Paul-Edouard de Lajartre - Eruption La Fournaise aprill 2007

Only a week after the eruption of Pitons La Wouandzani et Moinama, a new sismic activity and a swollen summit indicate a forecoming eruption. On February 18 before 5:00pm La Fournaise awakes. A new opening erupts through the Dolomieu East towards West exiting on the East flank of the Dolomieu. But the eruption stopped a little after midnight.

For the volcanologic Observatory, this short eruption is jsut a prelude to a much bigger one. The seisms started again end of February and increased the following weeks to reach a hundred of seisms per day end of March. Most of all, a significant swelling of the summit was recorded by the different stations of the Observatory.

The awakening of the volcano started at 11pm on March 30 close to the Formica Leo in the southeast area of La Fournaise. This eruption also stopped soon, around 8am the day after, but the seismic activity moved towards the eastsoutheast area and reached the impressive rythm of 1 seism per minute on April 1st !

The new eruption was planned to open in the lower part of the Enclosure. It started around 10am on April 2nd with a break opening at 600/700 meters of altitude colse to the Rempart du Tremblet.

Considering how close it is from the ocean, the lava flows reached the sea in less than 10 hours. The day after the sismic activity increased a lot under the Dolomieu (1000 seisms per day) so the Volcanologic Observatory announed the possible collapse of the Dolomieu.

April 4th, seisms of magnitud 3 were noticed at the gîte du volcan (The Volcano lodge) while a deflation of the Dolomieu was recorded by the stations. The summit area became very dangerous and l’Enclos (the Enclosure) was closed even to professionals.

At the same time, the flux of lava reached an exceptional level, a record for Reunion Island, with over 100 cubicmeter per second (8 to 10 million cubic meter per day). The front of the lava flows joining the ocean was over 1 kilometer wide and created a 3000 meters high plume of steam and hydrochloric acid !

Due to the fragmentation of the lava in contact with water, Pele's hairs and particules of lava were carried away by the plume all over the island. The Flora in Grand Brûlé and the Tremblet area were partially burnt by this phenomena as well as acid rains.

The Dolomieu began to collapse on April 6 in the morning but the wetaher was bad and no observation was possible. On the 7th, in the morning, the weather got better allowing us to fly over the Dolomieu by helicopter.

The platform of the Dolomieu was replaced by an abyss 350 meters deep and the volume of the collapse was estimated at 120 millions of cubic meters.

The last collapse of the Dolomieu happened in 1930-1931 but was less important.

This gorgeous crater with beautiful twisted pahoehoe lavas became a huge inesthetic gulf very instable and dangerous.

These collapses went on the following days along with ash plumes. This will be at the expense of La Soufrière . A huge break also opened in the crater Bory and a part of this crater might disappear in the near future.

The activity by the ocean decreased on April 7th even though in the morning of that day 2 gigantic fountains of lava could still be seen 10 kilometers away. The erutpion ceased during 10 hours but the 2 fountains reappeared again the day after although smaller along with many lava flows. In the morning of April 13, a phreatomagmatic eruption ended one of the fountains' activity while the second one disappeared 2 days later.

On April 16 a huge degas occurred in the crater.

The following days, a long channel of lava appeared at the foot of the crater. Its path was sprinkled with small hornitos built after an sudden raise of pressure in the tunnel. The lava was resurfacing at 300/400 meters of altitude occasionnally reaching the ocean.

The eruption ceased on the 30th but some lava was still flowing from the emptying tunnel the following days.

The Volcanologic Observatory estimated 120 millions cubic meters of lava emitted during this eruption which represents the highest amount known in the history of La Fournaise. A third of it went into the ocean building a platform of 35 hectareas and 4 kilometers square covered forests and gullies.

Since the end of April the Observatory is still recording seisms 1 to 7 kilometers under the ocean's level on a daily basis, possible signs of a refill of the superficial magmatic chamber located right under the Dolomieu. Also, numerous collapses persist inside the Dolomieu and the future reopening of this area is problematic.