A Rock and a Hard Place

Basalt colums descending - Photo by Vikingchild

Back to the Iceland travelogue! The picture above shows the formation of basalt columns at the beach near Reynir, in the south of Iceland (near Vik). These form from lava flow and can be seen in places such as the Giant's Causeway in Ireland and the Devil's Postpile in California

I love the formation of the hexagons. When crystals form, they tend to have a shape that reflects the underlying structure at the atomic scale (the crystal structure). However, in this case, we're talking big and we're talking about geology, and lava, and things that aren't chemically pure. Basalt is far from pure! So the formation of the big hexagons doesn't reflect the underlying symmetry, but the forces of nature. As the lava cools, there is natural shrinkage, which leads to strains and cracking. Nature likes hexagons (see: honeycomb) as hexagons conveniently pack, or tesselate. That's why many tiling patterns - lino, paving - comes as hexagonal. So, cracking of the lava into hexagonal columns is an easy way to relieve the strain whilst minimising gaps. There you go.

It's also nice to look at even if you don't know how it forms! But this reminds me of the story of when Richard Feynman was once told that science makes things dull. Read his response here...