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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

The day of April 12 at La Soufrière in St. Vincent was marked by a huge explosions at 4:15 am, which was accompanied by a plume of ash and gas reaching an altitude of 17-18 km., And density currents. pyroclastic descending several valleys on the southern and western flanks of the volcano. They reached the sea at Morne Ronde, Larikai and Trois Loupes Bay and caused extensive damage to vegetation.

The amplitude of the tremor has changed since April 11 around noon, with a lengthening of the time between high amplitude episodes at 5-8 hours; Around 6 p.m. on April 11, small volcano-tectonic earthquakes were recorded. On April 12, 3 episodes of tremor were recorded for 6 hours, coinciding with periods of explosive activity or increased venting.

Soufrière de St. Vincent 11.04.2021 - SO2 over SV and Barbados, then over the Atlantic to the coasts of West Africa - Doc. Sentinel -5P tropomi

Soufrière de St. Vincent 11.04.2021 - SO2 over SV and Barbados, then over the Atlantic to the coasts of West Africa - Doc. Sentinel -5P tropomi

Soufriere of St. Vincent - volcanic plume of 12,04,2021 / 4:15 local reaching the stratosphere; its top is measured at -80 ° - GOES 16 IR satellite image

Soufriere of St. Vincent - volcanic plume of 12,04,2021 / 4:15 local reaching the stratosphere; its top is measured at -80 ° - GOES 16 IR satellite image

Comparative analysis of satellite images shows that the explosions destroyed the pre-existing 1979 and 2020-2021 domes, and suggests the existence of a new vent in the new crater.

Soufriere de St. Vincent - image 04.12.2021 / 09:50 Image Sentinel-1 SAR intensity - UWI comment: possible new vent in the new crater. The black areas on the western flank of the volcano (on the left) correspond to the area affected by the deposits of pyroclastic flows - Doc. Sentinel / ESA - Copernicus, via Mounts project

Soufriere de St. Vincent - image 04.12.2021 / 09:50 Image Sentinel-1 SAR intensity - UWI comment: possible new vent in the new crater. The black areas on the western flank of the volcano (on the left) correspond to the area affected by the deposits of pyroclastic flows - Doc. Sentinel / ESA - Copernicus, via Mounts project

Soufrière de St. Vincent - 10.04.2021 / 12h10 - SAR image penetrating the ash and gas plumes and revealing the destruction of the pre-existing domes - Doc. Capella Space

Soufrière de St. Vincent - 10.04.2021 / 12h10 - SAR image penetrating the ash and gas plumes and revealing the destruction of the pre-existing domes - Doc. Capella Space

Time line of the Soufrière eruptions and their type of explosive and / or effusive activity - Doc. Paul Cole and Vincie Richie - Note the last activity period: 27.12.2020 to 13.04.2021 / in progress (GVP) - one click to enlarge

Time line of the Soufrière eruptions and their type of explosive and / or effusive activity - Doc. Paul Cole and Vincie Richie - Note the last activity period: 27.12.2020 to 13.04.2021 / in progress (GVP) - one click to enlarge

Explosions, accompanied by falling ash and pyroclastic flows, are likely to occur over the next few days.

 

Sources: UWI-SRC & NEMO SVG

Piton de La Fournaise - the eruptive site and its vents active on 04.12.2021 - photo OVPF

Piton de La Fournaise - the eruptive site and its vents active on 04.12.2021 - photo OVPF

The eruption of Piton de La Fournaise, which began on 04/09/2021 at 7 p.m. (appearance of the tremor), continues.

The intensity of the volcanic tremor (indicator of the intensity of the eruption) over the last 24 hours has been very fluctuating.

These fluctuations can be linked to either:

- the cone under construction which undergoes construction and dismantling phases, thus influencing the speed of the lava flows at the level of the vent;

- or to punctual releases of pockets of gas trapped in the supply ducts which can be released suddenly causing an increase in the tremor with a certain periodicity.

Over the last 24 hours, 31 superficial volcano-tectonic earthquakes (between sea level and the surface) have been recorded under the summit craters.

Piton de La Fournaise - location of the active vents in the Enclosure on 04.12.2021 / 6:16 p.m. - IRT / IPGP-OVPF webcam - a click to enlarge

Piton de La Fournaise - location of the active vents in the Enclosure on 04.12.2021 / 6:16 p.m. - IRT / IPGP-OVPF webcam - a click to enlarge

Piton de La Fournaise - location of active vents in the Enclosure on 04/13/2021 / 10:17 am - IRT / IPGP-OVPF webcam - a click to enlarge

Piton de La Fournaise - location of active vents in the Enclosure on 04/13/2021 / 10:17 am - IRT / IPGP-OVPF webcam - a click to enlarge

Observations of the eruptive site always show two eruptive mouths, a main and a secondary of lower activity slightly downstream. The height of the lava fountains emitted by the main mouth fluctuates between 20 and 60 meters depending on the period of activity.

On the evening of April 12, the flow front was located in the Piton le Bonnet sector at an altitude of around 1500-1550m, the flow had thus traveled about 3.6 km since the start of the eruption.

The plume of gas directed towards the south and the west made it possible to record for the day yesterday SO2 flows of between 4 and 5 kilotons / day on the NOVAC stations of the OVPF-IPGP located on the periphery of Enclosure, while flows of the order of 2-4 kilotons / day were recorded between April 9 and 11.

The surface flows estimated from satellite data via the HOTVOLC platform (OPGC - Clermont Auvergne University) remain very disturbed by the cloud cover on the eruptive site with values ​​between 8 and 30 m³ / s since the start of the eruption .

 

Source: OVPF-IPGP press release

Piton de La Fournaise 04.12.2021 - lava flows have reached the major slopes - Doc. OVPF - one click to enlarge

Piton de La Fournaise 04.12.2021 - lava flows have reached the major slopes - Doc. OVPF - one click to enlarge

In order to avoid groupings conducive to the spread of the virus and the appearance of chains of contamination and to ensure compliance with curfew measures, the practice of camping and bivouacs is prohibited from April 13, on the entire territory ... (visits should only be done during the day!)

 

Source: Prefecture of Reunion

Piton de La Fournaise - ban on bivouacs from 13.04.2021 / Covid measures / Reunion Prefecture

Piton de La Fournaise - ban on bivouacs from 13.04.2021 / Covid measures / Reunion Prefecture

In the Reykjanes Peninsula, the latest lava flow size and lava flow data at Fagradalsfjall are based on the April 12 afternoon flight.

The results show that the total flow from all craters over the past four days has averaged nearly 5 m³ / s. It's almost equal to the average bitrate from the start. It seems that the increase that took place last week, alongside the opening of new craters, was rather short-lived. The lava area has increased relatively little in recent days, as the recently formed magma mostly started to increase the thickness of the lava. The total volume now exceeds just over 10 million cubic meters.

 

Source: University of Iceland - Jarðvísindastofnun Háskólans

Eruption at Fagradalsjfall - parameters as of 12.04.2021 - Doc. Jarðvísindastofnun Háskólans - one click to enlarge

Eruption at Fagradalsjfall - parameters as of 12.04.2021 - Doc. Jarðvísindastofnun Háskólans - one click to enlarge

Lava thickness at Meradalir, southwest Iceland, April 10, 2021. Based on drone images obtained with Matrice 300 RTK (Sigurður Helgason DJI), and further processing to obtain a digital surface model ( DSM) and an orthomosaic. Comparison with pre-eruption high-resolution digital elevation models (DEM) allows the thickness of the lava to be calculated. The data provides additional information on the properties and flow of lava.

Lava thickness at Meradalir, southwest Iceland, April 10, 2021. Based on drone images obtained with Matrice 300 RTK (Sigurður Helgason DJI), and further processing to obtain a digital surface model ( DSM) and an orthomosaic. Comparison with pre-eruption high-resolution digital elevation models (DEM) allows the thickness of the lava to be calculated. The data provides additional information on the properties and flow of lava.

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