October 17, 2015. EN. Piton de la Fournaise, Copahue .

Home / blog georges Vitton / October 17, 2015. EN. Piton de la Fournaise, Copahue .

October 17, 2015. EN. Piton de la Fournaise, Copahue .

17/10/2015.

 

Piton de la Fournaise, La Réunion :

 

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. The figure 1 clearly shows that, since October 12 the slope is very strong with a jump on 14th.

rsam_rvl.hhz_.pf_.00_20151017_0000

(©OVPF/IPGP)

Figure 1: RSAM (seismic intensity) recorded by the Station Rivals since the beginning of the eruption.

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.

lignes_de_base_20151016

©OVPF/IPGP)
Figure 2: Examples of changes in deformation on three base lines (distance from station to station) – A: at the top; B: at the base of the summit cone and C: over long distances
so2_24-08_au_13-10

(©OVPF/IPGP)

Figure 3: SO2 Flux from August 24 to October 13, measured using the NOVAC station of Piton Bert.

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.
About the flux of lava, Figure 4 also shows a sharp inflection of the curve since October 12, resulting in a significant increase.

debit_20151016

(©OVPF/IPGP)

Figure 4: Change in average flow (average Time Discharge Rate) since August 24.

In summary, geophysical and geochemical indicators show abrupt changes around October 12:
Tremor: strong increase
– Gas: strong increase
Deformation: strong deflation

piton

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.

piton

©OVPF/IPGP)

Figure 5: Figure of the opening of the cone on its west side (Photo OVPF).

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 partlava accumulations of lake will drain partially in the form of flows whose implementation is very fast.

piton

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.

Source : OVPF

Photos : OVPF, Fournaise info , Johan Photography.

 

 

Copahue, Chili :

The level of activity of the volcano is at YELLOW level: changes in the behavior the volcanic activity.


Based on the analysis of information collected by the monitoring equipment and surveillance of the volcano, the National Geology and Mining Service (SERNAGEOMIN) through the Volcano Observatory of the southern Andes (OVDAS), announces:

 

copahue– During this period, three hundred and thirty (133) earthquakes were recorded.

Seventy-two (72) correspond to events volcano tectonic (VT associated with rock fracturing). Similarly, eleven (11) events long period (LP) and fifty (50) long period earthquakes (VLP) were classified.
Regarding VT seismicity, local magnitudes (ML) were less than or equal of M3.6   and epicentral locations show a wide distribution, although most are concentrated on the northeast flank (NE) at distances less than 10 km from the crater EL Agrio, and at depths of less than 9 km.


Regarding the LP type of events, they had local magnitude (ML) of M 1.2   and the maximum values of reduced displacement (DR) of 0.5 cm2.
The type of recorded seismicity VLP showed equal and lower local values of M0,7 and reduced values of displacement (DR) to the maximum of 14 cm2, mostly located around the crater with epicentral distances of less than 4, 5 km.

 


The tremor remained at values of DR oscillating, usually below 0,7cm2, averaging 0,4cm2, considered low for this volcano, focused on the dominant frequencies between 1.0 to 4.5 Hz.

 


On the surface activity when weather conditions have allowed, IP cameras installed near the volcano showed the presence of incandescent at night and a continuous emission of gas and ash from the active crater. These emissions are characterized by a grayish color, which show the presence of particulate matter (ash), a process that has been observed since October 6 (REAV October 6, 2015 1:00 p.m. HL).

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Finally the emission column reached a height of 1000m above the crater.
On 11 October, a survey was conducted to check the condition of the acid lake of the crater El Agrio.
In the area, it was possible to note the disappearance of the acid lake and instead, there was a deposit of material due to ash fall.
. In addition, the thermal images have a maximum temperature of 500 ° C from the center of emission.

Therefore, it is reiterated:
The recommendation of an exclusion zone of 2.5 km around the crater El Agrio considered as high risk area and the level of technical warning remains yellow.

Source : SERNAGEOMIN -OVDAS

Photo : J.Ovalle

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