HR: 09:35h
AN: V11B-07    [PDF]
TI: Growth and Collapse of Reunion Island
AU: * L\'{e}nat, J
EM: J.F.Lenat@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, Univ. Blaise Pascal-CNRS-OPGC, 5, rue Kessler, Clermont-Ferrand, 63038 France
AU: Oehler, J
EM: J.F.Oehler@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, Univ. Blaise Pascal-CNRS-OPGC, 5, rue Kessler, Clermont-Ferrand, 63038 France
AU: Labazuy, P
EM: P.Labazuy@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, Univ. Blaise Pascal-CNRS-OPGC, 5, rue Kessler, Clermont-Ferrand, 63038 France
AU: Merle, O
EM: O.Merle@opgc.univ-bpclermont.fr
AF: Laboratoire Magmas et Volcans, Univ. Blaise Pascal-CNRS-OPGC, 5, rue Kessler, Clermont-Ferrand, 63038 France
AB: Rising above a seafloor of Paleocene age, the Reunion oceanic volcanic system is a flattened cone having a basal diameter of 200 to 240 km and height of about 7000 m. The island. has a diameter of 50 to 70 km and reaches 3000 m in height. The dormant Piton des Neiges and the highly active Piton de la Fournaise volcanoes constitute the island, which represents only a small percentage, about 3%, of the volume of the whole system. Bathymetric and sonar surveys of the submarine flanks, as well as gravity, magnetic and seismic surveys inland and offshore, permit to image part of the remaining 97%. Gravity data show the presence of 2 large and deeply rooted dense bodies beneath the center of Piton des Neiges and the eastern coast. These bodies are hypovolcanic complexes that formed during the growth of Piton des Neiges and that of an other, now concealed, main volcanic focus named Les Aliz‚s. The young Piton de la Fournaise volcano has not yet developed a large, dense hypovolcanic complex. The relationship between these large dense bodies and depressions at the surface is being investigated. Available high-precision bathymetric and sonar images of the submarine flanks show that products resulting from flank collapses are present virtually all around the island. At least 15 individual units can be recognized on the surface of the submarine flanks. The dimensions of most units imply large source areas on land. The most recent landslide events that affected Piton de la Fournaise and their source areas on land are well defined. This is not the case for older landslides. On the basis of topographic features and available geological data we have attempted to locate their most probable sources areas. We conclude that the headwalls of several huge landslides intersect in the central area of Piton des Neiges. A unique case of collapse is that of the central area of Piton de la Fournaise. We propose a mechanism of passive collapse of this area in response to the lateral collapse of eastern flank of the edifice.
DE: 1234 Regional and global gravity anomalies and Earth structure
DE: 3022 Marine sediments--processes and transport
DE: 3045 Seafloor morphology and bottom photography
DE: 8424 Hydrothermal systems (8135)
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting