Other
Scientific paper
Apr 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994e%26psl.122..291g&link_type=abstract
Earth and Planetary Science Letters (ISSN 0012-821X), vol. 122, no. 3-4, p. 291-302
Other
19
Calderas, Geomorphology, Structural Properties (Geology), Volcanoes, Volcanology, Collapse, Evolution (Development), Landslides, Models
Scientific paper
Reunion Island is an intraplate volcano linked with the hot spot activity that is also responsible for the volcanism of Mauritius and of the Mascarene Plateau. It is composed of two main volcanic complexes, the Piton des Neiges and the still active Piton de la Fournaise. The latter exhibits a special morphostructural evolution characterized by successive nested U-shaped calderas that open seaward. We propose an analysis of this evolution which permits us to deduce a model which can be extended to the general history of the island. From the morphology of the youngest caldera on the one hand and from the K-Ar data on the cliffs corresponding to the successive rims on the other we established the frequency of landslide collapses and estimate the volumes emitted during each successive phase. This yields evidence of an increasing disequilibrium of the southeastern flank of Piton de la Fournaise. Indeed, through time the frequency of collapses increases and collapse volume decreases. We model the phenomenon with an exponentially smoothed sinusoidal curve, with time on the abscissa and eruptive output on the ordinate. Each maximum on the curve corresponds to the successive slumps and the area of each arch represents the volume erupted during each phase. This can be extrapolated to the earlier volcanic history of Reunion, setting the first collapse at about 1.8 Ma, which affected the main part of the present island, preserving only the Masiff de la Montagne at its north-northwestern end. This explains the breccias observed in the deep erosional features of the massif of the Piton des Neiges and takes into account the lack of lavas with dates between 1.8 and 1.1 Ma. Comparison between the curve of emissivity and the total volume estimated for the whole island volcano yields an age of 5 Ma for the beginning of the activity. This age coincides with the end of the main volcanic activity in Mauritius.
Gillot Pierre-Yves
Lefèvre Jean-Claude
Nativel Pierre-Edouard
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