Together with the older Piton des Neiges massif, it forms the island of La Réunion as we see it today. Piton de la Fournaise covers one-third of the island.
The Piton de la Fournaise forms the currently active part of a larger shield volcano: the Piton de la Fournaise massif, whose oldest known rocks were formed around 530,000 years ago. 150,000 years ago, the Piton de La Fournaise was sliding eastwards. 40,000 years ago, the Plaine des Sables collapsed. The Piton de la Fournaise as we know it today dates back some 4,700 years. This age corresponds to the major collapse that gave rise to the caldera, also known as the Fouqué enclosure, accompanied by cataclysmic explosions. The outline of the collapse is still clearly visible in the landscape, forming a continuous cliff 150 to 200 metres high. Subsequent eruptions have reconstituted the central cone of the Piton de la Fournaise, the Dolomieu crater, at the center of the collapse zone.
The rash
Volcanic eruptions are caused by the accumulation of gas in the magma. When the quantity of gas reaches a significant level, it rises into the lithosphere, releasing the molten magma. The Piton de la Fournaise then produces a highly fluid lava that flows over large areas, known as an effusive volcano. The flows that descend the volcano’s slopes can take two different forms, typical of basaltic volcanism: they can be smooth or scree-like. Initially, they are lava of the same composition. If the flow is smooth, the lava remains smooth on the surface and, as it cools, forms drapery-like patterns (known as corded lava). If the flow is rougher, the release of gases forms a kind of “foam” of irregular blocks on the surface: gratons.
The speed at which a flow advances depends on the flow rate and the slope. However, as the flow front solidifies on contact with the cold ground, it can only progress relatively slowly. On the other hand, once a flow has traced its path, the lava can travel at high speed (several tens of km/h).
Some flows reach the shore and flow into the ocean. The lava that continues to flow and slump underwater cools, forming pillow lavas, while a rocky platform gradually builds up, enlarging the island’s land contour. After the eruption of April 2007, 45 hectares of new land were “reclaimed” from the water.
Piton de la Fournaise is one of the world’s most active volcanoes. It is estimated to have erupted nearly 200 times over the last four centuries.
Flora
The frequency of eruptions and the abundance of flows constantly renew the configuration of Piton de la Fournaise and its slopes, keeping the landscape predominantly mineral. However, once the lava has cooled completely, plant colonization processes can begin. Lichens are generally the first to establish themselves, then other plant species grow in the crevices of the fertile soils: ferns, shrubs and, gradually, the forest takes over within a few decades.
Advice before entering the Fouqué enclosure
Leave early. Follow the signs and don’t lose sight of them, as the fog may surprise you.
Bring plenty of water, sun cream, a hat, good footwear, warm, waterproof clothing, a survival blanket, a flashlight and a first-aid kit.
IN CASE OF EMERGENCY: contact the Peloton de Gendarmerie de Haute Montagne (PGHM: 0262 930 930). Please note that not all volcanoes have good reception.
Here are a few ideas for hikes in the Fouqué enclosure, starting from Pas de Bellecombe.
Dolomieu crater (2632 m)
Duration: 5h30 round trip. Difficulty: difficult. Elevation gain: 510 m.
Kapor crater
Duration: 2h30 round trip. Difficulty: easy. Elevation gain: 200 m.
Rivals crater
Duration: 4h30 round trip. Difficulty: medium. Elevation gain: 300 m.
