James Stewart

And terrifyingly, the most recent seismic swarms and eruptions fit the expected cycles uncannily well.

This activity is right on schedule.

But when this cycle last played out, it was medieval communities who were pushed to the brink.

What can modern Icelanders really do in the face of a cycle that cannot be stopped?

Well, they're going head to head with the lava, obviously.

Modern GPS and Interferometric Synthetic Aperture Radar, or INSAR, from satellites show that before eruptions, the land inflates as magma accumulates.

In 2021, some areas rose by tens of centimetres before subsiding again.

Taken together with thousands of small earthquakes, magma pathways can be mapped in real time.

This allows geophysicists to estimate the volume of magma involved as well as the depth and shape of the reservoirs.

And all of this gave Iceland time to plan.

Well, as much planning as you can do when it comes to huge impending lava flows.

When seismic activity first returned to the Reykjanes Peninsula, Iceland's Department of Civil Protection and Emergency Management recognised its significance.

To prepare for the looming period of increased volcanism, they established the Infrastructure Protection Group, which feels like it sort of needs its own Avengers-style superhero fanfare, doesn't it?

The IPG does pretty much what it says on the tin.

This crack team of engineers, scientists and emergency planners work to protect people and critical infrastructure from lava.

As the 2021 eruptions near Fagradoshla unfolded, lava eventually spilled beyond sheltered valleys and began creeping towards roads.

The Department of Civil Protection made a pivotal decision.

They would try and hold it back.

With no recent precedent to draw from, this response became a real-time field experiment in lava flow engineering.

And the first challenge was deceptively simple.