Other meanings of Réunion hotspot
Geology
The Réunion hotspot is a volcanic hotspot located in the Indian Ocean, currently beneath Réunion Island. It has generated a long chain of volcanic features, including the Deccan Traps flood basalts and the Chagos-Laccadive Ridge, and remains an important subject for studying mantle plumes and plate tectonics.
The Réunion hotspot is currently positioned beneath Réunion Island in the western Indian Ocean, about 700 km east of Madagascar. It lies within the Somali Plate, part of the diverging boundary between the African and Indo-Australian plates. The hotspot is thought to be a mantle plume, a narrow upwelling of hot material from deep within Earth's mantle, which melts to produce basaltic magmas as the lithosphere moves over it. The current expression includes the active volcano Piton de la Fournaise, one of the most active shield volcanoes on Earth.1
As the Indian Plate moved northward over the past 66 million years, the hotspot produced a trail of volcanic islands and seamounts. The trail includes the Chagos-Laccadive Ridge, the Maldives, and the Mascarene Plateau, with ages progressing from the Deccan Traps in India to Réunion. The Deccan Traps, erupted around 66 million years ago, are one of the largest flood basalt provinces on Earth, covering over 500,000 square kilometers. This eruption coincided with the Cretaceous-Paleogene boundary and is implicated in the mass extinction event, though the Chicxulub impact is the primary cause.2 The hotspot trail also includes the Nazareth and Saya de Malha banks, now submerged, indicating a long history of volcanism that has subsided as the oceanic crust cooled.3
The Réunion hotspot produces predominantly tholeiitic basalts, similar to other ocean island basalts, but with distinct isotopic signatures. Geochemical analyses reveal a primitive mantle source with a high 3He/4He ratio, suggesting a deep, relatively undegassed reservoir. The plume may ascend from the core-mantle boundary, as seismological studies indicate a low-velocity zone in the lower mantle beneath the region. The composition of lavas from Piton de la Fournaise and Piton des Neiges shows variations over time, reflecting changes in melting depth and source heterogeneity.4 These studies help constrain the thermal structure of the mantle and the dynamics of plumes.
While the main trail is well known, the hotspot also produced the Lakshadweep islands, the southernmost part of the Chagos-Laccadive Ridge. The hotspot's track includes a prominent bend near the southern tip of India, corresponding to a change in plate motion around 80 million years ago. The volcanic rocks of the Deccan Traps have been studied for their platinum group element content, which shows no significant enrichment, suggesting the eruption did not directly contribute to the extinction through metal toxicity. Additionally, the island of Rodrigues, at the eastern end of the Mascarene Plateau, may be a recent expression of the hotspot, though its volcanism is much younger than Réunion's main shield building. The exact relationship between the Réunion hotspot and the Mauritius microcontinent, a fragment of continental crust buried beneath the island, remains a topic of research.5
This article focuses on the Réunion hotspot as a volcanic source; for the island itself, see Réunion.
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