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The rising lava created a crack in the surface of the ground more than four kilometers long in the southwest of the country.
Lava geysers light up the sky with a reddish color. A major volcanic eruption, the fourth in two years, is currently taking place on the Reykjanes Peninsula, located in southwest Iceland. It began Monday, December 18 around 10:45 p.m. local time, following an earthquake that occurred an hour earlier, explains the Icelandic Meteorological Institute on its website.
“Since November, scientists have been closely monitoring volcanic activity in the regionexplain at franceinfo Virginie Pinel, researcher in volcanology at the Institute of Earth Sciences. “GPS and satellite measurements made it possible to observe a succession of earthquakes in the same location and movements of the ground surface in the port of Grindavik, two warning symptoms of an imminent eruption.” As a precaution, the approximately 4,000 inhabitants of Grindavik were evacuated on November 11.
A seismic zone at the junction between two plates
After getting carried away, the various indicators returned to green for the first time: the magma, which was located two kilometers under the ground, ultimately did not reach the surface and the pressure recorded by the scientists fell. But, at the start of the week, researchers detected a new series of very shallow earthquakes. This time, there was indeed an eruption. However, the lava did not flow from the crater of a volcano, but from cracks in the ground.
Iceland, more specifically the Reykjanes Peninsula, is located at the junction between the Eurasian and North American tectonic plates. This is a zone of divergence, called the Mid-Atlantic Ridge. “Concretely, this means that the Atlantic Ocean is expanding and that the eastern part of the island is moving away from the western part by two centimeters per year”, detail to franceinfo the two specialists in vulcanology who manage the GeoTales account on X (formerly Twitter). “This dynamic results in creating cracks and underground movements.”
These cracks are not volcanic in origin. However, Iceland being an important hot spot, the magma takes advantage of these interstices present underground to circulate, create cavities and rise to the surface, if it can no longer advance, then causing new cracks. This type of volcano is difficult to recognize from the ground or space, since it does not have a central crater and its surface is relatively flat.
Lava does not spread into the atmosphere
Under the Reykjanes Peninsula, volcanic activity has resumed very intensely since 2021. The appearance of this eruption therefore did not surprise the authorities and scientists, but its characteristics are of concern. “At the beginning, the lava was extremely liquid, it came out from five points of the fissure at a very high flow rate”, explain the GeoTales account managers. During the last eruption of the Fagradalsfjall volcano in June 2021, the lava flow was 12 m3 per second, compared to 200 m3 this time, the equivalent of an Olympic swimming pool every 12.5 seconds. The crack also expanded rapidly, going from 500 m at 10:45 p.m. to more than 3.5 kilometers a few hours later. It now reaches more than four kilometers.
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Less frequent than those observed in volcano craters, “these fissural eruptions mainly take place on basalt lands”, explains Virginie Pinel. In regions covered with this black rock, resulting from cooled magma, the soil is often less resistant and more prone to cracking. Basalt, which covers 99% of Icelandic land, is characteristic of volcanism occurring at the level of oceanic ridges, as shown by the example of Iceland or Hawaii, where a major volcanic fissure appeared in 2018.
Although impressive, this eruption is not particularly dangerous, because this area scrutinized by volcanologists is hardly densely populated. What’s more“Lava spreads only on the earth’s surface and not in the atmosphere, because the gas concentration is too low to cause an explosion”, details the GeoTales duo. The phenomenon therefore did not cause a halt to air traffic.
Moreover, the volcanic eruption was already losing intensity on Wednesday. “The power of the eruption decreased over time, as did the seismicity and deformation” from the ground, the Icelandic Meteorological Institute wrote on its website on Friday morning.