Volcanological BULLETIN FOR THE MONTH OF July 2015
Following the eruption of May 2015, except the deformations (see later in the text), the volcano has shown that very few signs of activity throughout June (less of an earthquake under the summit per day and moderate to low flow gas). Since the beginning of July the sensors of OVPF recorded a marked increase in activity. This situation led the prefecture to spend at alert level “imminent eruption” on July 6. The alert level was dropped later but the prefecture has maintained an order prohibiting access to the summit because of the risk of occurrence of an eruption and / or landslides.
431 volcano-tectonic earthquakes summital (VTS) and 581 collapses of rocks in the crater Dolomieu were recorded between the 1st and 29 July representing more than 15 VTS by days with significant variations:
– 92 (VTS) on July 6 – 47 (VTS) on July 13 – 47 (VTS) on July 26 – 67 (VTS) on July 27 – 50 (VTS) on July 28
Seismic activity between the 1st and 30 July 2015 (© OVPF / IPGP)DeformationDuring the month of July, the deformations of the terminal cone have continued with a significant acceleration (2mm / day on top) between the 1st and 19 July, at which time the seismicity has resumed.
The beginning of a new acceleration seems to be emerging since July 26.
Cumulatively, the shifts observed since late May show a cone inflation of about 3-4 cm.
This reflects the continuation of a pressurization in depth. The distribution of deformation and the models show a pressure source located around 1-2 km deep under the Dolomieu crater.
Total emitted of volcanic gases
* Fixed DOAS (NOVAC – Bord de l’Enclos)Flux of SO2 below or near the detection limit (= diffuse emissions, no gas plume supported)
* Multigas (DSO – Piton de la Fournaise top):
The high concentrations of H2S that preceded the seismicity peaks of 06 and 13 July are not detected. Since July 10 is detected fairly low concentrations of H2S and a slight increase in SO2 emissions.
The increase in micro-seismicity observed since July 21 was preceded and associated with an increase in water vapor emissions and CO2 enrichment of gaseous emissions.
* CO2 Flux floor (Rift Zone NO): – BLEN (Piton Blue) Stable to high values – PNRN (Plaine des Palmistes): Stable to high values – PCRN (OVPF): Stable to high values
Evolution of ratio CO2 / SO2 since the end of the eruption of May 2015 (© OVPF / IPGP)
The volcano finally erupted this morning around 9:35 in the northeast of Enclos, at the Piton Fugasse, not far from the famous Piton Kapor, between the top and the Nez Coupe Sainte-Rose, about 1 900 meters above sea level. Lava fountains are visible and aerial reconnaissance currently applicable.
July 31, 2015. Piton de la Fournaise, La Réunion :
Source : OVFP.
Photo : aupieddenosvolcans