James Stewart

A'a lava is chunky and rough.

When this hit a barrier, it thickened and piled up like a geological porridge.

So if you want to stop it, your walls need to be built like a medieval fortress.

Pahoehoe lava, on the other hand, is smooth and much runnier, behaving more like honey, if we're doing the breakfast metaphor thing.

Interestingly, drone surveys showed that it flowed over dams, but could be redirected using angled burns.

And it was this piece of information that immediately suggested that a barrier doesn't have to stop lava flow, it just needs to guide it.

These initial field trials made up as they were going along led to the most ambitious lava defence project ever attempted.

And as volcanic activity shifted further west, closer to towns, the lessons became more critical.

Multi-kilometre barriers up to 24 metres high have now been built across the Requienes Peninsula.

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.