Inside an Icelandic volcano

Árni B Stefánsson’s voice echoed out of the shadows, the sound bouncing loudly off the rocky walls. Despite having just been lowered 120m into the magma chamber of Thrihnukagigur, a volcano 30 minutes from capital Reykjavík, his dry tones greeted us as calmly as if we’d arrived in his front room.

It was midsummer’s eve 1974 when Árni was first lowered into Thrihnukagigur’s unknown depths on a rope held by ten of his friends. Not knowing if he’d choke on lingering carbon dioxide, they’d agreed on a simple ‘three tugs if you’re alive’ signal for him to send up when he reached the bottom. Once there, he had just ten minutes to explore by headtorch before being dragged back up and out into the midnight sun.

A doctor by profession, Árni is also a mountaineer and Iceland’s most respected speleologist (a person who scientifically studies caves) in his free time. After 17 further descents to survey the chamber, eight years of serious planning, four powerful halogen lamps and one cablelift rigged up over the cavern mouth, Árni made sure my own descent – exactly 38 years after his first – was considerably easier than his.

Reykjavík’s deserted Blue Mountain ski resort seemed out-of-place in the eerie brightness of the midsummer evening. However, Bjorn Ólafsson (Everest summiteer, and one of the men that originally held Árni’s rope) fitted the surroundings perfectly. He cut a curiously epic figure as he lead us on the 45-minute tramp to Base Camp – across the craggy basalt outcrops and pillowy thick moss of the lava field, and over the rift where Europe and America divide.

This is the first year visitors have been able to enter Thrihnukagigur, so Base Camp is a temporary affair: a portacabin 50m from the summit and six discretely placed portaloos. As we were given a brief lesson on Iceland’s geological history, a thrill of anticipation spread through me – as warming as the two bowls of the kjötsúpa (Icelandic meat soup); I was eager to don a hard hat and scramble into my safety harness. From there, boot-prints and a flag-marked path led us to the summit.

The entrance to the chamber wasn’t much bigger than a couple of double beds, and no more remarkable than any other cavern on the lava field. Except, of course, for the lift rigged across it – the kind you’d expect to see cleaning the windows of a skyscraper. My harness was clipped to the rail of the short bridge across the void; Bjorn then transferred me safely to the lift’s rail before I clambered down into it.

It takes about five minutes to descend the 120m to the floor of the cavern. The quick way down (falling) takes about 4.5 seconds – just enough time, according to Árni, to remember your sins but not enough to repent them.

Bjorn pushed and held the big red ‘down’ button. There was a low metallic screech as the cables limbered up; it settled into a steady mechanic purr, and the lift started slowly creeping down the wall of the opening, tyres rolling across the rocks’ surface to protect it. Gradually, the cavern widened and we began descending through empty space. Suddenly, the lift bounced and lurched to a halt. There were muffled screams. “Sorry,” apologised Bjorn, “it’s a long way down, my wrist gets tired.”

The sky was a bright slit somewhere above us; down below, four halogen lamps marked the edge of the landing site. Everything in between was lost in the darkness.

You could fit the Statue of Liberty and then some into the bottle-shaped cavity. The uneven floor of the chamber slopes down on all sides, disappearing into the dark depths of the earth. As Árni welcomed us, in his calm, echoing tones, a hush fell over us as we tried to take in the scale of our surroundings.

Iron oxides and silicates have stained the chamber walls an underworldly rainbow, from fiery reds and oranges through to dark, purplish blues. You can trace a burnt black line back up to the light where magma once scorched through the fissure: Thrihnukagigur last erupted 4,000 years ago.The only fire left now, though, is in Árni’s speleological passion.

“There is nothing like this in the world,” he told me. “At first I saw no beauty: well, it was dark! Then I saw beauty in the size, then finally I saw beauty in the colours. It’s a strange place. And if you think, fewer people have been into this ‘inner’ space than into outer space.”

It was a sobering thought. I’d been excited about going inside a volcano without any deep consideration of what that might mean. ‘Strange’ is right, but alien is closer; it’s an indescribable feeling, being where humans were never meant to be.

Now that Thrihnukagigur’s chamber of secrets has been found (and in a popular County Park only 20km from the capital), the only responsible thing to do is protect it by regulating human contact. There have been six near misses already. One family unwittingly had a winter picnic on top of the volcano’s frozen entrance, little realising they were just 4.5 seconds from eternity.

The big question, and the reason for summer 2012’s brief trial, is how to go about letting people visit safely while protecting the chamber from erosion. The rough-and-ready cablelift that drew us slowly back up into the clear midnight sun isn’t really a sustainable option as, for example, if an unwary person on the surface dropped something or an earthquake hit, chances are that anyone inside the volcano would be a goner.

The team have developed plans for a tunnel and a staircase into the abyss, but the ultimate future of Thrihnukagigur will depend on careful consideration of the feedback from this summer’s limited visitors. One thing is abundantly clear: Árni is taking a protective, guardian stance over his speleological and spiritual home.

“We are intruders,” he says. “I want people to experience their own smallness and leave a better person than when they came. It’s the fate of tourism to destroy everything it seeks, and I won’t accept that. We must preserve it; it’s a very special place.”

Getting there: Iceland Express is Iceland’s low-fare airline. It flies six times a week from London Gatwick to Reykjavík. Prices start from £89 one way; flight time is three hours.

Getting in: Inside the Volcano runs trips inside the volcano June-August only; 2013 dates TBC. The trip takes 5-6hrs (1hr inside the volcano) and costs ISK37,000 (£197).