The town of Grindavík in south-west Iceland has been evacuated after hundreds of earthquakes caused by shifting underground magma sparked fears of a full-blown volcanic eruption. Here are some of the key questions and answers about the increase in volcanic activity.
What has been happening and why?
Iceland’s Reykjanes peninsula is being hit by hundreds of earthquakes a day. The earthquake swarms, as seismologists call them, began in late October. Bulges in the land have appeared as magma moves up into the Earth’s crust.
The earthquakes have decreased in frequency in the past couple of days, but the Icelandic Met Office said on Wednesday that the probability of an eruption was still considered high.
That’s because on 10 November a 14.4km (nine-mile) magma-filled crack unexpectedly and suddenly formed between two to five kilometres beneath the peninsular, running from south-west to north-east. Its formation occurred alongside a new cluster of earthquakes.
What precautions have been taken?
The population of Grindavík was evacuated last Friday. “The town has been badly shaken. There’s cracks running through the town, there’s even bits of land that have actually sunk down suddenly by over a metre, there is steam escaping from burst hot water pipes,” said Dr Dave McGarvie, a volcanologist at Lancaster University.
A popular geothermal spa called the Blue Lagoon was closed before the magma-filled crack occurred, and a defensive wall is being built around the Svartsengi geothermal power plant to protect it from potential lava flows.
What would an eruption look like?
Initially a crack would open up on the Earth’s surface and magma would be propelled a couple of hundred metres into the sky, forming a fire fountain.
“The eruption is likely to be ‘effusive’ ie one that creates lava flows, similar to the eruption that occurred on La Palma last year,” said Saskia Goes, professor of geophysics at Imperial College London. “The lava would likely cover an area around the eruption site.” Some of the gases released may be quite toxic, she added.
The greatest potential for damage is in and around Grindavík, where the fissure passes below.
“This is a nightmare scenario. If the magma gets to the surface in that western part of Grindavík, parts of the town will be destroyed by lava,” said McGarvie.
Is a repeat of the 2010 air travel chaos on the cards again?
A repeat is unlikely. That eruption was at the unconnected volcano at Eyjafjallajökul in southern Iceland and involved a sticky type of magma. It shot huge amounts of ash into the atmosphere, forcing the cancellation of 100,000 flights and leaving more than 10 million travellers stranded.
As McGavie points out, the magma seen in recent eruptions on the Reykjanes peninsula is very fluid, meaning bubbles of gas trapped inside can escape instead of breaking the magma apart to form ash, as occurred at Eyjafjallajökul.
Iceland seems to have had a lot of volcanic activity in recent years. Is this the norm?
Situated in the North Atlantic, Iceland straddles the Mid-Atlantic ridge that separates the Eurasian and North American tectonic plates. These huge slabs of rock are moving apart at a rate of a couple of centimetres a year, resulting in seismic and volcanic activity.
The spreading “doesn’t happen equally across the country”, said McGarvie. “Sometimes places won’t spread for several centuries and suddenly that area will spread quite rapidly over a few years.”
Iceland has 32 volcanic systems relating to active volcanoes. Before 2021 there had been no volcanic activity on the Reykjanes peninsula for centuries, leading some experts to consider it could even be volcanically extinct.
Since 2021, however, there have been eruptions every year. These were foreshadowed by an academic study published in 2020 that found that volcanic activity in the peninsula paused for about 800 years before kicking off again for around a century with scattered eruptions.
McGarvie said it was likely that volcanic activity would crop up elsewhere on the peninsula. “There are volcanoes on the east of the peninsula that are likely to become activated if this continues … perhaps threatening other coastal communities,” he said. “That would be the next concern.”
