Iceland is a famously volcanic island, well known for earthquakes and eruptions, but the activity striking the country in recent days is far more intense than many have ever seen.
People in the town of Grindavik on the island’s south west peninsula have been evacuated and are waiting out the hundreds of daily quakes in emergency shelters, leaving their homes and belongings behind as a major volcanic eruption threatens to hit.
But why is Iceland so active right now?
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The island straddles the Mid-Atlantic Ridge, an enormous underwater mountain range formed by the boundary between the Eurasian and North American tectonic plates.
These two plates are continually pulling apart, allowing magma from the Earth’s mantle to escape from the surface, adding to the mountains and pushing them up and out.
‘Iceland as a landmass is actually entirely volcanic,’ says Dr Katie Reeves, a teaching fellow at the University of Warwick.
‘The plates are essentially moving apart in opposite directions, and as they do magma in the Earth’s subsurface rises up to fill the gap.’
Where tectonic plates meet is always a hotbed of seismic activity – but in Iceland’s case, it is one of just two factors.
‘What’s unique about Iceland is not only that it’s on the ridge, but there’s also a mantle plume underneath it,’ adds Dr Reeves.
Mantle plumes, or ‘hot spots’, are seen elsewhere in the world, most famously Hawaii, but Iceland is the only one also on a tectonic boundary – doubling the volcanic activity going on.
‘The mantle plume is essentially really hot rock that’s rising to the surface,’ says Dr Reeves. ‘That compounds the volcanism.’
The two factors combined mean Iceland is home to around 130 volcanoes.
And right now, the mantle plume has formed a nine-mile-long river of magma underneath the Reykjanes Peninsula home to Grindavik. Seismologists fear an eruption could happen soon, sending the magma spewing out the surface as lava.
‘The peninsula doesn’t quite run parallel to the ridge, it’s at an oblique angle, but it’s still influenced by these plates moving apart,’ says Dr Reeves.
‘It had been quiet for the last 800 years or so, but it really awakened in 2021 with the eruption of the Fagradalsfjall volcano.’
That eruption lasted six months.
‘We’ve had three eruptions since then, and what we’re seeing now is the migration of magma beneath the peninsula, which scientists are monitoring,’ she says.
Thor Thordason, professor of volcanology at the University of Iceland, warns an eruption is now imminent, with the magma less than 800m below the surface.
‘Unfortunately, the most likely eruption side appears to be within the boundary of the town of Grindavik,’ he said, speaking to the BBC.
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