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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
Soufrière de St. Vincent - hot spot on this Sentinel-2 image from 04.23.221 - Doc. Copernicus / ESA via CDEMA - one click to enlarge

Soufrière de St. Vincent - hot spot on this Sentinel-2 image from 04.23.221 - Doc. Copernicus / ESA via CDEMA - one click to enlarge

The seismic activity at La Soufrière de St Vincent has remained weak since the earthquake associated with the explosion and release of ash around noon on April 22.
In the past 24 hours, only a few long-period hybrid and volcano-tectonic earthquakes have been recorded and there have been no other earthquakes.
Since the initial depressurization seen immediately after the explosive phase of April 9, the continuous GPS network has recorded a decrease in overall rates of movement.
The eruption continues: a “hot spot” is visible on a Sentinel-2 image (Doc. Raphael Grandin, IPGP); its pattern of seismic activity over the past few days is typical of the growth and destruction of lava domes.
Explosions accompanied by falling ash, of a similar or greater magnitude, may occur with little or no warning.
The volcano is at the Red alert level.

 

Sources: UWI-SRC Scientific update La Soufrière, St. VIncent - 04/24/21 6:00 p.m. & CDEMA

Soufrière de St. Vincent - Total destruction of farms on Richmond mountain on the road to Trinity Falls - photo Toosie 04.23.2021 / UWI-SRC

Soufrière de St. Vincent - Total destruction of farms on Richmond mountain on the road to Trinity Falls - photo Toosie 04.23.2021 / UWI-SRC

Soufrière of St. Vincent - Total destruction of farms on Richmond mountain - note the thickness of hardened ash on the roof -photo Toosie 04.23.2021 / UWI-SRC

Soufrière of St. Vincent - Total destruction of farms on Richmond mountain - note the thickness of hardened ash on the roof -photo Toosie 04.23.2021 / UWI-SRC

Details of the eruption in the Reykjanes Peninsula and the eruptive fields in Geldingadalur and Meradalur, with an aerial view by Volcano Chaser of the eruption site, with the current state of fissure activity. Keilir is visible on the far left.
The photo was taken on April 20, but nothing major has changed since.

Reykjanes Peninsula - 04.20.2021 - Aerial view of the eruption site with the current state of crack activity. Keilir is visible on the far left. - photo Volcano chaser via Oroapuls - one click to enlarge

Reykjanes Peninsula - 04.20.2021 - Aerial view of the eruption site with the current state of crack activity. Keilir is visible on the far left. - photo Volcano chaser via Oroapuls - one click to enlarge

Description of the photo by Volcano Chaser:

Crack 1.
Open at 8:45 p.m. on March 19. Two vents are still active, even though activity has dropped steadily over the past 10 days. The North Vent feeds into the Geldingadalir Lava Field, which thickens and expands west and south primarily with small, ephemeral vents that open at the edge of the field itself.

Crack 2 - Inactive.
Open around 11:45 am on April 05 - The eruption ceased on April 18.
Activity at Fissure 2 declined just before the opening of Fissure 5, but declined more steadily between April 16 and April 17. No more activity has been observed since the evening of April 18.

Crack 3.
Open at midnight on April 07.
Activity here increased in the late afternoon of April 13. It has since become quite stable.

Crack 4 - Inactive.
Open at 3:13 am April 10 - The eruption ceased on April 13. The activity here suddenly waned 45 minutes before the crack 5 opened. By the evening of April 13, no activity was visible.

Fissure 5S (south) -
Open at 8:37 a.m. on April 13. Activity here has been fairly stable over the past 10 days, with minor fluctuations. Within the first 24 hours, the crack merged into two main vents, both still active. The lower vent produces the lava flow that stretches east out of Geldingadalir.

Crack 5N (North) -
Open at 8:51 am on April 13. This is the crack that most people like to call "crack 6". In my opinion this is a segment of crack 5, opened in the same fissure episode.
The crack merged into a main vent within the first 24-36 hours and has been fairly stable since it started to burst.

Reykjanes Peninsula - seismicity and other parameters at 04/22/2021 / 1:30 p.m. - Doc. One.Iceland

Reykjanes Peninsula - seismicity and other parameters at 04/22/2021 / 1:30 p.m. - Doc. One.Iceland

New results on the chemical composition of magma ...
The chemical composition of the magma that erupts at Geldingadalur and flows towards Meradalur has changed over time.

Now, more than a month has passed since the start of the eruption, the ratio of K2O / TiO2 compounds in the magma has increased.
These changes are believed to indicate that the magma that is now emerging is coming from an even greater depth in the Earth's mantle than that which came at the start of the eruption. This change is also considered to indicate that the magma was formed by a smaller melting of the mantle, compared to the magma that appeared at the start of the volcanic eruption.

New results on gas emissions from the lava flow:
Gas emissions are estimated from the lava flow. It's similar to what it was, 4000-6000 tonnes / day of CO2, 2000-3000 tonnes / day of SO2 and 4-5 tonnes / day of fluoric acid.

 

Source: Edward Marshall, scientist in the Department of Earth Sciences, University of Iceland.

http://jardvis.hi.is/eldgos_i_fagradalsfjall

Pacaya - degassing at the Mackenney cone and still hot / glowing lava flow - image Sentinel-1 bands 12,11,8A from 04.19.2021 / 4:18 p.m. - one click to enlarge

Pacaya - degassing at the Mackenney cone and still hot / glowing lava flow - image Sentinel-1 bands 12,11,8A from 04.19.2021 / 4:18 p.m. - one click to enlarge

The eruptive phase that began in Pacaya on February 5, 2021 has ended, according to Insivumeh.

From February 5 to mid-March, the behavior of the volcano was mainly explosive, with the emission of ash and lapilli affecting the surrounding communities.

From March 20, following the opening of a crack on the southwest flank, the activity became more effusive: the lava flows reached the communities of El Patrocinio and El Rodeo.

 

The seismic activity associated with the lava effusion has been decreasing since April 16. The lava flows, the longest of which extended over approximately 3,800 m. in length, no longer showing progression in any direction; the lava solidified 450 meters from the first houses, and remains hot, with degassing fumaroles.

The Mackenney crater only presents a degassing plume (water vapor and sulfur dioxide), containing little ash, at a height of 3,000 m. asl. and a few weak sporadic explosions.

 

Source: Insivumeh

 Sakurajima  - 25.04.2021  / 01h12 - webcam  JMA

Sakurajima - 25.04.2021 / 01h12 - webcam JMA

An explosion occurred at Sakurajima Minamidake crater on April 25 at 1:09 am, accompanied by a plume that rose to 2,300 m. above the rim of the crater, and first described as generating a pyroclastic flow to the southwest.

A field survey carried out by the JMA mobile team found no trace of this pyroclastic flow, nor of any particular change around the summit crater.

Level is 3 / entry restrictions into hazardous areas such as climbing bans and climbing restrictions.

 

 

Source: JMA / Kagoshima Local Meteorological Observatory

Sakurajima / Kaigata surveillance camera -  the eruptive plume rose 2300 m above the crater rim and flowed southwest. Pyroclastic flow from the crater to the southwest side (not confirmed by site visits) - Doc. JMA

Sakurajima / Kaigata surveillance camera - the eruptive plume rose 2300 m above the crater rim and flowed southwest. Pyroclastic flow from the crater to the southwest side (not confirmed by site visits) - Doc. JMA

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