On our trip to Iceland this January, we got to see a new perspective on a subject we’ve had earlier experiences with — lava tubes. Formed when lava flows crusted over and subsequently drained, we’ve walked through some in Hawaii — but never previously seen one in a colder clime.
So this is what happens near the Arctic Circle where there’s a lava tube “skylight” (localized collapse of the tube’s ceiling). At this particular point, the outside surface level is about 20′ above the trail along the bottom of the lava tube. So you could hop into the lava tube from this skylight, but you wouldn’t get back out again without ropes.
If you’re curious, I made this photograph in the Raufarhólshellir lava tube, a nice day trip from Reykjavik, Iceland.