James Stewart

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The Norse Vikings first settled in Iceland in 874 AD, and lucky for us in this instance, were impeccable record keepers.

Their annals and sagas describe fire coming out of the sea and darkness during daytime in the Reykjanes area between 1210 and 1240.

During this period, now often referred to as the Reykjanes fires, the peninsula was gripped by repeated fissure eruptions.

Widespread environmental destruction led to devastating effects on livestock and farming, pushing the medieval communities here to the very edge of survival.

Eight centuries later, what was once recorded as folklore had become a critical guide for modern science and potentially survival.

Beneath soil and lake sediment in volcanic regions are layers of volcanic ash.

When analysed, these tiny shards of essentially glass carry a chemical fingerprint with a precise mix of silica, iron, magnesium, calcium and sodium.

Now, crucially, these fingerprints vary from one volcanic system to the next.

When paired with radiocarbon dating of the sediments above and below the ash layers, as well as observations from old lava flows, the timing and sequence of historical eruptions can be pieced back together.

In March 2020, Christian Sirmutsen from the Icelandic Geo Survey and his colleagues published evidence of at least three major rifting and eruptive episodes over the last 4,000 years, each lasting a few hundred years and spaced roughly 800 to 1,000 years apart.

Now, to be honest, this would have been quite good to know before Iceland set up the majority of its economy, infrastructure and housing in this area.

But even so, what on earth was causing them?

The timing of all these cycles comes back to that uniquely Icelandic geological boiling pot that we talked about at the start.

Yes, Iceland as a nation sits on the Mid-Atlantic Ridge, but the Reykjanes Peninsula in particular sits directly astride it.

There is no single centralised volcano here.

The plate boundary itself is the volcano.

As the North American aneurysm plates slowly pull apart, lateral strain builds within the crust.

It stretches and over time fractures.

This creates underground networks of fissures that are invisible to us at the surface.