Hydrologic and thermal modeling of an active volcano: the Piton de la Fournaise, Reunion
Abstract
The hydrology of active volcanic islands and the interactions between cold groundwater flow and hot magmatic fluids are, as yet, poorly understood. In this study of the Piton de la Fournaise, Reunion, we try to estimate the different terms in the hydrologic balance and describe the nature and importance of groundwater flow in an active volcano. A challenging aspect of this study was that only limited data were available, a common feature of such systems. There were some volcanologic data, few hydrologic data and a deep geothermal borehole where a thermal profile had been established. First, we develop a global hydrologic model of the Piton de la Fournaise by making certain assumptions concerning groundwater pathways. This model is calibrated on the available hydrologic data. We then build a thermal model of the volcano based on hypotheses of its internal structure and on the groundwater flow pattern derived from the first model. This model is fitted on the thermal profile. We conclude that groundwater flow inside the volcano can be described as a succession of local perched aquifers, which eventually release water to a continuous basal aquifer close to the coast, with diffuse outlets to the ocean. The infiltrating water is kept away from the magma chamber by a thick impervious shell surrounding the chamber, probably created by silica precipitation in the fractured basalt. Heat is essentially conveyed to the ocean by groundwater flow. This model is likely to be valid for other active hot-spot volcanoes.
- Publication:
-
Journal of Hydrology
- Pub Date:
- April 1997
- DOI:
- 10.1016/S0022-1694(96)03071-5
- Bibcode:
- 1997JHyd..191...37V