Aldeyarfoss is one of the most beautiful waterfalls in Iceland, found within the north highlands in the Skjálfandafljót river. It stands at twenty metres tall, and plummets into a beautiful blue lagoon. It is best known for its surrounding geology, as on either side of it are rows of hexagonal basalt columns, features found in few places around the world.
These columns are so perfectly formed and symmetrical that they seem to be carved by hand. They can, however, be explained by physics.
When lava was flowing down the cliff faces at Aldeyarfoss during an eruption centuries ago, the outer lava, which was exposed to the air, cooled into solid rock fasting than the layers beneath. In this case, the lava was moving in a way that meant it cooled quickly at the same rate over an even surface.
This caused the lava to contract equally across its surface into cylindrical columns, that cracked into the hexagonal structures due to the different levels of pressure in the rock.
These basalt columns can be found in several places around Iceland, such as along Gerðuberg on the Snæfellsnes Peninsula and at the cliffs in the village of Hofsós. The only other easily accessible waterfall with them, however, is Svartifoss in the Skaftafell Nature Reserve, in the south-eastern corner of the country.
At Aldeyarfoss, the columns are more diverse in colour than their black counterparts at Svartifoss, with yellow and red shades created by the sulfur and iron brought up in the eruption.
