“The volcanic eruption in the Reykjanes region seems inevitable”

  • Iceland is preparing for an impending volcanic eruption on the Reykjanes Peninsula in the southwest, just a few dozen kilometers from the capital Reykjavik.
  • Since Thursday, strong seismic activity has shaken the region and the ground is cracking under the pressure of rising magma. This is not the first episode of this type to hit this peninsula. But this time the magma spreads beneath a city.
  • We take stock with Patrick Allard, volcanologist at the Globe Physical Institute.

In the coming days? During the night ? Even before ? What is certain, says Patrick Allard, a volcanologist at the Paris Institute of Globe Physics (CNRS), “is that a volcanic eruption is now inevitable” on the Reykjanes Peninsula, in southwestern Iceland, just a few dozen kilometers from Reykjavik. the capital.

The region has been experiencing significant seismic activity since late October. The Icelandic Meteorological Institute (IMO) has recorded more than 23,000 earthquakes since October 25, with a sharp acceleration late last week. On the morning of December 8 alone, 800 tremors were recorded. Most importantly, magma accumulates beneath the surface between 5 and 2 km depth, causing the soil to swell and crack. Icelandic authorities took the lead by declaring a state of emergency on Friday, temporarily closing the ‘blue lagoon’, a famous spa, and ordering the evacuation this weekend of Grindavik, a town of 4,000 inhabitants under which the magma flows.

In regular contact with his Icelandic colleagues in recent hours, Patrick Allard deciphers the situation 20 minutes.

What is this volcanic phenomenon currently threatening the Reykjanes Peninsula?

This is a so-called ‘fissionable’ eruption. It is not linked to a volcano, but to a system of fractures in the rock up to the surface, under the pressure of the magma that penetrates into the depths. This is not the first time that such a phenomenon has occurred on this Reykjanes Peninsula. It is even the fourth since 2021. These magma infiltrations are the result of the movement of the “mid-Atlantic” ridge, a large volcanic chain of 15,000 km that crosses the Atlantic Ocean, from north to south, from which the “North -American” and “European” license plates. These movements can cause fissure eruptions.

What do we know about the situation in recent hours?

There are still no results. But the magma is building up, especially since last Thursday, with this strong acceleration of tremors; the strongest measured have a magnitude of 5.2. According to the information we have from Iceland, the seismicity has decreased considerably in the last few hours. There are fewer earthquakes and they are less strong. There have been 900 since midnight, and they are now generally below magnitude 3. The rate of ground deformation has also slowed somewhat.

Yet this zone west of Grindavik is already about fifteen kilometers long, with faults that are sometimes up to a meter deep. Currently, the magma is mainly concentrated between 5 and 2 km from the surface. It remains very close, mainly because the surface rocks are less resistant than those at depth. The magma should break them more easily and cross this final barrier very quickly. The eruption could possibly occur in the coming hours.

Icelandic authorities appear to be taking a more hands-off approach, having allowed certain residents of Grindavik to return last Monday to evacuate valuable items and livestock that could not be saved.

The volcanic eruption seems inevitable today?

It’s hard to say when, but yes, she knows for sure. The previous three episodes had all resulted in pimples. We talked about it less because these phenomena occurred far from inhabited areas. With permission from the authorities, Icelanders and passing tourists even went there to admire the eruptions and the lava rolling down the slopes.

These concerns are much more appropriate this time around. On the one hand, the infiltration of magma under the soil takes place a little further south and runs straight through the center of this port city of Grindavik and ends at sea, on the other hand, this episode is more powerful. The volume of magma is larger, it rises faster and over a greater length. It certainly won’t be gigantic and catastrophic. However, the damage would be significant for Grindavik, an important port in the country. And 4,000 evacuated residents are not nothing in Iceland. That’s 1% of the population. The eruption could also damage other infrastructure in the region.

In addition, there is the possibility of an eruption partly under the sea… Why is this to be feared?

Indeed, more explosive phenomena could occur, caused by the interaction between the magma of about 1200 °C and the cold temperature of the sea water. The fragmentation of the magma will be accentuated and could result in the release of ash columns into the atmosphere. These particles could then fall on an area larger than the Reykjanes Peninsula, including possibly Reykjavik, not that far away. The consequences could then be much more serious, especially in a country like Iceland, where the economy is largely based on agriculture and fishing.

Could this volcanic eruption have consequences far beyond Iceland, such as the 2010 eruption of Eyjafjakkajökull, which led to the largest closure of European airspace in peacetime and the cancellation of 100,000 flights?

A priori no. In 2010 there was a volcanic eruption, 1,500 meters deep and with more viscous magma, richer in gas and therefore more explosive. This promoted the emission of ash columns. This time we are at low altitude and on much more liquid magma, which flows rather than explodes.

But as we just said, the consequences could be greater in the event of an underwater eruption. In this case, the consequences could be greater and could, for example, paralyze Reykjavik airport and perhaps also change the routes of other flights. Without it, it seems to me, global traffic will be as disrupted as the 2010 eruption.

A stable number of volcanic eruptions around the world, but…

“We record between 60 and 100 volcanic eruptions around the world every year,” says Patrick Allard. A range that is neither increasing nor decreasing. At least for now. Melting glaciers due to climate change could increase volcanic activity in some regions. “Mostly in Iceland or along the Andes,” continues the volcanologist from the Institute of Globe Physics in Paris. This melting of ice – some volcanoes were covered by a layer of several kilometers – will reduce pressure on the magmatic systems that feed these volcanoes. This can be seen in volcanic dating and past deposits. In warm periods, when the glaciers melt, we see an increased frequency of outbursts. »

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