James Stewart

Such is the scale of them that two new quarries have been opened to provide enough material.

The new barriers are built with compacted basalt gravel to resist heat and pressure, and they're armoured with boulders and stabilised to prevent erosion and collapse.

They're carefully shaped too, based on lava modelling to steer lava away from towns, key roads, and crucially, the Svart-Svengi geothermal power station.

Of course, there are gaps in these barriers too.

Strategic openings for roads, pre-cast concrete bridges for pipelines and emergency access.

But each one also comes with pre-positioned earthworks in place so they can be sealed within hours if necessary.

And trust me, it's been necessary.

Behind the scenes, the IPG works in constant coordination with the Department of Civil Protection and Emergency Management and Universities.

For engineers like Horn, being on call is the new normal.

As seismic swarms propagate, she can have as little as 50 minutes warning before lava reaches the surface.

In that time, she has to rush to her office, be there to receive the first data, which she uses to model the flow, and then she has to tell the team on the ground which gaps to close off.

After the immediate threat is over, so follows more modelling, more barriers and more refinement, and so on and so on, again and again and again.

But the good news is, so far, these models have been incredibly accurate.

Each time Horn and her team have built new barriers or increased the height of current ones, they've very quickly been needed.

But that job does come with tough decisions.

They can't save everything.

In late 2024, lava overran the car park of the famous Blue Lagoon Spa.

This wasn't a failure of defences, but a reminder of priorities.

Newly installed barriers were designed to protect the power station and the spa buildings.

And the car parks?