Erosion during Extreme Flood Events Dominates Holocene Canyon Evolution in North-East Iceland
International audience The importance of high-magnitude, short-lived flood events in controlling the evolution of bedrock landscapes is not well understood. During such events, erosion processes can shift from one regime to another upon the passing of thresholds, resulting in abrupt landscape change...
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ftccsdartic:oai:HAL:insu-01088566v1 2023-05-15T16:49:13+02:00 Erosion during Extreme Flood Events Dominates Holocene Canyon Evolution in North-East Iceland Baynes, Edwin ATTAL, Mikaël Dugmore, Andrew Kirstein, Linda Niedermann, Samuel Lague, Dimitri University of Edinburgh Géosciences Rennes (GR) Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1) Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES) San Francisco, United States 2014-12-15 https://hal-insu.archives-ouvertes.fr/insu-01088566 en eng HAL CCSD insu-01088566 https://hal-insu.archives-ouvertes.fr/insu-01088566 AGU Fall Meeting 2014 https://hal-insu.archives-ouvertes.fr/insu-01088566 AGU Fall Meeting 2014, Dec 2014, San Francisco, United States. pp.EP34B-03 [SDU.STU]Sciences of the Universe [physics]/Earth Sciences info:eu-repo/semantics/conferenceObject Conference papers 2014 ftccsdartic 2021-11-28T01:17:56Z International audience The importance of high-magnitude, short-lived flood events in controlling the evolution of bedrock landscapes is not well understood. During such events, erosion processes can shift from one regime to another upon the passing of thresholds, resulting in abrupt landscape changes that can have an important long lasting legacy on landscape morphology.Here we use topographic analysis and cosmogenic 3He surface exposure dating of fluvially sculpted surfaces to determine the timing of extreme flood events within the Jökulsárgljúfur canyon (North-East Iceland) and to constrain the mechanisms of bedrock erosion during these events. Once a threshold flow depth has been exceeded, the dominant erosion mechanism becomes the toppling and transportation of basalt lava columns and erosion occurs through the upstream migration of knickpoints. Surface exposure ages allow identification of three catastrophic erosive flood events about 9, 5 and 2 ka ago when multiple active knickpoints retreated large distances (> 2 km). Despite sustained high discharge of sediment-rich glacial meltwater (ranging from 100 to 500 m3 s-1), there is no evidence for a transition to an abrasion-dominated erosion regime since the last erosive flood event: the vertical knickpoints have not diffused over time and there is no evidence of incision into the canyon floor.We hypothesise that the erosive signature of the extreme events is maintained in this landscape due to the nature of the bedrock, the large scale of the river, large knickpoints and associated plunge pools, and the lack of transported coarse sediment (greater than gravel size). We explore these controls with an experimental study to define the possible influence of the following parameters on the dynamics of knickpoint migration and morphology in a controlled environment: discharge, flow regime, knickpoint height and initial topographic slope. Conference Object Iceland Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Jökulsárgljúfur ENVELOPE(-15.083,-15.083,64.517,64.517) |
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 |
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
spellingShingle |
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences Baynes, Edwin ATTAL, Mikaël Dugmore, Andrew Kirstein, Linda Niedermann, Samuel Lague, Dimitri Erosion during Extreme Flood Events Dominates Holocene Canyon Evolution in North-East Iceland |
topic_facet |
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences |
description |
International audience The importance of high-magnitude, short-lived flood events in controlling the evolution of bedrock landscapes is not well understood. During such events, erosion processes can shift from one regime to another upon the passing of thresholds, resulting in abrupt landscape changes that can have an important long lasting legacy on landscape morphology.Here we use topographic analysis and cosmogenic 3He surface exposure dating of fluvially sculpted surfaces to determine the timing of extreme flood events within the Jökulsárgljúfur canyon (North-East Iceland) and to constrain the mechanisms of bedrock erosion during these events. Once a threshold flow depth has been exceeded, the dominant erosion mechanism becomes the toppling and transportation of basalt lava columns and erosion occurs through the upstream migration of knickpoints. Surface exposure ages allow identification of three catastrophic erosive flood events about 9, 5 and 2 ka ago when multiple active knickpoints retreated large distances (> 2 km). Despite sustained high discharge of sediment-rich glacial meltwater (ranging from 100 to 500 m3 s-1), there is no evidence for a transition to an abrasion-dominated erosion regime since the last erosive flood event: the vertical knickpoints have not diffused over time and there is no evidence of incision into the canyon floor.We hypothesise that the erosive signature of the extreme events is maintained in this landscape due to the nature of the bedrock, the large scale of the river, large knickpoints and associated plunge pools, and the lack of transported coarse sediment (greater than gravel size). We explore these controls with an experimental study to define the possible influence of the following parameters on the dynamics of knickpoint migration and morphology in a controlled environment: discharge, flow regime, knickpoint height and initial topographic slope. |
author2 |
University of Edinburgh Géosciences Rennes (GR) Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Rennes (OSUR)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Rennes 1 (UR1) Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES) |
format |
Conference Object |
author |
Baynes, Edwin ATTAL, Mikaël Dugmore, Andrew Kirstein, Linda Niedermann, Samuel Lague, Dimitri |
author_facet |
Baynes, Edwin ATTAL, Mikaël Dugmore, Andrew Kirstein, Linda Niedermann, Samuel Lague, Dimitri |
author_sort |
Baynes, Edwin |
title |
Erosion during Extreme Flood Events Dominates Holocene Canyon Evolution in North-East Iceland |
title_short |
Erosion during Extreme Flood Events Dominates Holocene Canyon Evolution in North-East Iceland |
title_full |
Erosion during Extreme Flood Events Dominates Holocene Canyon Evolution in North-East Iceland |
title_fullStr |
Erosion during Extreme Flood Events Dominates Holocene Canyon Evolution in North-East Iceland |
title_full_unstemmed |
Erosion during Extreme Flood Events Dominates Holocene Canyon Evolution in North-East Iceland |
title_sort |
erosion during extreme flood events dominates holocene canyon evolution in north-east iceland |
publisher |
HAL CCSD |
publishDate |
2014 |
url |
https://hal-insu.archives-ouvertes.fr/insu-01088566 |
op_coverage |
San Francisco, United States |
long_lat |
ENVELOPE(-15.083,-15.083,64.517,64.517) |
geographic |
Jökulsárgljúfur |
geographic_facet |
Jökulsárgljúfur |
genre |
Iceland |
genre_facet |
Iceland |
op_source |
AGU Fall Meeting 2014 https://hal-insu.archives-ouvertes.fr/insu-01088566 AGU Fall Meeting 2014, Dec 2014, San Francisco, United States. pp.EP34B-03 |
op_relation |
insu-01088566 https://hal-insu.archives-ouvertes.fr/insu-01088566 |
_version_ |
1766039380317700096 |