Frequency of rockfalls in the permafrost-affected rock walls of the Mont Blanc massif in relation with post-glacial warm periods
Poster The characterization of the evolution of rockfall (> 100 m3) in high mountain areas is a prerequisite to any risk management. This study aimed to collect and analyse data on past rockfall in the Mont Blanc massif in order to investigate the possible correlation between periods of warming a...
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ftccsdartic:oai:HAL:halsde-00867033v1 2023-05-15T16:37:40+02:00 Frequency of rockfalls in the permafrost-affected rock walls of the Mont Blanc massif in relation with post-glacial warm periods Ravanel, Ludovic Egli, Markus Brandova, D. Kubik, P. Deline, Philip Gruber, S. Environnements, Dynamiques et Territoires de la Montagne (EDYTEM) Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS) Department of Geography Universität Zürich Zürich (UZH) Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich) Paris, France 2013-08-27 https://hal.archives-ouvertes.fr/halsde-00867033 en eng HAL CCSD halsde-00867033 https://hal.archives-ouvertes.fr/halsde-00867033 8th International Conference (IAG) on Geomorphology https://hal.archives-ouvertes.fr/halsde-00867033 8th International Conference (IAG) on Geomorphology, Aug 2013, Paris, France [SDE.ES]Environmental Sciences/Environmental and Society info:eu-repo/semantics/conferenceObject Conference papers 2013 ftccsdartic 2021-11-07T04:34:04Z Poster The characterization of the evolution of rockfall (> 100 m3) in high mountain areas is a prerequisite to any risk management. This study aimed to collect and analyse data on past rockfall in the Mont Blanc massif in order to investigate the possible correlation between periods of warming and rockfall and, beyond, between permafrost degradation and rockfall. This required to compile exhaustive inventories and to compare them with climatic data. We first documented the occurrence of the 58 rockfalls at the Drus and the Aiguilles de Chamonix, documented by photo-comparison since the end of the Little Ice Age (LIA) and direct observation in the recent period. We then crossed these rockfall data with available climate data. In the West face of the Drus, air temperature seems to control the triggering of the 12 documented rockfalls, as suggests by their concomitance with the hottest periods. The main one (2005, 265 000 m3) seems to have been promoted by the combination of heat and heavy rainfalls, resulting in high fluid pressure in the rock fractures. Surface runoff has been observed in the scar of this event and massive ice was also observed after the rockfall of October 2011. The role of climate is also demonstrated by the analysis of the 46 rockfalls documented on the North side of the Aiguilles de Chamonix after the LIA, with a very strong correlation between these and the hottest periods: 70 % of the rockfalls occurred during the past two decades, characterized by the increasing global warming. Heat waves are particularly prone to rockfall: the maximum rockfall frequency occurred during the 2003 Summer heat wave. To investigate beyond the last century and a half, we carried out surface exposure dating on 20 samples of granite from 6 rockwalls of the massif by the determination of 10Be-concentrations in their surface. The surface ages found vary from less than a few hundred years to tens of thousands years. These dates are generally corresponding to warm periods. Conference Object Ice permafrost Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Drus ENVELOPE(141.579,141.579,-66.769,-66.769) Mont Blanc ENVELOPE(69.468,69.468,-49.461,-49.461) |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
[SDE.ES]Environmental Sciences/Environmental and Society |
spellingShingle |
[SDE.ES]Environmental Sciences/Environmental and Society Ravanel, Ludovic Egli, Markus Brandova, D. Kubik, P. Deline, Philip Gruber, S. Frequency of rockfalls in the permafrost-affected rock walls of the Mont Blanc massif in relation with post-glacial warm periods |
topic_facet |
[SDE.ES]Environmental Sciences/Environmental and Society |
description |
Poster The characterization of the evolution of rockfall (> 100 m3) in high mountain areas is a prerequisite to any risk management. This study aimed to collect and analyse data on past rockfall in the Mont Blanc massif in order to investigate the possible correlation between periods of warming and rockfall and, beyond, between permafrost degradation and rockfall. This required to compile exhaustive inventories and to compare them with climatic data. We first documented the occurrence of the 58 rockfalls at the Drus and the Aiguilles de Chamonix, documented by photo-comparison since the end of the Little Ice Age (LIA) and direct observation in the recent period. We then crossed these rockfall data with available climate data. In the West face of the Drus, air temperature seems to control the triggering of the 12 documented rockfalls, as suggests by their concomitance with the hottest periods. The main one (2005, 265 000 m3) seems to have been promoted by the combination of heat and heavy rainfalls, resulting in high fluid pressure in the rock fractures. Surface runoff has been observed in the scar of this event and massive ice was also observed after the rockfall of October 2011. The role of climate is also demonstrated by the analysis of the 46 rockfalls documented on the North side of the Aiguilles de Chamonix after the LIA, with a very strong correlation between these and the hottest periods: 70 % of the rockfalls occurred during the past two decades, characterized by the increasing global warming. Heat waves are particularly prone to rockfall: the maximum rockfall frequency occurred during the 2003 Summer heat wave. To investigate beyond the last century and a half, we carried out surface exposure dating on 20 samples of granite from 6 rockwalls of the massif by the determination of 10Be-concentrations in their surface. The surface ages found vary from less than a few hundred years to tens of thousands years. These dates are generally corresponding to warm periods. |
author2 |
Environnements, Dynamiques et Territoires de la Montagne (EDYTEM) Université Savoie Mont Blanc (USMB Université de Savoie Université de Chambéry )-Centre National de la Recherche Scientifique (CNRS) Department of Geography Universität Zürich Zürich (UZH) Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich) |
format |
Conference Object |
author |
Ravanel, Ludovic Egli, Markus Brandova, D. Kubik, P. Deline, Philip Gruber, S. |
author_facet |
Ravanel, Ludovic Egli, Markus Brandova, D. Kubik, P. Deline, Philip Gruber, S. |
author_sort |
Ravanel, Ludovic |
title |
Frequency of rockfalls in the permafrost-affected rock walls of the Mont Blanc massif in relation with post-glacial warm periods |
title_short |
Frequency of rockfalls in the permafrost-affected rock walls of the Mont Blanc massif in relation with post-glacial warm periods |
title_full |
Frequency of rockfalls in the permafrost-affected rock walls of the Mont Blanc massif in relation with post-glacial warm periods |
title_fullStr |
Frequency of rockfalls in the permafrost-affected rock walls of the Mont Blanc massif in relation with post-glacial warm periods |
title_full_unstemmed |
Frequency of rockfalls in the permafrost-affected rock walls of the Mont Blanc massif in relation with post-glacial warm periods |
title_sort |
frequency of rockfalls in the permafrost-affected rock walls of the mont blanc massif in relation with post-glacial warm periods |
publisher |
HAL CCSD |
publishDate |
2013 |
url |
https://hal.archives-ouvertes.fr/halsde-00867033 |
op_coverage |
Paris, France |
long_lat |
ENVELOPE(141.579,141.579,-66.769,-66.769) ENVELOPE(69.468,69.468,-49.461,-49.461) |
geographic |
Drus Mont Blanc |
geographic_facet |
Drus Mont Blanc |
genre |
Ice permafrost |
genre_facet |
Ice permafrost |
op_source |
8th International Conference (IAG) on Geomorphology https://hal.archives-ouvertes.fr/halsde-00867033 8th International Conference (IAG) on Geomorphology, Aug 2013, Paris, France |
op_relation |
halsde-00867033 https://hal.archives-ouvertes.fr/halsde-00867033 |
_version_ |
1766027977267609600 |