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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
 Turrialba - eruptive episode of 08/01/2020 / 8:59 am - Ovsicori webcam

Turrialba - eruptive episode of 08/01/2020 / 8:59 am - Ovsicori webcam

Turrialba - eruption of 07/16/2020 / 12:09 p.m. - Ovsicori webcam

Turrialba - eruption of 07/16/2020 / 12:09 p.m. - Ovsicori webcam

After a multi-year activity, the Turrialba had not expelled any ash since November 2019.

The activity resumed since June 2020 with small eruptions, then on July 30 and 31, various eruptive episodes followed one another, with columns of gas and ash reaching 200 meters above the summit. On August 1, the plume of gas and ash reached 500 meters above the crater.

Source: Ovsicori

Popocatépetl - incandescence on August 1, 2020 / 9:12 p.m. and August 2 / 2:38 a.m. - Doc. webcams from Mexico
Popocatépetl - incandescence on August 1, 2020 / 9:12 p.m. and August 2 / 2:38 a.m. - Doc. webcams from Mexico

Popocatépetl - incandescence on August 1, 2020 / 9:12 p.m. and August 2 / 2:38 a.m. - Doc. webcams from Mexico

During the last 24 hours, 10 exhalations have been identified with Popocatépetl, accompanied by volcanic gases and sometimes small amounts of ash.

In addition, 1159 minutes of tremors were recorded, sometimes accompanied by incandescent fragments that fell a short distance from the crater.

During the night, an incandescence could be observed above the crater during short periods of clearing, with fallout of fragments in the crater

In the morning of August 2, it was possible to observe a constant emission of gas, light ash which dispersed towards the west-southwest.

 

Sources: Cenapred and WebcamsdeMexico

Popocatépetl - ash emission on August 2/9 a.m. - WebcamsdeMexico

Popocatépetl - ash emission on August 2/9 a.m. - WebcamsdeMexico

At Piton de La Fournaise, the resumption of seismicity and inflation since June 16, as well as the high fluxes of CO2 in the soil (despite a downward trend) were signs of a resumption of pressurization of the superficial magmatic reservoir and its recharge by deep magmas, which triggered the July 3 intrusion. Since the July 3 intrusion, seismic activity has remained low and inflation has stopped around July 13

In July, OVPF recorded at the level of the Piton de la Fournaise massif a total of 224 superficial volcano-tectonic earthquakes (0 to 2.5 km deep) under the summit craters; 2 deep earthquakes (2.5 to 5 km deep); 247 collapses (in the Crater Dolomieu and at the ramparts of the Enclos Fouqué and the Rivière de l'Est).

Piton de La Founaise - Illustration of the deformation over the last six months (eruptive and intrusive periods are shown in red and green respectively). The variations in distance between two GPS receivers crossing the Piton de la Fournaise building, at the top (reference BOMG; above), at the base of the terminal cone (reference FJAG; in the middle) and in the far field (reference PRAG; bottom) (see location in Figure 6). A rise is synonymous with elongation and therefore swelling of the volcano; conversely, a decrease is synonymous with contraction and therefore deflation of the volcano (© OVPF-IPGP)

Piton de La Founaise - Illustration of the deformation over the last six months (eruptive and intrusive periods are shown in red and green respectively). The variations in distance between two GPS receivers crossing the Piton de la Fournaise building, at the top (reference BOMG; above), at the base of the terminal cone (reference FJAG; in the middle) and in the far field (reference PRAG; bottom) (see location in Figure 6). A rise is synonymous with elongation and therefore swelling of the volcano; conversely, a decrease is synonymous with contraction and therefore deflation of the volcano (© OVPF-IPGP)

The volcano-tectonic activity under the summit of Piton de la Fournaise in July 2020 will have been mainly marked by the seismic crisis of July 3 (197 superficial volcano-tectonic earthquakes between 3:20 and 3:55 UT. These earthquakes were located under the southern part of the Dolomieu crater between 1.7 and 2.2 km deep, and have been associated with an intrusion of magma which left the superficial magmatic reservoir and which stopped at depth before reaching the surface. magmatic of July 3, the summit volcano-tectonic activity remained weak with an average of less than one superficial volcano-tectonic earthquake per day. Note that the OVPF again recorded many (210) collapses in the broke from the East River in July 2020.

The inflation (swelling) of the edifice which had resumed around June 16 continued until around July 13. Thus between June 16 and July 13 an elongation of about 3 cm max. of the summit area and an elongation of approximately 3.75 cm max. of the base of the terminal cone were recorded. Numerical models of these deformations show during this period the activation of a pressure source around 1-1.5 km deep under the Dolomieu crater, corresponding to the pressurization of the superficial magmatic reservoir. The deformations linked to the July 3 magmatic intrusion were of very low intensity (less than 0.5 cm) and were only visible on the data from the inclinometric stations (with a maximum slope variation of 4 µradians.

 

Source: OVPF

Kilauea - evolution from the pond to a lake in the Halama'uma'u crater - Doc. USGS

Kilauea - evolution from the pond to a lake in the Halama'uma'u crater - Doc. USGS

At the top of Kilauea, a lake ... of water has existed for a year.

Isotope analysis indicated that the water was originally from precipitation. Most of it comes from groundwater (precipitation that has seeped into the ground) which seeps where the water table crosses the crater.

Kilauea - Halema'uma'u lake on 02.08.2019 and 21.07.2020 - Doc. USGS

Kilauea - Halema'uma'u lake on 02.08.2019 and 21.07.2020 - Doc. USGS

On July 25, 2019, accumulated water was observed for the first time in Halema'uma'u at the top of the Kīlauea volcano. Over the past twelve months, the USGS Hawaiian Volcano Observatory (HVO) has observed this astonishing body of water shift from a nascent pond to a real lake, the first seen in the Kīlauea Caldera in at least 200 years.

The HVO closely monitors the lake using a variety of methods. Visual and thermal cameras monitor the color and temperature of the lake's surface. The color is variable and the lake surface temperature is warm, always around 70–85 ° Celsius).

The laser range finder measurements track the level of the surface, which has steadily increased by about 2.5 feet (0.75 m) each week. And two dedicated water sampling missions were carried out using drones.

Over time, minerals and volcanic gases dissolve in the water and the chemistry of the lake changes. When the lake first formed, it was a light blue-green color, a color that can still be seen in parts of the lake where the influx is higher. The surface water is mostly shades of orange and brown now, possibly due to the dissolved iron-rich sulphate minerals. The water in the lake is not evenly mixed, and water cells of different colors, chemistry and temperature circulate.

As well as being rare due to its very existence, this lake is unique in that it is only slightly acidic, with a pH of around 4.0, while most volcanic lakes are either strongly acidic. , or strongly alkaline. For reference, orange juice is also slightly acidic with a pH of 3.5. The acidity of the water is probably moderate at this early stage of development, and it may become more acidic in the future.

After a year of steady growth, the lake now covers an area of ​​over 2.5 hectares and reaches a depth of over 40 m. Its volume exceeds 473 million liters of water, or nearly 200 Olympic swimming pools!

 

Source: USGS

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