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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
 Piton de La Fournaise - crater Dolomieu - photo archives © Bernard Duyck

Piton de La Fournaise - crater Dolomieu - photo archives © Bernard Duyck

A new acceleration of seismicity observed this Sunday at Piton de La Fournaise shows that the pressurization of the reservoir is accelerating and that the latter is weakening.

Since April 21st, the seismic activity above the Piton de la Fournaise summit has resumed with 24 earthquakes registered on April 22nd. These superficial volcano-tectonic earthquakes (<2 km deep) were recorded below the summit zone.

Piton de La Fournaise - Histogram representing the number of superficial volcano-tectonic earthquakes recorded under the summit craters between April 4 (end of the last eruption) and April 22, 2018. (© OVPF / IPGP)

Piton de La Fournaise - Histogram representing the number of superficial volcano-tectonic earthquakes recorded under the summit craters between April 4 (end of the last eruption) and April 22, 2018. (© OVPF / IPGP)

This resumption of seismicity and the acceleration observed yesterday are the result of:
- the continued inflation (swelling) of the building observed following the end of the eruption of April 3-4 (up to 2.5 cm of elongation at the summit in 15 days), synonymous with a deep refeeding in magma and a pressurization of the superficial magmatic reservoir;

- a large increase in the CO2 concentration in the soil observed in the far field following the end of the eruption of April 3-4, followed, from April 19, by a very strong drop in concentrations. This geochemical evolution also highlights a continuation of the deep recharge and a possible transfer to lower depths (shallow reservoir) since mid-April (lower CO2 ground).

Source: OVPF - Activity Bulletin 23.04.018 / 12h loc.

Piton de La Fournaise - Illustration of the summit deformation over 2 months (24.02 - 24.04.2018) Here is shown a baseline (variation in 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 (24.02 - 24.04.2018) Here is shown a baseline (variation in 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 - Average concentration of CO2 in the soil at the Volcanological Observatory (Bourg Murat) between February 1 and April 23, 2018 (the eruption of April 3-4, 2018 is shown in red). The values ​​are normalized to the maximum value recorded. (© OVPF / IPGP)

Piton de La Fournaise - Average concentration of CO2 in the soil at the Volcanological Observatory (Bourg Murat) between February 1 and April 23, 2018 (the eruption of April 3-4, 2018 is shown in red). The values ​​are normalized to the maximum value recorded. (© OVPF / IPGP)

Observations made by the Department of Meteorology and Geological Hazards of Vanuatu / VMGD on 21 April 2018 during an overflight of Ambae confirm that the April eruptions modified the volcanic cone of Lake Voui.

The cone is now bigger and a big crater has formed. A small lake is present in the active crater. During the month of April, eruptions typically consisted of volcanic ash emissions and lava fountains. This created falling ash and slag on Ambae. The eruptions also produce volcanic gas, always perceived, and acid rain.

The lakes of Ambae Island: the Manorogoro, the Voui, and the Manoro - the active cone cuts Lake Voui in two parts - photo VGO / VMGD
The lakes of Ambae Island: the Manorogoro, the Voui, and the Manoro - the active cone cuts Lake Voui in two parts - photo VGO / VMGD

The lakes of Ambae Island: the Manorogoro, the Voui, and the Manoro - the active cone cuts Lake Voui in two parts - photo VGO / VMGD

The presence of ash on Ambae has changed the behavior of streams and creeks when it rains. Streams can produce flash floods and carry much more debris (sands, gravel and rocks). The path of streams and creeks may change due to flood debris. A landslide can occur in some areas during heavy rains.

These observations and the analysis of the seismic data confirm that the minor level of volcanic activity continues. The activity of the volcano consists of a continuous emission of steam and gas, with volcanic ash during explosions.

The alert level remains at 3, with a prohibited area of ​​3 km radius around the vents.

For the news, a small eruption occurred on April 23 at 4:06.

Source: VMGD

Kilauea - the widest lava overflow north of the crater Overlook 22.04.2018 - photo HVO-USGS

Kilauea - the widest lava overflow north of the crater Overlook 22.04.2018 - photo HVO-USGS

In Kilauea / Halama'uma'u - summit crater, after a first overflow of lava from the crater Overlook reported yesterday, the HVO observed four more on 22 and 23 April 2018, while the tiltmeter continued to record inflation.

The most important was the fourth, which started on 23.04 at 6:30 am and continued for three hours; lava covered about a third of the Halama'uma'u crater, drowning much of the April / May 2015 and October 2016 overflows.

Source: HVO - USGS

Kilauea - the widest overflow (silver gray color) north of crater Overlook 23.04.2018 - photo HVO-USGS

Kilauea - the widest overflow (silver gray color) north of crater Overlook 23.04.2018 - photo HVO-USGS

In Nicaragua, currently rocked by demonstrations, the San Cristobal volcano has shown a strong activity this Sunday, April 22, 2018 at 13:30, characterized by unbegazage followed by emission of ashes. Ineter did not report this activity, which remains typical of the volcano.

Source: TN8 / Twitter

San Cristobal - ash emission in the evening  - photo  archives TN8 / Twitter

San Cristobal - ash emission in the evening - photo archives TN8 / Twitter

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