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Earth of fire

Actualité volcanique, Articles de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #Actualités volcaniques
 Shinmoedake - the eruption plume of 11.10.2017 - Doc.Nasa worldview EOSDIS

Shinmoedake - the eruption plume of 11.10.2017 - Doc.Nasa worldview EOSDIS

The JMA has raised the alert level of Kirishimayama / Shinmoedake to 3 / do not approach the volcano on March 1 at 16:40 local.

The seismicity is characterized by volcanic earthquakes and volcanic tremor since February 24 :

- 24.02: 23 volcanic earthquakes

- 25.02: 103 earthquakes volc.

- 26.02: 22 earthquakes volc.

- 27.02: 9 earthquakes volc.

- 28.02: 65 earthquakes volc. & 2 episodes of tremor

- 01.03: 40 earthquakes volc. & 2 episodes of tremor whose amplitude increases, until 10 am local.

Bad weather prevents observation of possible fumaroles.

GNSS observations show that magma accumulation has been going on for some months.

Source: JMA

Piton de La Fournaise - Histogram representing the number of superficial volcano-tectonic earthquakes recorded under the summit craters between January 1 and February 28, 2018. (© OVPF / IPGP)

Piton de La Fournaise - Histogram representing the number of superficial volcano-tectonic earthquakes recorded under the summit craters between January 1 and February 28, 2018. (© OVPF / IPGP)

Volcano-tectonic activity under the Piton de la Fournaise massif increased slightly during the last two weeks of February, with 63 events recorded between February 16th and 28th.

In February 2018, the OVPF recorded in total:

• 68 superficial volcano-tectonic earthquakes (0 to 2 km deep) beneath the summit craters;
• 3 deep earthquakes (> 2 km deep);
• 168 collapses (in Crater Dolomieu, at the Enclos Fouqué ramparts and at the eruptive site of July / August 2017.

Piton de La Fournaise - Illustration of the deformation since the end of the eruption from July 14-August 28, 2017 (the eruption of July 14-August 28, 2017 is here represented in yellow). Here is shown a baseline (distance between two GPS receivers) crossing the Dolomieu crater from north to south (in black the raw data, in blue the data smoothed over a week). A rise is synonymous with elongation and therefore swelling of the volcano; conversely, a decrease is synonymous with contraction and therefore deflation of the volcano. (© OVPF / IPGP)

Piton de La Fournaise - Illustration of the deformation since the end of the eruption from July 14-August 28, 2017 (the eruption of July 14-August 28, 2017 is here represented in yellow). Here is shown a baseline (distance between two GPS receivers) crossing the Dolomieu crater from north to south (in black the raw data, in blue the data smoothed over a week). A rise is synonymous with elongation and therefore swelling of the volcano; conversely, a decrease is synonymous with contraction and therefore deflation of the volcano. (© OVPF / IPGP)

Following the significant inflation in January related to intense hydrothermal activity, a consequence of the heavy rains of the beginning of the year, relaxation and deflation of the summit area was observed until about February 10th. Inflation (swelling) of the building has since been recorded again

The increase in seismicity during the last two weeks of February and the resumption of inflation in the summit zone were accompanied by variations in the CO2 concentrations recorded in the soil:
- Distal sector, region Plaine des Cafres / Plains of Palmistes: Downward trend.
- Sector near the Volcano Lodge: Strong increase

Piton de La Fournaise - Illustration of the summit deformation over 2 months. Here is shown a baseline (variation of distance between two GPS receivers) crossing the crater Dolomieu. A rise is synonymous with elongation and therefore swelling of the volcano; conversely, a decrease is synonymous with contraction and therefore deflation of the volcano. Any periods colored in light pink correspond to eruptions.

Piton de La Fournaise - Illustration of the summit deformation over 2 months. Here is shown a baseline (variation of distance between two GPS receivers) crossing the crater Dolomieu. A rise is synonymous with elongation and therefore swelling of the volcano; conversely, a decrease is synonymous with contraction and therefore deflation of the volcano. Any periods colored in light pink correspond to eruptions.

The decrease in CO2 concentrations in the far-field soil associated with an increase in fields near the terminal cone may indicate a transfer of the distant zones to the central zone (in line with the increase in peak inflation at the end of February).

It should be noted that the SO2 fluxes in the air recorded at the edge of the Enclos Fouqué are below or close to the detection threshold (the absence of detection is compatible with a magmatic transfer which remains always deep, below the level of the sea).

At the top, low concentrations of H2S (near the limit of detection) and sometimes of SO2 are always recorded.

Review of Piton de la Fournaise activity:

All these observations show for the month of February the continuation of:
- a deep re-feeding of magma (below sea level);
- a pressurization of the superficial magmatic reservoir which tends to accelerate.

Source: OVPF 01.03.2018
 

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