Volcanoes are a fascinating subject and this project investigated a key problem: is it possible to predict an eruption in time to warn local communities?  

The short answer as I discovered was - no it isn’t, but it’s a close run thing.  

My first stop was Mount St Helens in Washington State which famously blew apart in the eighties. I’d seen the same news reports as everyone else when it happened but did not appreciate the magnitude of the eruption.  

And that’s the thing about seeing something for yourself. We started getting some indication of the scale of the blast when we were still 16 miles from the volcano.  

25 years after the event – to the day as it happened – the spruce trees still lay flattened into the hill side like a giant palm had pressed them into the ground. We started to imagine the terrifying 600 Deg C blast tearing down the mountainside when Mount St Helen’s erupted, blowing a cubic mile of rock and ash into the air.  

That’s like the surface area of Hyde Park and a mile downwards blasting into the air at a thousand miles per hour in a few seconds.  

We met a park ranger who had seen cars and RVs blasted right over the tops of the hills at the moment the pyroclastic flow smashed into the surrounding dips and valleys.  

Below where he was standing the valley was 200 feet higher than it had been before the eruption, plugged by ash and rock which had been blown there or flowed down as water and ice combined to roar along the course of the river in a lahar. Bear in mind a cubic metre of water weighs a ton before you factor in movement and things like rocks carried along in the flow.  

There were still vehicles and their occupants entombed beneath the new valley floor. They'd either ignored the warnings – and the mile high plume of ash and smoke which belched out for days before the eruption – or had been driving towards the mountain at the time to get a better look.  

In short, it looked like the aftermath of a nuclear explosion and we were humbled by witnessing its terrible effect for ourselves.  

At the observatory we found dozens of scientists being interviewed by the media about the 25th anniversary. Many of them had witnessed the eruption with their own eyes. It was an emotional day and one I’ll never forget.  

I caught up with Don Swanson, the scientist responsible for counting down to the eruption, at the Kilaeau Volcano Observatory in Hawaii. Don managed to charter a heli for the three days before Mount St Helens erupted and took gas and temperature readings by flying low over the mouth of the volcano, which was a big risk in itself.  

When the seismic mini eruptions started to swarm into a continuous boom, he knew something bad was going to happen and he along with the other assembled experts told everyone within 20 miles of the volcano to evacuate. He got me a recording of the sound of an imminent eruption – you can listen to the chilling sound of approaching mayhem here.  

Mount St Helens was and is a very well documented and observed sleeping giant – it’s rebuilding its dome now because material continues to be ejected from the caldera where the top and side of the mountain used to be. The slightest quiver is measured and reported. The real threat are volcanoes like Merapi in Java which are less well monitored and which have a large local population attracted to the farming richness of the volcanic soil.  

What draws people to a permanently dangerous environment from which they have no hope of escape in the event of a sudden eruption is a whole story in itself. And remember if Mount Rainier, visible from the Mount St Helens Observatory, were to erupt under the billions of tons of ice which cover it, Seattle would disappear under the biggest lahar ever witnessed.

To watch video click here.