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We investigate the temporal gravity changes associated with one of the major recent eruptions at Piton de la Fournaise volcano (March 1998) that occurred after an unusual five‐year quiet period and initiated a new eruptive cycle. Repeated microgravity surveys allowed us to measure residual gravity changes up to 100 μGal within the Enclos Fouqué caldera for four months before the start of the eruption. We first analyzed the temporal gravity changes and the height changes, also measured at the gravity benchmarks, on the basis of an intrusive dyke model previously proposed for this eruption from InSAR and tilt data. This analysis reveals that such simple model (finite rectangular shaped tensile dislocation) cannot fit both gravity and geodetic data and leads us to propose a dual source gravity model for this eruption. The gravity data inversion using a genetic algorithm search method allows us to quantify the mass …