underwater volcanism

A deep dive between the islands of Luzon (known for its Taal and Pinatubo volcanoes) and Mindoro, in the Passage of Verde island, in the Philippines enabled divers from a group of researchers from the University of Austin in Texas and Dutch scientists to find themselves in an environment of bubbles of carbon dioxide, which they describe as similar to champagne.

This place was named "Soda Springs". As Professor Bayani Cardenas says, the place was discovered by studying how an island's groundwater could affect the ocean environment of the Verde Island Passage, one of the most diverse ecosystems and home to flourishing coral reefs.

As noted, this is not a nightmare linked to climate change, but the bubbling is linked to an underwater volcano (not specified) which evacuates its gases through cracks on the ocean floor, and for decades, or millennia.

The study of this environment with a high CO₂ content - with concentrations reaching 60,000 to 95,000 ppm, or more than 200 times the CO₂ concentration of the atmosphere -, and close to prosperous reefs, must be studied. Carbon dioxide levels drop away from the seeps, but remain high along the coast of the Calumpan Peninsula, in the range of 400 to 600 ppm.

The analysis of the waters also proves that the sources discharge sea water in a variable mixture with water from the water table of the nearby island, and susceptible to pollution.

The study, which also makes it possible to refine the sampling methods in this type of environment, was published in the Geophysical Research Letters under the title "Underwater groundwater and vent releases in a volcanic area associated with the coastal acidification ".

Sources:

- Submarine Groundwater and Vent Discharge in a Volcanic Area Associated With Coastal Acidification. Geophysical Research Letters, 2020; 47 (1) DOI: e10.1029 / 2019GL085730 Texas Geosciences - University of Texas at Austin - link

- Deep Diving Scientists Discover Bubbling CO2 Hotspot - link

A joint study by the German Center for Geoscience Research / GFZ and the Institute for Research in Astrophysics and Planetology, entitled "Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation", examines the seismicity associated with the seismic crisis that started in June 2018.

It highlighted magmatic movements under the seabed, before and during the eruption of this new volcano off the island of Mayotte.

More than 7,000 volcano-tectonic earthquakes and 407 earthquakes of very long period were studied with new techniques adapted to compensate the lack of instrumentalization (before the MAYOBS 1 campaign with the Marion Dufresne).

The first earthquakes responded to the propagation of a magmatic dyke from the depths of the Moho to the surface.

From June, VLP signals, lasting 20-30 minutes and so powerful that they could be recorded a thousand kilometers away, appeared ... while the subsidence of the soil at Mayotte was measured by GNSS.

The study authors interpret this as a sign of the collapse of the large deep magma chamber, more than 3.4 km³ at about 30 km deep, following its emptying.

The eruption could not be noticed at the start, the seabed being 3 km below the surface.

The earthquakes continue, even if we speak less: according to data from the RéNass / National Network for seismic monitoring, January 1 was marked by 7 earthquakes, including one of M 4.8. This January 8, an earthquake of MLv 1.8 was noted.

Sources:

- CNRS - Espace Presse 07.01.2020 - Volcano off Mayotte: seismicity sheds light on the stages of its formation - link

- "Drainage of a deep magma reservoir near Mayotte inferred from seismicity and deformation"
Simone Cesca, Jean Letort, Hoby N. T. Razafindrakoto, Sebastian Heimann, Eleonora Rivalta, Marius P. Isken, Mehdi Nikkhoo, Luigi Passarelli, Gesa M. Petersen, Fabrice Cotton & Torsten Dahm
Nature Geoscience, January 6, 2020

- BRGM - Volcano and earthquakes in Mayotte: monitoring of earthquake-volcanic activity - REVOSIMA - link

- RéNass / National seismic monitoring network - link