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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
Piton de La Fournaise - The Dolomieu examined by the teams of the OVPF - photo early September 2019

Piton de La Fournaise - The Dolomieu examined by the teams of the OVPF - photo early September 2019

Since October 11, a recovery of seismicity is observed under the Piton de la Fournaise. Thus, 36 superficial volcano-tectonic earthquakes (<2 km below the summit) were recorded under the summit zone between 11 and 15 October. More profound earthquakes are also recorded (under the summit and under the east flank).

Piton de La Fournaise - Histogram representing the number of superficial volcano-tectonic earthquakes recorded between October 1 and October 15, 2019 (© OVPF-IPGP).

Piton de La Fournaise - Histogram representing the number of superficial volcano-tectonic earthquakes recorded between October 1 and October 15, 2019 (© OVPF-IPGP).

This seismicity is accompanied by a resumption of inflation (swelling) of the base and the top of the Piton de la Fournaise building. This inflation of the building is synonymous with a pressurization of the superficial magma reservoir located about 2-2.5 km below the summit.

Piton de La Fournaise - Illustration of the deformation over the last two months. Bases are shown here (variation of distance between two GPS receivers) crossing the Piton de la Fournaise building, at the top (at the top), at the base of the terminal cone (in the middle) and in the far field (at the bottom ). 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 Fournaise - Illustration of the deformation over the last two months. Bases are shown here (variation of distance between two GPS receivers) crossing the Piton de la Fournaise building, at the top (at the top), at the base of the terminal cone (in the middle) and in the far field (at the bottom ). 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).

In parallel, CO2 concentrations in the soil are still decreasing in the far field (Plaine des Cafres and Plaine des Palmistes sectors) and in slight increase in the proximal zone (Gite du Volcan). These evolutions of CO2 concentrations are in agreement with a deep rise of magma from the deep zones (decrease of the concentrations in distal zone) towards the superficial reservoir (increase of the concentrations in proximal zone).
Note that this process of recharging the superficial reservoir can take several days to several weeks before the roof of the tank becomes brittle and breaks, giving rise to an injection of magma towards the surface and an eruption, but can also stop without giving rise to an eruption in the short term.

 

Source: OVPF - Find all the information related to the activity of the Piton de la Fournaise on the different media of the OVPF-IPGP:
- the website (http://www.ipgp.fr/fr/ovpf/actualites-ovpf),
- the Twitter account (https://twitter.com/obsfournaise?lang=en),
- and the facebook account (https://www.facebook.com/ObsVolcanoPitonFournaise/)

Bogoslof - active muddy vents - photo 10.2019 Maggie Mooney-Seus / NOAA Fisheries via AP

Bogoslof - active muddy vents - photo 10.2019 Maggie Mooney-Seus / NOAA Fisheries via AP

The fur seal population of northern Alaska has declined sharply in the last three decades, but marine mammals are appearing in increasing numbers in an unlikely place: a tiny island that forms the tip of an undersea volcano active, Bogoslof.

Bogoslof Island vents continue to spew mud, steam, and sulfur dioxide two years after an eruption that sent ash clouds down the trajectory of jet aircraft passing through the Bering Sea. However, female fur seals find the rocky beaches of the remote island conducive to childbirth.

Bogoslof - fur seals, an adult and a group of young seals - photo 10.2019 Maggie Mooney-Seus / NOAA Fisheries
Bogoslof - fur seals, an adult and a group of young seals - photo 10.2019 Maggie Mooney-Seus / NOAA Fisheries

Bogoslof - fur seals, an adult and a group of young seals - photo 10.2019 Maggie Mooney-Seus / NOAA Fisheries

In 2015, biologists estimated the annual growth rate of just over 10% to about 28,000 babies on the island. The 2019 estimate will likely be over 36,000 small seals.
The eruptions of 2016 and 2017 flooded the landscape with rocks and killed all vegetation. They have also changed the morphology of the island.

Food in the near deep waters could be a factor in the behavior of seals. Bogoslof seals eat squid and Northern Smoothtongue, a deep-water fish that looks like smelt, found nearby and therefore reported more quickly to feed young people. Bogoslof is also closer to the winter feeding grounds south of the Aleutian Islands, probably allowing young people to reach the site with less risk in the event of a storm in the Bering Sea.

 

Bogoslof differs from many Aleutian volcanoes. A recent publication in Nature reports giant bubbles with a diameter of 440 meters - a record - spotted by low-frequency hydrophones when emitting a rumbling a few seconds before each eruption.

Sources:
- Anchorage Daily News, with indications from NOAA Fisheries
- AAAS Science - Underwater volcano belched explosive bubbles larger than a stadium

Bogoslof - bubbling fumarole - photo Chris Waythomas / AVO July 2019

Bogoslof - bubbling fumarole - photo Chris Waythomas / AVO July 2019

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