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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
Agung - eruptive plume rising to 1,500 m in height on 13.02.2018 / 11:49 AM WITA - photo Devay Natamanggala

Agung - eruptive plume rising to 1,500 m in height on 13.02.2018 / 11:49 AM WITA - photo Devay Natamanggala

An update on Agung's activity thanks to information from PVMBG and BNPB.

During the past month, the frequency of eruptive incidents has decreased according to the observations, the last eruption is reported by the observatory on January 24, 2018.

The volume of the lava dome has not changed significantly, and is still estimated at 20 million cubic meters, or 1/3 of the empty volume of the crater.

Inflation is still observed, but characterized by a lower ratio, indicating that pressurization following magmatic movements is less significant.
 

Agung crater - between 20.10.2017 and 10.02.2018 -photo drone PVMBG

Agung crater - between 20.10.2017 and 10.02.2018 -photo drone PVMBG

Measurement of magmatic gases still indicates the existence of deep magma movement dynamics, while magmatic carbon dioxide concentrations are lower than those measured before the November 2017 eruption. The sulfur dioxide flux is relatively low, either due to the dissolution of the gases in the water, or due to a smaller surface diet. The CO2 / SO2 ratio, which reflects the intensity of magmatic activity, shows a downward trend compared to November 2017.

The volume of magma circulating inside the volcano is currently less than one million m³, 40 times lower than in September-November 2017, where it was estimated at 40 million m² ... which implies a decrease the opportunity of major eruptions.

The satellite data show a decrease in the thermal energy of the crater, and confirm a decrease in the ratio of lava flow to the surface. The dome surface hardens, with a potential for increased pressure, followed by strombolian eruption as occurred on January 19, 2018.

Agung - height of plumes between 1 ° November 2017 and 10 February 2018 - doc.PVMBG

Agung - height of plumes between 1 ° November 2017 and 10 February 2018 - doc.PVMBG

Agung - Seismicity on 12.02.2018 - Doc.Magma Indonesia

Agung - Seismicity on 12.02.2018 - Doc.Magma Indonesia

On the basis of these multiple parameters, the PVMBG concludes that Agung volcanic activity is still high and unstabilized, with the possibility of an eruption at any time.

However, the alert level was lowered on February 10 from level IV / Awas to level III / Siaga, with a 4 km radius hazard zone. There are still more than 15,000 displaced people, despite the authorized returns.

 

Yesterday, February 12, the seismicity was characterized by 7 emission earthquakes, an episode of harmonic tremor, 5 superficial volcanic earthquakes VB, 7 deep volcanic earthquakes VA and a tectonic earthquake.

This February 13 at 11:49 local, a plume of ash and gas was observed at 1,500 meters above the summit

Sources: PVMBG & BNPB data

Agung - eruptive plume of 13.02.2018 / 11:49 AM WITA - photoBNPB

Agung - eruptive plume of 13.02.2018 / 11:49 AM WITA - photoBNPB

According to E.Duarte, a volcanologist of Ovsicori, the acidic lake of Poas, measured at a pH between 0 and 1, reached a depth of maximum 15 meters, since according to his observations, he covers and will disintegrate the "red cone" visible in September 2017. Its temperature in the hottest areas is 97 ° C, and accompanied by sound emissions of steam and gas. On its edges, bubbles of sulfur are formed in abundance.

Duarte finds a balance between energy, temperature and pressure; which gives an aspect of calm comparable to that which he possessed before the eruptive cycle which began a little before the holy week in 2017.

Poas - acid lake; in the box, situation on 04.09.2017 - photo Ovsicori / via La Nacion 13.02.2018

Poas - acid lake; in the box, situation on 04.09.2017 - photo Ovsicori / via La Nacion 13.02.2018

The acidic lake of Poas has dried up in the past several times: in 1989, where it filled up after six weeks; in 1994, after which it lasted 23 years, reaching its greatest depth with 36 meters. The presence of the ancient dome made it a long barrier, preventing it from filling the crater in the rainy season.

After the eruption of 2017, the waters took nine months to cover the bottom of the crater.

Sources: Ovsicori, RSN, La Nacion

The crater of Turrialba under the passive emissions of ash on 12.02.2018, during a visit of the teams of the RSN - Photographs of Jean Paul Calvo and Alexandre Argüello.

The crater of Turrialba under the passive emissions of ash on 12.02.2018, during a visit of the teams of the RSN - Photographs of Jean Paul Calvo and Alexandre Argüello.

At Turrialba, the RSN teams visited the crater on 12 February for monitoring and maintenance works. The passive ash emissions of the last days had covered the solar panels supplying electronics, as well as the internal walls of the crater and the vegetation.

The crater of Turrialba and the vegetation under the passive emissions of ash on 12.02.2018, during a visit of the teams of the RSN - Photographs of Jean Paul Calvo and Alexandre Argüello. - a click to enlarge
The crater of Turrialba and the vegetation under the passive emissions of ash on 12.02.2018, during a visit of the teams of the RSN - Photographs of Jean Paul Calvo and Alexandre Argüello. - a click to enlarge
The crater of Turrialba and the vegetation under the passive emissions of ash on 12.02.2018, during a visit of the teams of the RSN - Photographs of Jean Paul Calvo and Alexandre Argüello. - a click to enlarge

The crater of Turrialba and the vegetation under the passive emissions of ash on 12.02.2018, during a visit of the teams of the RSN - Photographs of Jean Paul Calvo and Alexandre Argüello. - a click to enlarge

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