The arrival of the lava from the La Palma volcano to the sea is a bomb. Not only because of the explosions generated by the hydrothermal and chemical reaction, but also because it will drastically alter the conditions of the coastline. However, this effect will be transitory. Scientific studies on similar phenomena reflect a greater and faster regeneration capacity of the marine environment after the accumulation of lava. Some research has recorded normal levels two years after the episode. An expedition of the Spanish Oceanographic Institute (IOE), according to Tomás Vázquez, marine geologist of this entity, studies, in addition to the geological effects, the physical, chemical and biological consequences of the eruption on the coast.
- The delay in the arrival of the lava to the sea increases the destruction capacity of the volcano on land
The first reaction was thermal. Tons of rock with temperatures above 1. 000 degrees are immersed in water with a medium temperature of 23 degrees. The second reaction, immediate, is chemical, between the components of the lava at extreme temperatures with the water and the salts of the sea, formed by sodium chloride. Raúl Pérez, geologist, seismologist and researcher at the Spanish Geological Mining Institute (IGME), who is part of the monitoring team for the Cabeza de Vaca eruption on La Palma, explains: “A spectacular column of steam is formed, but you can produce collapses by accumulation in the front, and interactions with water can produce explosions. It is not a chocolate fountain on water. We must also be attentive if a fissure opens and finds a body of water in its path, as it can lead to a hydromagmatic interaction. ”
To know the long-term consequences that will have the arrival of lava to the sea there are investigations carried out on similar episodes. The closest is the one developed by the IEO on the underwater eruption near the neighboring island of El Hierro since October 2010 until March of 2011, when it was considered completed.
Like all volcanoes , an expulsion of a large amount of magmatic material and gases was generated. But Tomás Vázquez clarifies that, in the El Hierro eruption, the interaction with the water was immediate “and, in the case of La Palma, it is not directly deeper at the bottom, but much more superficial”
Water conditions also change substantially, with increases in water temperature and acidity due to emissions of carbon dioxide, carbonic acid and sulfuric acid. The IOE geologist clarifies that, in the case of El Hierro, this alteration in the sea was very significant because “all the gas emissions were underwater.”
The concentrations of metals such as iron, copper, cadmium or mercury, as well as an increase in carbon dioxide emissions and a decrease in oxygen that, in the case of El Hierro, became almost total in some measurements. However, these reactions will not reflect the same levels on La Palma, where the mouth will be on the coast. According to Mario Lebrato, from the Institute of Geosciences at the University of Kiel (Germany), “these fluids do not react as in deep water systems.”
The alteration of the environment also generates the temporary flight of species with movement capacity, until the recovery of normal levels, and the death of specimens by the collapse generated by the acidity of the water and the increase in temperature
The El Hierro study revealed “different responses in marine organisms ”. Both the study of this eruption and other similar ones reflect the proliferation of phytoplankton (photosynthesizing microorganisms that live dispersed in water) that take advantage of the increase in nutrients and are able to survive at high temperatures and concentrations of metals.
Samuel Wilson, who published a study in Science on the effects of the lava from Hawaii’s Kilauea volcano in the summer of 2018, highlights that it generated an enormous proliferation of phytoplankton in nearby waters, which persisted for the two-month duration of the volcano’s eruption and quickly dissipated when the lava stopped flowing. The cause, according to the researcher, was the presence of “unexpectedly high concentrations of nitrate and the increase in temperature.”
On the contrary, the alteration of the environment also generates the temporary flight of species with movement capacity, until recovery of normal levels, and the death of specimens due to the collapse generated by the acidity of the water. Tomás Vázquez adds that “the temporary increase in temperature is very harmful for species accustomed to a very specific range of temperatures and that live in the sheet of water.” “Some try to flee even before the lava arrives, as soon as they begin to detect that the water temperature is changing.”
In the studies of the Bioecomac research team (Biodiversity, Marine Ecology and Conservation) on the eruption of El Hierro detected ash sediments and substances derived from sulfur that end up being displaced by tides and storms, the appearance of new organisms, transitory changes in the dominant species of algae and increases of mollusks and invertebrates whose larvae survive to temporary changes and benefit from less predatory pressure from fish that move away or die. When sea conditions allow it, the fish return and take advantage of the increased planktonic production.
It will be easier for planktonic organisms to re-colonize the environment
Tomás Vázquez, geologist at the Oceanographic Institute Spanish
The geologist of the Oceanographic Institute adds that “it will also be necessary to see how it affects the benthos [los organismos que habitan el fondo de los ecosistemas acuáticos], which always takes a little longer to repopulate, but for planktonic organisms, it will be easier to re-colonize the environment.”
The Bioecomac group proposed a biological stop in the El Hierro area to promote recovery. Tomás Vázquez believes that on La Palma “it could also be advisable for the regeneration of fauna and until levels return to normal.”
Recovery times are uncertain, but optimistic. A study over 10 years on an area affected by a volcano and published in Scientific Reports concludes that “catastrophic changes in the morphology of the seabed, the chemistry water, degassing activity and benthic ecology profoundly reshape biogeochemical processes over a year to levels not observed before. However, the changes are temporary in nature, with a possible recovery of the system within two years. ”
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