In Iceland, tours head inside a giant tunnel cave carved out after a volcanic explosion.
Darkness inside Vidgelmir
“If you can see your hands in front of you, then I have bad news,” says the guide. “You are crazy.” We’re about 500 metres inside Vidgelmir, a long tunnel-like cave dug into the barren landscape of western Iceland. The lights have been turned out, and it is pitch black. You’d not want to hide away in here without a good torch and a plentiful supply of batteries.
And, for that matter, a big coat. The wind howling in from outside keeps the temperature at about freezing point. At one point, however, it would have been considerably warmer down here.
Vidgelmir was formed by lava. Around 1,100 years ago it poured down from a volcano now covered by the Langjökull glacier.
The creation of Iceland’s giant lava cave
The initial flow was smooth, relatively slow and relatively slow to cool – which in volcanologists’ terminology made it “pahoehoe” lava. And pahoehoe lava has a tendency to create tubes around it as gravity takes its course and makes it flow down hillsides.
The mile-long cave we’re in was essentially the lava stream, and parts of it are weirdly smooth. The walls look more like the mildly rippled chocolate coating on a Mars bar than rock. A less charitable interpretation would be that it’s the result of, erm, a loose stomach. The brown, gloopy look is not entirely appealing, but it’s a result of the lower melting point – it remains as a liquid longer than the faster flowing, thicker lava.
It is mixed up with the occasional streaks of red, green and yellow from iron, chloride and sulphur present during the eruption.
The chocolate coating inside Vidgelmir
But the bigger puzzle is the massive chunks of rock all over the cave floor. These all seem to have a similar chocolate coating – but only on one side.
The answer is that, at some point, they have fallen off the walls and ceiling, leaving the more conventional basalt rockface uncovered. And once this dawns, a few fairly obvious worries about being crushed by humungous breakaway boulders kick in.
Is Iceland’s lava cave dangerous?
The dangerous period, however, is over. Most of the tumult would have occurred in the first few years after the cave was formed. The rocks are still technically cooling after hundreds of years, but for a couple of decades following the eruption, they would have been properly hot. During the cooling process, they would have solidified and shrunk slightly, leading to cracks. Those cracks would destabilise the chunks that broke off. Now, however, enough time has passed for everything to remain fairly safe and solid.
But that’s not to say it couldn’t happen all over again, though. On our way back into the open air, and the bleak, moss-covered landscape, the guide lets us know that the volcano is still active. “So if you start to feel very warm all of a sudden, let me know.”
Booking the lava cave tour
Tours of Vidgelmir are available through The Cave. Advance bookings online are recommended.
More Iceland travel
Other Iceland travel articles on Planet Whitley include a review of the Inside the Glacier tour.
For a big range of Iceland tours, activities and experience, look through the options here.
