Iceland expects a large volcanic eruption. They don’t know when it will be, but it will be. Since the end of October, the earth has not stopped shaking in the southwest of the island. In that same area there have already been other eruptions, the last one in summer. But this time, with the land opening up for miles, they fear it will be one they will remember.
What is happening?
On October 24, the ground began to shake in the southwestern part of the island. In a country as volcanic as this one, with more than 200 active volcanoes, the fact that the earth shakes does not affect the daily lives of Icelanders. But the number of small earthquakes has continued to increase. They are now produced at a rate of more than 1,000 a day. This is what is known as a seismic swarm: a similar phenomenon, but on a smaller scale (barely a hundred tremors), preceded the eruption on La Palma in September 2021. This is what the authorities fear, that one of the volcanoes in the area will erupt. But it may remain a mere emergence. The volcanologist from the University of Iceland, Ármann Höskuldsson, remembers it: “Most earthquake swarms end with cracks and faults and without an eruption. That said, we know that we are at the beginning of a great tectonic event that is releasing the tectonic tension accumulated over the last 800 years on the peninsula.”
“We are at the beginning of a great tectonic event that is releasing the tectonic tension accumulated over the last 800 years on the peninsula”
Ármann Höskuldsson, volcanologist at the University of Iceland
Where is it being produced?
The epicenter of the earthquakes varies, but they are all occurring in a wide area around the town of Grindavík, in the southwest of the island. It is a small fishing municipality located on the Reykjanes peninsula, just 60 kilometers from Reykjavík, the Icelandic capital. At the beginning of the event, the swarm was concentrated to the west of the affected area, but later moved to the east. Over the weekend, the earthquakes moved again, concentrating south of Grindavík, so far south that if the earth opened at that point, it could lead to an underwater eruption. As for depth, the tremors began occurring at more than five kilometers. But on Thursday they were already at 3.5 kilometers, and in recent days they have been happening at just 800 meters.
What is happening beneath the surface?
The changes in the position of the seismic swarm and the rise of the hypocenter have led those responsible for monitoring its evolution and the Icelandic Meteorological Office (IMO) to determine that a magma intrusion would be occurring. The mass must be enormous, with the entire area on top of it. Bill McGuire, emeritus professor of geophysical and climate hazards at University College London, told the Science Media Center that models suggest that “magma is rising along a 15-kilometre-long fracture and is now so close to the surface like 800 meters or even less.” From space, GPS has detected a rise in the terrain of several centimeters a day in various points in the area.
Where will the magma emerge?
Scientists do not know where the magma will emerge. But the fracture, which has opened from southwest to northeast, is a clue. Most likely, according to IMO, it does so at some point in the crack. Experts relate this event to the nearby Fagradalsfjall volcano, which has been accelerating its activity since 2021 and whose last eruption was in summer. Therefore, there is a possibility that the material ends up emerging at this point. What scientists don’t know is when. In their latest notes, the most they have said from the IMO is that “the probability of a volcanic eruption in the coming days is high”
Will there be a volcanic eruption?
If experts do not know where a mass of molten earth will emerge, even less what type it will be. The alternatives are several. The area is relatively flat and the volcanoes do not have the typical conical shape. In that part of the island, and Fagradalsfjall is a good example, the land opens up with volcanic fissures. In this case, the lava flows from some point in the crack and does not have to be explosive in nature. If it does so far south of the fissure, it would already be in the sea. But an explosive eruption at an uncracked point cannot be ruled out. Professor Höskuldsson recalls that volcanism in Iceland is characterized by basaltic lava. “That means that the eruptions are mild and generate lava flows. Compared to La Palma, the ones we expect will not be as explosive and the lavas will be more fluid and can flow faster than those of La Palma”, he details in an email.
Why are there so many earthquakes and eruptions in Iceland?
The meeting between the North American and Eurasian tectonic plates occurs in the middle of the North Atlantic (something similar also happens in the south, but with other protagonists). In reality it is not a meeting, it is a disagreement: both plates are separating. Along the ocean, from south to north, an enormous fissure has thus opened in the seabed, the mid-Atlantic ridge. Although the gap is at the bottom of the sea, thousands of meters away, it also crosses land. And what is this crack with? With Iceland, which he splits in two.
What impacts can it have?
The authorities have declared a state of alert in Grindavík, but have not yet ordered the evacuation of the city, but of some nearby villages. In the event of an eruption, there is a risk due to toxic fumes, in particular sulfur dioxide. On a global scale, the greatest risk would come from the ejected ash column. Due to the roundness of the Earth, planes from Europe to North America fly far north, which is south of Iceland. An explosive eruption could emit large quantities of particles that complicate air traffic, as did the Eyjafjallajokull, whose eruption kept world aviation in check for months in 2010. But in that case, it was an eruption under the frozen mass and it was the interaction between the lava and the ice that caused the ejection of immense quantities of particles. There is no ice here, but if the eruption were maritime, it would increase the risk.
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The post first appeared on elpais.com