Activity Bulletin of Saturday, October 17, 2015 08:00 (Local Time)
The eruption that began on August 24, 2015 at 18:50 continues.
Geophysical and geochemical indicators continue to show developments that are very clear since October 12. Since September 24, 2015, the intensity of the eruptive tremor moves up. On deformations side, the trend of deflation observed since September 27 has been confirmed in the following days but it is even clearer since October 11.
Concerning the geochemical indicators and particularly the gas flow, Figure 3 shows the evolution of the flow of SO2 from the last eruption. Looking more specifically the blue dots (daily average), there is a clear upward trend since the beginning of October. The CO2 measurements in the soil are also remarkable in terms of increase particularly in the gite of Pas de Bellecombe where measurements are performed several times a week.
The results of measurements and gas analysis conducted on the site eruptive on October 16, show that the emitted gases have a signature « low pressure » without remarkable change since the beginning of the eruption. Analyses of samples of lava sent in France are not yet known at this time. The increase of CO2 streams in Gite and the increased CO2 ratio / H2O in fumaroles summital seems to confirm an evolution in depth. For now, we have no evidence that a new magma happened to the surface.
In summary, geophysical and geochemical indicators show abrupt changes around October 12:
– Tremor: strong increase
– Gas: strong increase
– Deformation: strong deflation
On the eruptive site:
The site and activity have changed in recent days. Cone still grows. Its footprint exceeds 100 m in diameter and its height is estimated at 40 m. The increased flow of SO2 released to the vent creates very large bubbles which « splash« the external walls by large « packets » of lava. Compared with observations on October 12th, the bubble size, the size of « shreds« projected and the distance reached by the projections are without common measures. The whole is much greater including frequent outbursts.
Under pressure from the lava lake and under the effect of jolts, flanks of the cone slide under their own weight. We observed the marks of these mechanisms on the East and North sides and observed the occurrence of this phenomenon in the West. This is done by three times. 1 / destabilization of the flanck and appearance of fractures l; 2 / gravity sliding of the panel (visible to the naked eye – in minutes); 3 / An indentation is being created in top part, lava accumulations of lake will drain partially in the form of flows whose implementation is very fast.
Regarding the lava field, apart from the lava lake overflows, or even outside the periods during which the cone opens, there are no visible flow directly at the foot of the cone. The lava flows escape from the vent In tunnels and put in place from hormitos formed on the tunnel system. We observed at less than 100 m from the vent, but they are generally more downstream allowing the observation of flows from the Piton de Bert.
17/10/2015. Piton de la Fournaise, La Réunion :
Source : OVPF
Photos : Fournaise info