Erosion by the Storm Helena on Basse Terre Island - Guadeloupe: Past Climatic Consequences
Abstract
It is generally accepted that extreme meteorological events are the main morphogenic agents in the tropical belt. In the lesser Antilles arc, these events have an average return period of 4 to 5 years since they are registered. We measured the erosive effects of the tropical storm Helena that hit the volcanic Basse Terre Island (Guadeloupe - Lesser Antilles Arc) on October 24, 1963, on aerial images taken few weeks after the event by the French "Institut Géographique National"(IGN). On the images, 253 landslides, which occured during the storm, were identified and mapped. These landslides were located in the center of the island in the watershed with major relief. If the thickness of the landslide was 1m, i.e. less than the thickness of the weathered layer, the total volume of displaced sediments corresponded to denudation of 1.4mm on the watersheds concerned by landsliding. The total volume of eroded material since the emplacement of lavas has been estimated for each watershed by measuring the volume of valleys. The average velocity of denudation has been estimated to 0.5mm/y since the lava emplacement. If the storm Helena is characteristic of the storms that hit Basse Terre during the Quaternary, the period of return of such extreme meteorological event should be nearer 15 years rather than 4 to 5 years. This longer value of the period of return is coherent with the lower surface temperatures recorded before the Holocene in the Caribbean and Atlantic oceans, which produced less storms then present-day conditions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFMEP53C1041D
- Keywords:
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- 1625 GLOBAL CHANGE / Geomorphology and weathering