Iceland is in a state of emergency. A series of earthquakes that have occurred in recent weeks near the fishing town of Gindavík, just 50 kilometers from the capital, Reykjavík, have put local authorities on notice, who, faced with the prospect of a possible large volcanic eruption, have ordered the preventive evacuation of the area. The Icelandic Meteorological Organization (IMO) is monitoring the situation in real time under the hypothesis of an imminent eruption.
The country is used to volcanic eruptions, but it has been 50 years since any caused the complete evacuation of such a large population. The region experiences, on average, an eruption every five years, although Fagradalsfjall, the volcanic system in the area currently in focus, has erupted each of the last three years. We explain what is special about Iceland and what is hidden behind its imminent activity.
Iceland has 34 volcanic systems that have been active during the Holocene, in the last 11,500 years, according to the official catalog of the IMO, the University of Iceland and the Civil Protection Department of the local police. “It is a completely volcanic island, it is all volcanoes,” says Rubén López, volcanologist at the National Geographic Institute (IGN), in conversation with La Vanguardia. In the last 50 years, more than 20 eruptions have occurred in the country.
The country is located in an area that combines two particularities that make it especially predisposed to volcanism, according to the British Met Office. On the one hand, it is located on the Mid-Atlantic Ridge, an area in which the Eurasian and North American tectonic plates separate a few centimeters each year. This separation causes fissures, that is, the rupture of the Earth's crust, through which magma rises, producing volcanic eruptions.
In addition, it is believed that the island is above a mantle plume, an area in which the magma has a higher temperature than usual. So much so that it melts and thins the Earth's crust. This leads to higher volcanism, which would help explain the frequency of eruptions in the country.
The island combines special geological and climatological conditions, which make it have an unusual volcanic diversity, as stated in a summary article from 2007. Virtually all types of volcanoes and eruptions known on Earth have been recorded. Iceland is home to polygenetic volcanoes, formed over many eruptions, and monogenetic ones, the result of a single event. There are flatter and more vertical ones, formed by the accumulation of lava and layers of ash, and which appear on the ground of the island, but also under water (underwater) and under frozen areas (subglacial).
In Iceland there are effusive eruptions - in which lava is basically emitted -, explosive eruptions - in which tephra, solidified fragments of magma are mainly produced - and a mixture of both. And, throughout history, there have been very intense ones and weaker ones.
The forecast is that the eruption will be effusive and that little ash will be emitted. Therefore, no major effects on air traffic are expected beyond some local impact depending on how the wind blows, explains Lancaster University volcanologist Dave McGarvie to the Science Media Centre. Even so, it is possible that the magma encounters underground water deposits or that the eruption is underwater, situations in which larger quantities of ash could be released.
The evacuation of Gindavík has been a consequence of the proximity of the population to the area where the eruption is expected, rather than due to a possible explosive nature of the phenomenon. However, the IMO has measured ground deformations of up to one meter, something unprecedented in the area, which suggests a magmatic movement greater than that which has occurred in previous eruptions on the Reykjanes Peninsula.
The area where seismicity and ground deformations that suggest an imminent eruption are occurring is the Reykjanes Peninsula, southwest of Iceland. In this region is the Fagradalsfjall system, which has given rise to the latest eruptions on the island, along with five other volcanic systems. “The magma is looking for a way to come out,” explains the IGN volcanologist, “it doesn't have to look for a volcano, but rather it will try to break the ground,” if an eruption ends up occurring.
One of the areas where the eruption could occur is, precisely, the population of Gindavík, which has forced the town to evacuate. There is also the possibility that it could move further southwest, to the Reykjanes volcanic system, and even end up erupting into the ocean.
The authorities have assured that there is “a significant probability of an eruption in the coming days”, but they have not been able to specify their forecast further. In fact, it is even possible that the event ends without any eruption. If it occurred, the event would most likely last from weeks to months, the most common, according to the IMO, in effusive volcanoes. The events that have occurred annually in Fagradalsfjall since 2021 have not exceeded half a year.
“The volcanic origin is very different,” describes the IGN volcanologist. "Iceland is in a ridge, an area where the plates separate and magma shoots upward, while the Canary Islands is an area called a hot spot, and magmatic intrusions come from there." Furthermore, "in Iceland there are many fissures with eruptions with very little gas, which is why the Icelandic eruptions are very low intensity", while the Canary Islands, such as the one in La Palma, tend to be more explosive, continues the expert. “The lava is similar, it is a very basaltic lava, very black,” he concludes.
The variable that provides information about the magnitude of an eruption is the explosive activity index. “It is measured by several factors, such as the ash column, the duration of the volcano, the magma that is ejected…” says López. From there "a fairly complex analysis is carried out, sometimes quite subjective, and it is valued from 0 to 8 on an exponential scale." The volcanologist describes that the eruptions seen in recent years in Iceland tend to be monogenetic, with low explosive activity rates.
