Icelandic town evacuated due to concerns about volcanic eruption.

The town of Grindavík on the Reykjanes Peninsula, Iceland, which has about 3000 permanent residents plus a thriving tourism industry, was evacuated on Saturday 11 November 2023, following a sharp increase in Earthquakes in the area, which geologists fear may be linked to an imminent eruption from the nearby Fagradalsfjall Volcano. Iceland, which is an Earthquake-prone country with numerous active volcanic fields, began to suffer an increase in seismic activity on 25 October, since when it has suffered around 22 000 Earthquakes, with the Reykjanes Peninsula being particularly affected. In the 24 hours before the evacuation was ordered, 1400 Earthquakes were reported beneath Iceland, 880 of them beneath the Reykjanes Peninsula.

A crack in a road in the town of Grindavík on the Reykjanes Peninsula, Iceland, caused by an Earthquake this week. Ragnar Visage/RÚV/Reuters.

The evacuations were triggered by the discovery of a magma tunnel running directly beneath the town at a depth of about 1.5 km. This is about 12 km long, originating near Stóra-Skógfell hill, and running beneath the town and some way out to sea. There appears to be a considerable amount of lava in this tunnel, leading to fears that any eruption would be considerably larger than the Vestmannaeyjar eruption of 1973, in which a 3 km long fissure opened, resulting in the destruction of 400 homes, and an ashfall which covered most of Iceland, reaching 5 m deep in places, although only a single person lost their life. 

The length of the magma tunnel and its position partly under the town of Grindavík.  Kristrún Eyjólfsdóttir/RÚV.

Iceland lies directly upon the Mid-Atlantic Ridge, a chain of (mostly) submerged volcanoes running the length of the Atlantic Ocean along which the ocean is splitting apart, with new material forming at the fringes of the North American and European Plates beneath the sea (or, in Iceland, above it). The Atlantic is spreading at an average rate of 25 mm per year, with new seafloor being produced along the rift volcanically, i.e. by basaltic magma erupting from below. The ridge itself takes the form of a chain of volcanic mountains running the length of the ocean, fed by the upwelling of magma beneath the diverging plates. In places this produces volcanic activity above the waves, in the Azores, on Iceland and on Jan Mayen Island. All of this results in considerable Earth-movement beneath Iceland, where Earthquakes are a frequent event.

The passage of the Mid-Atlantic Ridge beneath Iceland. NOAA National Geophysical Data Center.

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