The amount of magma emitted during the eruption of Piton La Paix (over on August 14th after 26 days of activity) was clearly lower than the amount responsable for the swelling in July before the ruption. This lead the director of the Volcanologic Observatory, Thomas Staudacher, to prepare for another eruption during the following months.
The awakening of La Fournaise occured with very few signs on August 30th and surprised everyone. Two breaks opened around 11:35am, the first one was very active located southeast of the Dolomieu crater, close to the Rampart and the second not very strong, on the edge of the summit cone, stopped a few hours later, giving birth to a small lava flow barely reaching the crater Maillard.
I arrived on site with Alain Gerente around 4:00pm the same day, a lava flow was covering the northeast quart of the Dolomieu, pouring out of a forming cone half collapsed, 3 to 4 meters high and emitting up to 50 meters high fountains of lava. 20 meters away a lava lake surrounding part of the break will last until midnight. This lake was fed by a fountain and arisen by bubbles of gas over 1 meter round.
In the evening of September 1st, the half collapsed crater, up to 10 meters high, closes. the magma travelled through tunnels and numerous resurgences appeared between the cone and the rampart at the foot of La Soufrière.
Starting september 3rd, the bad weather installs over La Fournaise for a week and on September 10th when it clears off, the forming crater was now over 20 meters high and projectiles of magma had covered entirely the area between the cone and the rampart.
September 12th, the small lava lake that had stopped on August 30th awoke and a fountain of lava appeared. Later the level of the lake arose, reaching the rampart's and flooding over its edge, giving birth to a new flow of "shelly pahoehoe" running down towards the crater Maillard. 2 days later the lake collapsed as the lava flowed inside the Dolomieu.
For the first time since 1930, it is now possible to walk into the Dolomieu without climbing down.
Since september 15th, thick lava flows of pahoehoe slowly covered most of the surface of the main crater. Inside the new crater called La Wouandzani (fraternity in comorian), an agitated lake of lava persisted emitting occasionnally projectiles of lava falling over the edge.
Begining of October, the dolomieu was filled up about 75% of its depth by the new flows, considerably changing its appearance.
Sunday 8th of october, the weather center of Reunion Island announced the arrival of a cold front from the antartic, forecasting snow showers and strong wind over La Fournaise the same night.The night of the 9th, a few inches of snow covered the crater like in august 2003, it is very rare weather at 2000 meters of altitud only, under the tropics !
We had to wait the day after in the afternoon, when the weather cleared up , to hear from the erupion. The firsts on site were amazed to discover a new forming cone about a hundred meters from La Wouandzani.
Pahoehoe lava was pouring out of it covering the floor of the Dolomieu crater. It was named first Piton La Neige by reporters without the approval of the Volcanologic Observatory that decided to name it Piton Moinama (the brother in comorian).
In the afternoon of October 11th, we flew over the crater La Wouandzani in helicopter and saw a small lavalake still very active. The following days its activity stopped and the crater collapsed losing a third of its height.
The day after, the Moinama was closed.
During the last 3 weeks of October, this new forming cone went through different stages of construction and destruction to finally reach 30 meters high on October 31st. The pahoehoe flows now filled up 95% of the Dolomieu.
The first 3 weeks of November, the lava flows went on spreading around the Dolomieu and reached its edge on the east side. At the end of the month, a channel of lava built in this area pouring the lava out of the Dolomieu towards the crater jean at 1500 meters of altitud.
In early December, the "head" of the flows reached the "Big Slopes", 1200 meters high. Mid-December it was located only 5 km away from the coast. The 20th, the channel was not supplied with lava anymore due to a new resurgence that opened between the Moinama and La Wouandzani, and built a third cone, 15 meters high, in 48 hours. A 4th cone appeared on the 23rd between the Moinama and the 3rd cone.
On December 27th when the weather permitted, we could observe the 3 erupting cones (Moinama, 3rd and 4th cones) each containing a lake of lava. The 3rd cone's lake was overflowing under the gas pressure covering entirely the edges with spectacular waves for a few minutes, 3 to 4 times per hour.
The following days, the activity slows down and the eruption ceased at 12:57am on New Years day.
During these 4 months of eruption the Dolomieu crater grew 20 to 30 meters higher and over 15 millions cubic meters of lava spreaded around the summit and its East flank.