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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 : #volcanic activity
Meradalur - degassing observed on 08.20.2022 / 1:55 p.m. - visir webcam - one click to enlarge

Meradalur - degassing observed on 08.20.2022 / 1:55 p.m. - visir webcam - one click to enlarge

Activity at the Meradalur vents and associated tremor has been gradually decreasing over the past three days, so much so that by Saturday afternoon, no fountains were visible at the vents and the tremor was almost non-existent . However, there is always a regular evacuation of magmatic gases.

Around 8 p.m., the eruption of Meradalur was reported to be still alive, although its power had been reduced considerably, with incandescence visible in the crater. In the evening, we could see a slight spattering in a small opening inside the main crater and still a lot of degassing. Additionally, a small river of lava infiltrates the surface southeast into the valley. The lava river has no direct connection to the crater, but a lot of degassed lava flows to the surface through a closed channel (lava tunnel) a little to the east of the crater. This was confirmed by ENSu with images from drones that flew over the area.

The tremor fell stronger on August 21 in the morning.

Meradalu eruption - The falling tremor at the Fagradalsfjall station on 21.08.2022 - Doc. Hraun.vedur

Meradalu eruption - The falling tremor at the Fagradalsfjall station on 21.08.2022 - Doc. Hraun.vedur

This trend in eruptive behavior is very different from that observed at the end of the individual eruptive episodes of the 2021 eruption, which ended very abruptly. Therefore, it is likely that this rather slow and gradual decline in activity will mean the end of Meradalir's eruption in 2022.

Meradalur - lava field on 16.08.2022 - Doc. Jardvis.hi.is/meradalir_hraun_2022-08-16_thykkt_utbreidsla_1 - one click to enlarge

Meradalur - lava field on 16.08.2022 - Doc. Jardvis.hi.is/meradalir_hraun_2022-08-16_thykkt_utbreidsla_1 - one click to enlarge

The image of the 2022 lava field, as of 08.16.2022, shows the outline of the new lava (purple line) and its thickness. At the crater, the thickness is in many places from 20 to 30 meters and up to 40 m. at the edges of the crater. At Meradälur outside the crater area, the thickness is in most places 5 to 15 meters. The total volume is estimated at 12 million cubic meters, which represents about 8% of the material that emerged during the eruption last year. (Jardvis.hi.is)

 

Sources: Eldfjallafræði og náttúruvárhópur Háskóla Íslands, Visir webcam, Jardvis.hi.is, Brett Carr.

Merapi - seismicity and deformation on 08.20.2022 - Doc. BPPTKG - one click to enlarge

Merapi - seismicity and deformation on 08.20.2022 - Doc. BPPTKG - one click to enlarge

At Merapi, on Java, the volcano is clearly visible until it is covered by fog 0-III. The smoke observable from the main crater is white with fine to medium high intensity about 10-20 meters from the summit. The weather is sunny to cloudy, the wind is light to moderate from the west.

The seismicity of August 20 was characterized by:
- 67 avalanche earthquakes, with an amplitude of 3-31 mm and an earthquake duration of 23.6-190.1 seconds.
- 4 blast / emission earthquakes, with an amplitude of 3-4 mm and the duration of the earthquake from 15.5 to 21.8 seconds.
- 80 hybrid/multiphase earthquakes, with an amplitude of 3-27 mm, S-P 0.4-0.6 seconds and an earthquake duration of 4.2-9.6 seconds.
- 1 shallow volcanic earthquake, with an amplitude of 68 mm and an earthquake duration of 11.4 seconds.
- 1 distant tectonic earthquake with an amplitude of 5 mm, and the duration of the earthquake was 48.3 seconds.

 

Activity level remains at 3/siaga

 

Sources: PVMBG, Magma Indonesia, BPPTKG

Samoa islands - View of part of the tuff cone containing both the village of Faleāsao and the port of Faleasao from the island of Taʻū, American Samoa. - photo USGS 19.08.2022 - one click to enlarge

Samoa islands - View of part of the tuff cone containing both the village of Faleāsao and the port of Faleasao from the island of Taʻū, American Samoa. - photo USGS 19.08.2022 - one click to enlarge

On Friday, Aug. 19, the U.S. Geological Survey's Hawaiian Volcanoes Observatory raised the alert level for the previously unassigned Taʻu Island to "Yellow/Advisory," as a swarm of earthquakes continues to rock the Manuʻa Islands of American Samoa.
This designation does not reflect a change in the behavior of either volcano, according to the HVO, it simply acknowledges that the number, size and frequency of earthquakes experienced by the inhabitants of the island of Taʻū and Ofu-Olosega are well above average/background activity.


Instruments installed over the past week confirm continued high seismic activity. The latest data, obtained from rapidly deployed microseismometers, indicates that the source is closer to Taʻū than to Olosega and not close to Vailuluʻu. The earthquake swarm is most likely due to the movement of magma under the volcanoes and not tectonic faults.

 

Source: HVO, via Big islands news, article of 18.08 on this blog

The volcanic islands of American Samoa - Doc. USGS 19.08.2022 - one clic to enlarge

The volcanic islands of American Samoa - Doc. USGS 19.08.2022 - one clic to enlarge

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