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Kaf (Novembre 2002)
June-July 2003 |
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| To understand the activity of the Piton de la Fournaise this winter 2003, let's go back 6 months earlier. On December 1st 2002, the eruption of Pit guanyin is ending when a sudden huge sismicity occurs, 400 meters of depth inthe SSW of the Dolomieu crater. The following days, about 1000 seisms per day are recorded so 1 seism per minute. On December 20th 2002 thousands of them per day are recorded, and some of them of 2.5 of magnitud. The authorities, concerned by a possible explosion, decided to close not only the enclosure, but also to forbid the access to the Plaine des Sables. |
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| The crisis finally ended the morning of December 23rd 2002 after an important earthquake. We discovered later a field of fumaroles in a 1 hectare collapsed area. This zone situated in the SSW of the crater Dolomieu, against the West part of the crater of the eruption of december 29th 1985. There were no phreatic explosion as the vapor and the gas managed to escape calmly from the earth. Now this aera is fragilized and we were expecting the next eruptions in this area. In March 2003 the seismic activity revived and no deflation in the main crater zone, anouncing the sson awake of the volcano. A seism with a magnitud lightly over 2 has been recorded on May 29th. Without more signs, a first eruptive phase , preceded by 17 minutes of seisms, began as anticipated in the collapsed area on may 30th, from 11:55am to 2:15pm, pouring less than 300 000 m3 of magma. The following days, a momentary resumption of the tremor indicated that a second phase was coming. This phase also began without signs on June 4th at noon and ended on June 6th in the evening with a plume of ashes in the forming crater. On june 10th and 11th, new seisms indicated a3rd phase was coming ... June 12th was calm and on the 13th, around 3:00am the eruption slowly recovered in exactly the same forming cone now called ... KAF. This 3rd phase similar to the preceding phase ended during the night of June 14th/15th and produced less than a million m3 of magma as in phase 2. On June 16th, these 3 phases covered about the half West of the Dolomieu crater. On June 18th, there was a low sismicity and in the early morning of june 22nd, the phase 4 began slowly. A bad weather due to the very active winds called Alizes impede us to see the site of the eruption and its exact location, but it seemed to be in the fragilized previous area. During the night of June 22/23, the first observants noticed fountains of lava springing from an aperture situated by the Kaf. A pahoehoe flow, not very active, was emerging from a tunnel situated at the base of the crater Kaf. The eruption progressively went out during the week-end of July 5th and 6th after 2 weeks of activity. Can we expect phases 5 and 6, even 7, of the same kind ? Each of them separated only by a short periods of inactivity ? It is impossible of course to tell, but the absence of deflation in the summit zone and the low quantity of magma emitted during these phases (less than 3 millions m3) give us a lot of expectations and the eruption might not be over ... Also, these events reveal that the collapsed area is very fractured, the activity of the volcano shows that there is an aperture on the superficial reservoir of magma ... The eruptions begin without many precursory signs and last a short time, just a soft pressure of gas would be enough for the magma to go out. Considering this situation, the Piton de la Fournaise is in a new situation and make it difficult to know when that kind of short but numerous activities will stop. |
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| Cliquez sur les zooms pour afficher les photos. Elles s'ouvriront dans une nouvelle fenêtre que vous pourrez fermer en cliquant sur la petite croix en haut à droite. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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