Mass Movements in Periglacial Environments

Stoffel, Markus; Huggel, Christian

doi:10.1002/9781118786352.wbieg0815

Cited by 2 publications

(1 citation statement)

References 9 publications

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“…This difference can reflect sensitivity to observation time scales and/or different erosional processes at work. For example, in glaciated landscapes, glaciers not only increase erosion rates during glaciation, but they can result in a postglacial increase in rates that decays over time scales of 10 1 -10 4 yr (Stoffel and Huggel, 2017). Below, we discuss potential sources of this observed difference in short-and long-term retreat rates.…”

Section: Comparison Of Wall Retreat Ratesmentioning

confidence: 99%

Temporal variations in rockfall and rock-wall retreat rates in a deglaciated valley over the past 11 k.y.

Mohadjer

Ehlers

Nettesheim

et al. 2020

Geology

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This study addresses the temporal variations in rockfall activity in the 5.2 km2 calcareous cliffs of the deglaciated Lauterbrunnen Valley, Switzerland. We did this using 19 campaigns of repeated terrestrial laser scans (TLS) over 5.2 yr, power-law predicted behavior from extrapolation of the TLS-derived frequency-magnitude relationship, and estimates of long-time-scale (∼11 k.y.) activity based on the volume of preserved postglacial rockfall talus. Results from the short-time-scale observations indicate no statistically significant difference between TLS observations averaging over 1.5 versus 5.2 yr. Rock-wall retreat rates in both cases are 0.03–0.08 mm/yr. In contrast, the power-law predicted rock-wall retreat rates are 0.14–0.22 mm/yr, and long-term rates from talus volumes are 0.27–0.38 mm/yr. These results suggest (1) short (1.5 yr) TLS inventories of rockfalls provide (within uncertainties) similar frequency-magnitude relationships as longer (5.2 yr) inventories, thereby suggesting short observation periods may be sufficient for hazard characterization from TLS, and (2) higher rock-wall retreat rates over long time scales (Holocene averaged) may reflect debuttressing and stress relaxation effects after glacial retreat, and/or enhanced rockfall activity under periglacial (climatic) conditions.

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Section: Comparison Of Wall Retreat Ratesmentioning

confidence: 99%

Temporal variations in rockfall and rock-wall retreat rates in a deglaciated valley over the past 11 k.y.

Mohadjer

Ehlers

Nettesheim

et al. 2020

Geology

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Ground thermal and geomechanical conditions in a permafrost-affected high-latitude rock avalanche site (Polvartinden, northern Norway)

et al. 2018

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Abstract. On 26 June 2008, a rock avalanche detached in the northeast facing slope of Polvartinden, a high-alpine mountain in Signaldalen, northern Norway. Here, we report on the observed and modelled past and present near-surface temperature regime close to the failure zone, as well as on a subsequent simulation of the subsurface temperature regime, and on initial geomechanical mapping based on laser scanning. The volume of the rock avalanche was estimated to be approximately 500 000 m3. The depth to the actual failure surface was found to range from 40 m at the back of the failure zone to 0 m at its toe. Visible in situ ice was observed in the failure zone just after the rock avalanche. Between September 2009 and August 2013, ground surface temperatures were measured with miniature temperature data loggers at 14 different localities, close to the original failure zone along the northern ridge of Polvartinden and on the valley floor. The results from these measurements and from a basic three-dimensional heat conduction model suggest that the lower altitudinal limit of permafrost at present is at 600–650 m a.s.l., which corresponds to the upper limit of the failure zone. A coupling of our in situ data with regional climate data since 1958 suggests a general gradual warming and that the period with highest mean near surface temperatures on record ended four months before the Signaldalen rock avalanche detached. A comparison with a transient permafrost model run at 10 m depth, representative for areas where snow accumulates, strengthen these findings, which are also in congruence with measurements in nearby permafrost boreholes. It is likely that permafrost in and near the failure zone is presently subject to degradation. This degradation, in combination with the extreme warm year antecedent to the rock failure, is seen to have played an important role in the detaching of the Signaldalen rock avalanche.

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Mass Movements in Periglacial Environments

Cited by 2 publications

References 9 publications

Temporal variations in rockfall and rock-wall retreat rates in a deglaciated valley over the past 11 k.y.

Temporal variations in rockfall and rock-wall retreat rates in a deglaciated valley over the past 11 k.y.

Ground thermal and geomechanical conditions in a permafrost-affected high-latitude rock avalanche site (Polvartinden, northern Norway)

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