Réunion, a Hawaiian volcano

There are two main types of volcano: effusive and explosive.

Effusive volcanoes are characterised by relatively calm eruptions that produce fluid lava flows that flow down the sides of the volcano. Effusive eruptions can last a long time and can create shield volcanoes, which have gentle, broad slopes, such as Mauna Loa in Hawaii or Piton de la Fournaise on Reunion Island.

Explosive volcanoes, on the other hand, are characterised by violent, explosive eruptions that hurl ash, rocks, volcanic bombs and fiery clouds into the air. Explosive eruptions can produce columns of ash and gas that can reach altitudes of several kilometres into the atmosphere. Explosive volcanoes can have steep, conical shapes, such as Mount Saint Helens in the United States or Vesuvius in Italy.

The two families of volcanoes are fed by different sources of magma, with different chemical compositions and viscosities, and are associated with subduction zones, rifts, hot spots or other geological processes.

But why Hawaiian-style?

These two families include different types of volcano.

A Hawaiian-type volcano is a type of shield volcano that is typical of the Hawaiian Islands. This type of volcano is characterised by relatively calm effusive eruptions that produce large fluid lava flows and lava fountains.

Shield volcano?

It is so named because of the general shape of its volcanoes, which resemble a shield resting on the ground. It's hard for any hiker or runner on Reunion Island to admit that the terrain is fairly flat, but this is a tricky configuration as only 10 % of the massif emerges from the ocean. The massif is 220 km in diameter at the oceanic base, 4000 metres below sea level, and around 70 km in diameter at sea level.

The calderas and erosion have carved out rivers, gullies and canyons. The calderas and erosion that carved out the rivers, gullies and canyons have given this surface configuration a very pronounced verticality (thanks to our thighs...).

Passing 4000m + 3000m rounded off for the summit of the Piton des Neiges, Réunion measures 7000m, making it one of the highest volcanoes in the world as well as being one of the most active!

It is generally agreed that the hot spot feeding the Piton de la Fournaise is geologically linked to the Indian plate, which 65 million years ago was attached to the African plate above this same hot spot. The entire series of Laquedives, Maldives, Chagos and Mascareignes islands are thought to have formed as a result of movement above this point. The meeting with the Asian plate formed the Himalayan chain.

These volcanoes tend to have prolonged eruptive activity and their lava is often used to create new land by merging with the sea.