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Migrating boulders on the surface of Alpine valley glaciers


Alean, Jürg; Schwendener, Lea; Zemp, Michael (2020). Migrating boulders on the surface of Alpine valley glaciers. Geografiska Annaler: Series A, Physical Geography:Epub ahead of print.

Abstract

Boulders in the ablation areas of Alpine valley glaciers were found to not travel along with the ice in a passive manner only. Many show an additional but smaller component of movement towards the south. We investigate this phenomenon and its governing processes using field observations and measurements from terrestrial and aerial photographs of glaciers in the Swiss Alps. We found that large boulders can migrate from their medial moraine due to cyclic formation of classical glacier tables and also a similar process that produces ice tails. The main driving factors behind boulder migration are the size (and shape) of the boulder, ablation, radiation, and surface slope. On glaciers roughly oriented to the east or west, these processes result in a sorting of boulders from the supraglacial moraine towards the southern side, i.e. towards the sun. Future studies complementing our approach using a differential global positioning system should be able to better distinguish between the velocity components of ice flow and boulder migration, determine the precise azimuth of the latter, and investigate the potential influence on photogrammetric feature tracking.

Abstract

Boulders in the ablation areas of Alpine valley glaciers were found to not travel along with the ice in a passive manner only. Many show an additional but smaller component of movement towards the south. We investigate this phenomenon and its governing processes using field observations and measurements from terrestrial and aerial photographs of glaciers in the Swiss Alps. We found that large boulders can migrate from their medial moraine due to cyclic formation of classical glacier tables and also a similar process that produces ice tails. The main driving factors behind boulder migration are the size (and shape) of the boulder, ablation, radiation, and surface slope. On glaciers roughly oriented to the east or west, these processes result in a sorting of boulders from the supraglacial moraine towards the southern side, i.e. towards the sun. Future studies complementing our approach using a differential global positioning system should be able to better distinguish between the velocity components of ice flow and boulder migration, determine the precise azimuth of the latter, and investigate the potential influence on photogrammetric feature tracking.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Geography
Dewey Decimal Classification:910 Geography & travel
Scopus Subject Areas:Social Sciences & Humanities > Geography, Planning and Development
Physical Sciences > Geology
Uncontrolled Keywords:Geography, Planning and Development, Geology
Language:English
Date:20 December 2020
Deposited On:17 Feb 2021 15:25
Last Modified:18 Feb 2021 21:00
Publisher:Wiley-Blackwell Publishing, Inc.
ISSN:0435-3676
OA Status:Hybrid
Publisher DOI:https://doi.org/10.1080/04353676.2020.1850064

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