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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
Merapi summit, seen from the SW in the fog on 25.08.2021 - photo- Andi volcano

Merapi summit, seen from the SW in the fog on 25.08.2021 - photo- Andi volcano

From August 20 to 26, at Merapi on Java, there were 2 pyroclastic flows in the southwest with a maximum glide of 2,000 m. Incandescent boulder falls have been observed 211 times to the southwest with a maximum sliding distance of 2,000 m.

Morphological changes are observable in the southwest lava dome, the height of the dome has increased by about 3 m., While the central dome is relatively fixed.

The volume of the southwest lava dome is 1,400,000 m³ and the central dome is 2,831,000 m³.

The current potential danger consists of lava avalanches and hot clouds in the southeast-southwest sector for a maximum of 3 km to the Woro River, and 5 km to the Gendol, Kuning, Boyong rivers. , Bedog, Krasak, Bebeng and Putih. the ejection of volcanic material in the event of an explosive eruption can reach a radius of 3 km from the summit.

 Merapi - risk maps at 25.08.2021 - Doc. BPPTKG

Merapi - risk maps at 25.08.2021 - Doc. BPPTKG

Merapi - seismicity of the week and number of earthquakes on 08/27/2021 - Doc. BPPTKG

Merapi - seismicity of the week and number of earthquakes on 08/27/2021 - Doc. BPPTKG

On August 27, the seismicity changed facies with:

- 1 pyroclastic flow collapse earthquake, with an amplitude of 75 mm and a duration of 150 seconds.
- 262 collapse / avalanche earthquakes, with an amplitude of 3-43 mm and an earthquake duration of 12-136 seconds.
- 494 blast / emission earthquakes, with an amplitude of 3 to 6 mm and an earthquake duration of 7 to 43 seconds.
- 48 low frequency earthquakes, with an amplitude of 3 to 8 mm and an earthquake duration of 9 to 20 seconds.
- 48 hybrid / multiphase earthquakes, with an amplitude of 3 to 24 mm, S-P from 0.3 to 0.7 seconds and a duration of 6 to 17 seconds.
- 2 distant tectonic earthquakes.

The activity level remains at 3 / siaga.

 

Source: BPPTKG

Rincon de La Vieja - 08.28.2021 - photo Ovsicori

Rincon de La Vieja - 08.28.2021 - photo Ovsicori

Three small phreatic eruptions were recorded on August 27, 2021 at Rincon de La Vieja, respectively at 19:15, 20:49 and 20:53 local time. The most important happened at 8:49 p.m. There was no visibility, no report. Duration of the activity: 2 minutes.

At 2:46 p.m. local time on August 28, 2021, a phreatic eruption was recorded at the Rincon de la Vieja volcano, with a column that rises 1,000 meters above the height of the crater and 2,916 m above sea level. altitude. At the time of this report, the winds are blowing from the southwest.
Duration of activity: 1 minute.
Seismic activity is higher than yesterday.
The amplitude of the tremor increased after this event in particular in the low frequencies of approximately 1 hour at the beginning of the night. Until the moment of this report, the tremor remains with a greater amplitude than the day before.

 

Source: Ovsicori

Kilauea - Halema'uma'u crater - USGS photo by M. Patrick

Kilauea - Halema'uma'u crater - USGS photo by M. Patrick

The Kīlauea volcano is not erupting. However, intrusive activity, which began on August 23, continues south of the Kīlauea caldera.

From the evening of August 26, soil deformation in the southern summit region of Kīlauea resumed at the highest rates seen during the first intrusive pulse spanning August 23 to 25. On the other hand, the current seismic activity remains low compared to the previous impulses of this intrusive activity. The East Rift Zone remains calm.
The rate of soil deformation under the southern portion of the Kīlauea Summit region in Hawai'i Volcanoes National Park began to increase again on the evening of August 26 and continues to this time. These observations suggest that magma continues to fuel the ongoing intrusion.

In the past 24 hours, around 80 earthquakes have been recorded at the top of Kīlauea and south of the Kīlauea caldera. Most of the earthquakes were less than magnitude 2 and occurred about 1 to 4 km (0.6 to 2.5 mi) below the surface. These small earthquakes occurred at a frequency of up to 7 detected earthquakes per hour. These earthquake rates are significantly lower than the rates seen earlier this week.

Activity continues, but there is no indication of upward migration of earthquakes to the surface or change in deformation that would indicate a decrease in the depth of source intrusive activity. As a result, Kīlauea's Volcanic Alert Level and Aviation Color Code remain at Advisory / Yellow.

 

Source: HVO

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