Piton de la Fournaise: what type of volcano?

Piton de la Fournaise is one of the most active volcanoes in the world. Located on the island of Réunion, this volcano, which rises to an altitude of 2,632 metres, is fascinating not only for its frequent eruptions but also for its unique geology. In this article, we explore the type of volcano that is Piton de la Fournaiseand how it works.

A Hawaiian-type effusive volcano

Piton de la Fournaise is a classic example of the shield volcano. This term describes a broad, low-lying form with gentle slopes, created mainly by basic, fluid lava flows that spread over vast distances. The term "shield volcano" refers to the shape of the volcanolike a shield on the ground.

The special feature of these volcanoes is their structure. Unlike explosive volcanoes such as Vesuvius in Italy or Mount St Helens in the United States, Piton de la Fournaise is an effusive volcano because it does not tend to accumulate large quantities of gas under pressure. This leads to effusive rather than explosive eruptions, typically associated with Hawaiian volcanoes.

Origin and formation of Piton de la Fournaise

The Piton de la Fournaise is in fact the summit and eastern flank of the Piton de la Fournaise massiflocated in the south-east of Reunion Island. Along with the Piton des Neiges, these two volcanoes are at the heart of the island.The origins of the island of Réunion (with a third volcanothe trade winds volcano, about which little is known today).

The origins of Piton de la Fournaise are to be found in a hot spot under the island of Réunion. A deep mantle plume brings in hot magma on a constant basis, feeding the volcano. This continuous source of heat partly explains the frequent eruptions observed.

Formed around 500,000 years agoThe Piton de la Fournaise volcano has gradually built up its successive layers of lava. Fluid lava emanating from fissures and craters has gently shaped its current profile, in contrast to the steeper structures found in other types of volcano.

Eruptions and volcanic activity

One of the world's most active volcanoes

Generally harmless eruptions, but not always...

Although spectacular, the eruptions of Piton de la Fournaise are generally harmless to the island's inhabitants. The lava flows are advancing slowly and are mostly confined to the Enclos Fouqué, a vast caldera formed by an ancient collapse.

Occasionally, lava flows from Piton de la Fournaise descend all the way down the Grandes pentes and the Grand Brûlé, the lower parts of the Enclos, to flow into the Indian Oceanas for the 2007 pouringfor example.

Some lava flows have also come out of the Enclos area, affecting villages and threatening local residents, such as those of 1977 in Sainte-Rose, 1986 at the bottom of St Philippe and 1998 in the upper reaches of Ste Rose.

L'The eruption of 1977 is still remembered by the people of Réunionand its intensity. Fortunately, the residents of Sainte-Rose were evacuated before the lava flow arrived, destroying 33 homes, the police station, the main road and 290 hectares of farmland. The church, now renamed Notre dame des Laves, was miraculously preserved, as the lava stopped at its door.

The formation of the Dolomieu and Bory craters

Piton de la Fournaise currently comprises several cratersincluding one of the largest craters in the world:

• Le Dolomieu craterthe largest and located to the east

It is 1,000 metres long (1km) and 700 metres wide. It is thought to have appeared in 1791, following the collapse of a magma chamber at the summit. It was named by Bory, a naturalist and geographer, as a tribute to a geologist and mineralogist of the same name, Déodat Gratet de Dolomieu. The crater's current dimensions are due to the eruption of April 2007, which caused it to collapse and dramatically altered its morphology.

Another crater was well known:

• Le Bory craterto the west

This crater was smaller: 350 m long and 200 m wide. Already present when the island was first colonised, it was named after the expedition led by Jean-Baptiste Bory de Saint-Vincent in 1801. Since the collapse of the Dolomieu crater in 2007, this crater no longer exists, as the two craters now form a single crater.

Observation of its activity

Piton de la Fournaise is a major an extraordinarily useful natural laboratory for vulcanologists. Studying its eruption cycles not only helps to understand the inner workings of volcanoes in general, but also to predict future eruptions not only locally but potentially in other parts of the world.

Since the Volcanological Observatory was set up in 1979, Piton de la Fournaise has been one of the most closely monitored volcanoes in the world. The observatory (Piton de la Fournaise Volcanological Observatory, IVPF) is part of theParis Institute of Globe Physics (IPGP), a geosciences research institute, responsible for observation services in volcanology, seismology, magnetism, gravimetry and erosion.

Thanks to continuous observation of the volcano, the observatory enables the authorities to predicting volcano eruptions and protect the people of Réunion Island.

Surveillance technologies

A arsenal of modern technologies is deployed for monitoring Piton de la Fournaise. The tools used include :

- Seismographs to detect earthquakes indicating magma movements.

- GPS to measure ground deformation, a sign of rising magma.

- Thermal cameras to monitor surface heat flows.

Impact of Piton de la Fournaise activity on Réunion's geology

Little by little, vegetation reclaims lava flows. The first plants to settle are lichens, whose decomposition eventually provides the humus needed for vegetation.

These whitish lichensIn some places, these give a light colour to the slopes of the volcano, as on the Grandes Pentes. Then other plant species grow in the crevices of the fertile soil: ferns, shrubs and, gradually, the forest takes over.

Admire the Piton de la Fournaise, its craters and pitons

The Piton de la Fournaise attracts thousands of visitors every year. A number of hiking trails provide access to secure observation points, offering a breathtaking view of the volcano. breathtaking view of the Dolomieu crater and other pitons formed during recent eruptions.

These trails start at the pas de Bellecombenear the Dolomieu crater. A 1-hour walk from this starting point takes you to the Dolomieu crater. Formica Leo provides a great view of the volcano. If you want to reach the Dolomieu crater, you'll need to walk for around 6 hours round trip.

Practical information for visitors

If you're planning a visit to Piton de la Fournaise, there are a few things you should know:

• Always ask about the current state of the volcano before your visit. The local authorities and the official website of the Observatoire Volcanologique du Piton de la Fournaise provide regular information and updates.
• Equip yourself properly. Sturdy footwear, plenty of water and good sun protection are essential for your excursions.
• Follow the safety instructions posted on site. Never venture off the marked trails without permission.

Although the term active volcano may seem intimidating, Piton de la Fournaise is actually much safer and better understood than most other active volcanoes high intensity.

Its effusive nature and frequent but predictable eruptions make it a must-see destination for volcano enthusiasts and research professionals alike. An in-depth understanding of this volcano provides a model for studying other basaltic volcanoes around the world, making a major contribution to modern geological science.