From mass extinction to island creation
The Piton de la Fournaise, or "Peak of the Furnace," is one of the world's most active volcanoes, erupting on average every nine months. It rises 2,632 meters (8,635 feet) on the eastern side of Réunion Island and is the current surface part of a deep mantle plume that has been active for over 66 million years. This stationary column of hot rock rising from the Earth's mantle has a history linked to both a mass extinction event and the creation of numerous islands across the Indian Ocean.
Around 66 million years ago, as the Indian tectonic plate drifted northward, it passed over this hotspot. The encounter triggered a monumental flood basalt eruption, creating a massive volcanic province known as the Deccan Traps in what is now west-central India. Over a period that may have been as short as 30,000 years, successive lava flows blanketed an area originally estimated at 1.5 million square kilometers, with a total lava volume of about 1 million cubic kilometers. Today, the traps still cover 500,000 square kilometers with a thickness of over 2,000 meters in some places. The eruption coincided with the Cretaceous-Paleogene boundary, and the vast quantities of volcanic gases released are often cited as a cause, alongside the Chicxulub asteroid impact, in the mass extinction that eliminated the dinosaurs.
A trail of volcanic islands
After the Indian plate moved on, the hotspot remained fixed, and the African plate began to drift over it. The plume continued to punch through the oceanic crust, creating a chain of volcanoes. This volcanic track forms the Mascarene Plateau. The oldest parts of this chain, created between 60 and 45 million years ago, include the foundations of the Laccadive Islands, the Maldives, and the Chagos Archipelago.
As the African plate continued its slow northeastern movement, the hotspot's activity built the Saya de Malha Bank around 45 million years ago, followed by the Nazareth and Cargados Carajos Banks. Later, it formed the Mascarene Islands. Mauritius, the oldest of the main islands, emerged between 8 and 10 million years ago. Réunion itself is the youngest part of the chain, having formed in the last two million years. Piton de la Fournaise is the currently active shield volcano on the island, built over 530,000 years from fluid basaltic lava flows. Its structure is dominated by the Enclos Fouqué, a large U-shaped caldera that funnels most lava flows harmlessly towards the sea.