The periglacial engine of mountain erosion – Part 2: Modelling large-scale landscape evolution
There is growing recognition of strong periglacial control on bedrock erosion in mountain landscapes, including the shaping of low-relief surfaces at high elevations (summit flats). But, as yet, the hypothesis that frost action was crucial to the assum...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2015-10-01
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| Series: | Earth Surface Dynamics |
| Online Access: | http://www.earth-surf-dynam.net/3/463/2015/esurf-3-463-2015.pdf |
| Summary: | There is growing recognition of strong periglacial control
on bedrock erosion in mountain landscapes, including the
shaping of low-relief surfaces at high elevations (summit
flats). But, as yet, the hypothesis that frost action was
crucial to the assumed Late Cenozoic rise in erosion rates
remains compelling and untested. Here we present a landscape evolution model
incorporating two key periglacial processes – regolith
production via frost cracking and sediment transport via
frost creep – which together are harnessed to variations in
temperature and the evolving thickness of sediment
cover. Our computational experiments time-integrate the
contribution of frost action to shaping mountain
topography over million-year timescales, with the primary
and highly reproducible outcome being the development of
flattish or gently convex summit flats. A simple scaling
of temperature to marine δ<sup>18</sup>O records spanning the past 14 Myr indicates that the highest summit flats in mid- to
high-latitude mountains may have formed via frost action
prior to the Quaternary. We suggest that deep cooling in
the Quaternary accelerated mechanical weathering globally by
significantly expanding the area subject to
frost. Further, the inclusion of subglacial erosion
alongside periglacial processes in our computational
experiments points to alpine glaciers increasing the
long-term efficiency of frost-driven erosion by steepening hillslopes. |
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| ISSN: | 2196-6311 2196-632X |