The island of La Réunion lies in the Indian Ocean above a so-called hot spot, a particularly hot spot in the earth's mantle where basalt melt rises into the earth's crust. The oceanic plate drifts over such a stationary hot spot and leaves a chain of volcanoes on the earth's surface. On La Réunion, the extinct Piton des Neiges and the active shield volcano Piton de la Fournaise (= "glowing furnace") are the visible members of this volcanic chain.
The caldera Enclose FouquéThe "furnace" is a quite young volcano, whose formation began approx. 360,000 years ago. At its base it has a diameter of 50 kilometres, and at its summit two calderas nested into each other were formed. The outer caldera is called Rempart. In it lies the Enclos Fouqué. This inner collapse crater measures 13 x 8 kilometres and is open to the sea, in the shape of a horseshoe. The slope open to the ocean surrounds an area called Grand Brulé, which is often the scene of large fissure eruptions, for which the Piton de la Fournaise is famous. Through this area the lava flows flow down towards the sea. In the "Enclos Fouqué" there is also the summit cone with the two craters Dolomieu and Bory. On this map you can see the Caldera very well.
Volcanic eruptions at FournaiseThe Piton de la Fournaise is one of the most active volcanoes in the world. It has erupted more than 160 times since the 17th century. Normally its eruptions within the caldera are quite harmless, but occasionally fissures open on the volcanic slope outside the caldera rims: then lava flows can enter inhabited areas and threaten villages. In 1977, such a lava flow destroyed houses in the village Sainte-Rose and partially encircled the church there, but without destroying it.
The eruption of 1998In 1998, Piton de la Fournaise entered an extremely active phase. Before that the volcano rested for 6 years and gathered strength. At the beginning of 1998 the signs of an imminent eruption increased. The mountain swelled like a Yeast dumpling, because magma was rising. At the same time the frequency of earthquakes increased. On Saturday, March 7, the first warnings were issued. On Sunday 8 March a seismic crisis began. Over 1000 earthquakes per hour were registered. The volcanologists finally raised the alert. The eruption was imminent. On Monday at 15.05 the tremor, a constant quake and trembling of the earth, began. The magma was on its way! On the flank of the volcano, the ground cracked open, creating a system of crevasses from the summit of Fournaise to a secondary crater. Over a length of 1 kilometer, 50 meter high lava fountains shot into the air. After one hour most of the fissure system closed again. The following day volcanic activity was concentrated on two eruption centers. A lava flow was flowing towards the sea, but without reaching it. On 11. March another fissure opened on the northwestern flank, which produced only little lava. From the end of March only the Kapor crater was active. The crater Katja and Maurice Krafft (named after the volcanologist couple who died at the volcano Unzen in 1991) and the small crater in the northwest, were just steaming along.
This eruption was the prelude to a whole series of eruptions in the Enclose Fouqué. Since then the volcano has erupted 2-3 times a year.
Spectacular was an eruption in September 2004, when the lava flows reached the ocean within a few days. A battle of the elements erupted and huge clouds of steam rose into the sky.
The fissure eruption in 2007In April 2007, a 1 km long fissure opened in the Grand Brulé, the lower end of which was at an altitude of only 590 meters above sea level. Within one day the lava flowed into the sea. Several cones formed on the fissure from which lava fountains shot into the sky. The lava flows flowed along the edge of the caldera and especially the gases threatened the foothills of Tremblet. The clouds of steam rising from the ocean released sulphuric acid rain over the mountain forests and defoliated the trees. This eruption was one of the strongest eruptions of the last 100 years! The crack formed in the lower part of the magma chamber, whereupon a very hot residual melt with large olivine crystals leaked out. This tholeitic basalt lava is called oceanite. The falling magma level caused a series of landslides and subsidence in the summit area, resulting in the two summit craters merging. The bottom of the summit crater sank by 100 m. A total of 130,000,000 cubic meters of lava were produced.
The recent eruptions at Piton FournaiseSince the 2007 eruption, the Piton Fournaise has become quiet! The volcano remained dormant until November 6th 2009, when a small eruption began which lasted only briefly. In the following years only a few small eruptions occurred at the summit crater and short-lived fissure eruptions limited to the caldera. Since 2014 the frequency of these eruptions has been increasing: they occur on average 3-4 times a year and last about 14 days. There have also been some seismic crises that were not followed by an eruption. The last eruption so far began on September 15, 2018.
Online since 2001. Last updated 2018.