James Stewart

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.

Where to put a barrier?

And that's where engineers like Horn come in, and thank you so much to her, she helped us massively in researching this video.

With a background in hydrology and hydrodynamics, Horn's expertise was in modelling floods and river ice, both slow and fast-moving destructive flows shaped by gravity and terrain.

Yeah, those fundamental principles, it turned out, could be applied to lava.

By using flood simulation software originally designed by the US Navy, she was able to quickly predict, with remarkable accuracy, where molten rock was most likely to go next.

Teams rushed to build the first experimental barriers using whatever they could find in situ, literally anything, mud, gravel, soil from past eruptions.

Crews worked around the clock and they were close enough to feel the burn from the encroaching lava.

This is serious stuff.

Now the aim here was not to stop the lava outright, but to delay it, restrict it, and essentially buy time.

These early tests show that this approach could actually work, but they also revealed some critical lessons.

Firstly, lava type matters, and it matters a lot.