campbell and Claridge 1987;Bockheim 2005;Lopes et al 2019;Almeida et al 2021).…”