Flank landslides on Reunion Island volcanoes (Indian Ocean): Evidence, implications and origins

• Main Author: Oehler, Jean-François
• Other Authors: Laboratoire Magmas et Volcans (LMV), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Université Blaise Pascal - Clermont-Ferrand II, Lénat Jean-François([e-mail])
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2005
• Subjects: Reunion Island; flank landslides; debris avalanches; multibeam bathymetry and backscatter data; digital elevation model (DEM); James Ross Island; low strength layers; analogue modeling; oceanic island evolution model; Ile de La Réunion; déstabilisations de flanc; avalanches de débris; bathymétrie et imagerie acoustique multifaisceaux; modèles numériques de terrain (MNT); Ile de James Ross; plans de faible résistance; modélisations analogiques; modèle d'évolution des îles océaniques; [SDU.STU.AG]Sciences of the Universe [physics]/Earth Sciences/Applied geology; [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; Ross Island
• Online Access: https://theses.hal.science/tel-00010498; https://theses.hal.science/tel-00010498/document; https://theses.hal.science/tel-00010498/file/tel-00010498.pdf

Composition du jury de thèse: Olivier Merle, Président, Université Blaise Pascal, Clermont II Christine Deplus, Examinateur, Institut de Physique du Globe de Paris Patrick Bachèlery, Rapporteur, Université de La Réunion Bruno Savoye, Rapporteur, IFREMER -- La version de la thèse déposée en ligne est une version basse résolution. Pour une version haute résolution, me contacter à: [e-mail] The joint study of the emerged and submerged parts of Reunion Island (Indian Ocean), based on the evaluation of marine multibeam data collected these last 20 years and confronted with previous geological and geophysical works, demonstrates the considerable importance of flank landslide processes in the evolution of this volcanic oceanic system. Fifty or so mass-wasting events recurrently dismantled Piton des Neiges, Les Alizés, and Piton de La Fournaise volcanoes during the last 2 million years at least. They are multi-scale, primary or secondary, and of aerial, coastal or submarine origin. Most correspond to instantaneous and catastrophic phenomena of debris avalanche type. Their deposits are mainly accumulated at sea, within four gigantic topographic bulges named "Reliefs Sous-Marins", located to the east, north, west and south of the island. These fans are 20-30 km wide at the coastline and 100-150 km wide at their end, 70-80 km offshore. They were built gradually by the superimposition and/or the juxtaposition of products displaced during landslide episodes implying up to several hundreds of km3 of materials. A very small proportion is recognized on land, in Piton des Neiges central part or at its littoral edges, and constitutes the proximal facies of the deposits recognized offshore. The main structural features of Reunion sub-aerial morphology are interpreted as (1) relatively recent landslide scars, often remodelled by erosion and/or filled by subsequent volcanic activity, or (2) remnants of old debris avalanches amphitheatres whose border faults could have been reactivated by volcano-tectonics (caldera ...