RHUM-RUM (Réunion Hotspot and Upper Mantle & Réunions Unterer Mantel): Seismological imaging of a mantle plume under La Réunion, western Indian Ocean

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The island of La Réunion is one of the most active and long-lived volcanoes in the world. Its well-dated, 5500-km long hotspot track emerges from the Deccan Traps of India, one of the largest flood basalt provinces on earth, which had a massive impact on global climate and life when they erupted. We want to establish the heat source and "plumbing system" that has been fueling this powerful hotspot for 65 million years: Is there a conduit into the deepest mantle (2900 km deep), directly heated by earth's molten core? Is there a connection to the African Superswell at mid-mantle depths? Or could the Réunion hotspot represent a much shallower mechanism? The goal of the RHUM-RUM experiment is to seismically image a mantle plume - or lack of plume - from the surface down to the core-mantle boundary, and to understand the results in terms of material and heat flow. This comprises vertically ascending flow in the plume conduit, as well as any lateral flow spreading into the upper mantle of the western Indian Ocean. We will investigate the long-standing hypothesis that an asthenospheric channel from La Réunion feeds the Central Indian Ridge at 1500 km distance ("plume-ridge interaction"). RHUM-RUM is a German-French collaboration. Jointly we want to deploy 57 ocean-bottom seismometers and 27 land stations over an area of 2000 x 2000 km², making this the largest ocean plume imaging project to date. The data will be analyzed using the most modern, waveform-based imaging methods in seismology.