Piton de la Fournaise, La Réunion : The morphology of the lava lake has evolved again.

Piton de la Fournaise, La Réunion : The morphology of the lava lake has evolved again.

The current eruption continues.
On the morning of Sunday, October 11 (7:45 in the forty ninth day of eruption) eruption which began on 24 August is still ongoing. At 7:45 this morning the sky is (like yesterday) completely clear from the coast to the summit of Piton de la Fournaise.
The level of activity remains high and comparable to that in previous days. However a slight tendency to decrease in activity was recorded in the last days (see detailed report of October 9 below).
Geophysical and geochemical indicators showed since 1 October (date of the last bulletin) some evolutions.
Since September 24, 2015, the seismicity moves up. Note down slightly early in the day (we will look if it is confirmed that WE). The increasing trend is not as significant on Bory and Dolomieu South or even on other network stations.

The trend of low deflation observed since September 27 was confirmed both in summit area, at the base and at a greater distance. This trend is still quite sensitive. Here we measure the variation of distance (called baseline) between summital GNSS stations, stations at the base of the central cone and stations at a greater distance (sometimes outside of l’Enclos). Deflation measured on the last 10 days is lower than 5 mm.

The gas flow measurements were possible with the return of warm weather (the weather limiting optical measurements).
After a period during which we recorded significant flows of CO2 in soil values have decreased significantly since October 4th.
Flows of SO2 remain constant in the plume and at the top.
We note a significant increase in water vapor at the top of the volcano.

The flow measurements are made mainly at a time from the luminescence of Modis and MSG satellite images, and at the same time by applying a law of correlation between the flow of and the lava flow. Of course, the bad weather had significantly reduced these measures for two weeks. Since the return of good weather we observed a peak of lava flow equal to 11m3s– 1–on October 4 and then return in the range of 5 and 10 m3s-1 as before.

In summary, geophysical and geochemical indicators remain at a high level with a slight downward trend for those who are related to a pressurization of the volcano. The hypothesis formulated following this at a month and half of eruption is that deep fluids (gas and magma) arrive in the upper part of the volcano and at the surface (at least for the gas certainty) as puffs (as cycles in the gas flow and in the strains).

On the eruptive site:

Benefiting from the return of fine weather we could observe the eruption from the eruption Site every day of the week from Tuesday, October 6.
The cone is still imposing. Our estimates of height (about 30-35 meters) have been confirmed by measurements made by topography (daily 06.10.2015).

The morphology of the lava lake has evolved again. While in previous observations, a perfectly circular lake upstream and downstream a small mouth were visible, both wells are one with a general geometry of a calbasse.

Wednesday, October 7th in the evening the cone is partially breaking, creating a breach 5 to 7 meters high in its upper part. A flow of lava escaped from it.
The gas reaches the surface of the lake in the form of large bubbles which propel lava packets above and on the edges of the cone. It is these bubbles which release the gas of plume always rich in SO2 but less rich in water vapor (white plume least).

The flows are mainly composed of smooth lava (pahoehoe) issued by ephemeral vents present on the area of lava field cooled at the surface (tunnels). What is notable is that a very large part of the field is covered by these type of pahoehoe flows, from the foot of the vent until more than two and a half kilometers downstream , burning vegetation at the foot of Piton Bert. Furthermore, at the location of many ephemeral mouths the accumulation of lava constituted some morphology of hornitos.

October 11, 2015. Piton de la Fournaise, La Réunion :

Source : OVPF

Photos : Arnaud Barrey .

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