The ground beneath Iceland is shaking. Is there a rash on the way?

For the past eight hundred years he has been on the picturesque Reykjanes Peninsula in the far southwest of Iceland, relatively calm You know. But something happened over a year ago. What started out as a low rumble has since evolved into a spectacular series of vibes that peaked over the past week. 17,000 earthquake.

Scientists have since observed part of the Reykjanes landscape change shape and recorded the seismic signature of the flow of magma pushed to the surface. The question that occupies everyone now is whether a rash is imminent.

A few days ago, the answer seemed to be a resounding “yes”. The most plausible scenario would involve spectacular lava fountains and rivers of molten rock, which would not, however, endanger urban centers. Such an eruption would also not pose a problem for passenger planes crossing the skies over the area, as was the case in 2010, when the Eyjafjallajökull volcano erupted elsewhere on the island.

But Reykjanes’ volcanic system is now behaving in surprising ways, so it’s hard to predict whether an eruption will follow in the days or weeks to come. “People are starting to wonder what’s going on there,” says Dave McGarvie, volcanologist at Lancaster University in England.

Past volcanic cycles in this region suggest that recent tectonic disturbances could be the starting signal for a succession of eruptions that can last up to a century. In this case, the Reykjanes Peninsula would be illuminated by the glow of thousands of tiny lava fountains, which would erupt here and there over a lifetime, sometimes disappearing and then igniting again.

For non-residents this uncertainty may be of concern, but for Icelanders this type of geological activity is nothing special. “You live in a very volcanic country, and this is something that people here are learning to live with,” says Thorbjörg Ágústsdóttir, seismologe van Iceland GeoSurvey.

Ascending Magma

The Reykjanes Peninsula, over 17 miles southwest of the capital, Reykjavik, is volcanic like the rest of Iceland and is closely watched. On March 3, seismometers recorded acoustic signals associated with this magma which is pushed through the earth’s crust towards the surface. Signals were coming from around Table Mountain Fagradalsfjall and the volcanoes system Krýsuvík-Trölladyngja, a series of volcanic cracks that cross the peninsula. The ground itself also began to warp, confirming the underground movement of the molten rock.

Volcanologists and authorities feared an impending eruption. “It sounds like the turbulence you would expect as an eruption approaches,” said Kristín Jónsdóttir of the Iceland Met Office (IMO). to local media. Rising magma indicated that an eruption could occur within hours.

“As is the case with other volcanoes across the country, these types of signals are heralding the release of the lava flows,” says McGarvie. But nothing happened.

“It was strange. We weren’t expecting that, ”McGarvie says. “But there are always surprises. You can’t predict anything.

The vibrations that indicate the underground movement of magma have now subsided. They may come back, but they may also have come to a complete stop. “We’ll just have to wait and see what happens,” said Bergrún Arna Óladóttir, IMO volcanologist. “We are preparing for the worst and hope it won’t be too bad.”

When the magma is pushed to the surface through cracks underground, as in this case, there is always a chance that the molten rock will get stuck somewhere and then cool and solidify. The rock then simply remains underground, explains Ágústsdóttir.

“The most plausible scenario, I think, is that this movement gradually decreases and then stops,” says Sigurjón Jónsson, a geophysicist at King Abdullah University of Science and Technology in Thuwal, Saudi Arabia.

The problem is, every volcano is different. Several volcanoes can give the same signals when they are about to erupt, but that does not mean that all volcanoes give similar warnings. The last major eruption on the Reykjanes Peninsula occurred eight centuries ago, shortly after the first humans settled in Iceland. At the time, the science of volcanology did not exist, and without accurate data on this region, no one can say how the volcanoes in this part of the island will behave when they are about to erupt.

However, a closer look at what we know of Iceland’s geological past provides clues to this recent round of earthquakes and may provide a glimpse of what the future holds.

Constantly separated

After a series of heavy eruptions from the 10th to the 13th century it remained fairly quiet in Reykjanes. This changed at the end of 2019, when there was on the peninsula increasingly strong earthquakes were recorded. In February of this year, the region was hit by an earthquake with a magnitude 5.7 and a whole swarm of lighter earthquakes followed last week.

“This is the most intense series of earthquakes in this region for almost a century,” says Jónsson.

The reason for this tectonic turmoil is the fact that Iceland sits on the northern part of the Mid-Atlantic Ridge, a crack in the ocean floor that covers the entire planet. Lava is constantly gushing up along the ridge, which immediately cools, creating new oceanic crust on both sides of the ridge. As a result, the North American and Eurasian plates, which lie on either side of the North Mid-Atlantic Ridge, are spreading apart at the rate our fingernails grow.

Most of the Mid-Atlantic Ridge is submerged, but the Reykjanes Peninsula sits just on the northern part of the Ridge and is regularly separated there. For reasons that are not clear, the fault begins to move once every eight hundred years, causing the number of earthquakes to skyrocket, as it does today. Geologists who have studied ancient lava flows and historians who have scoured the records of the island’s first settlers have concluded that an increase in the number of earthquakes in this region is usually followed by the release of magma.

“We do not yet fully understand why such periods of turbulence with numerous earthquakes occur, but they are accompanied by an increase in magna in the earth’s crust. The interrelation is clear, ”says McGarvie.

As the peninsula separates, new cracks could form in the earth’s crust, which could allow magma to rise to the surface, but experts are not sure this is the case. It is clear, however, that in three of these troubled episodes in the past, a pattern of subsequent tremors and rashes has occurred each time. According to McGarvie, this is now “the last episode.”