• Question: In places like Fingal's Cave and the Giant's Causeway, I know it is caused by ancient volcanic eruptions but what made it make hexagonal prisms, cubes etc?

    Asked by bleddy to Angela, Gabriele, Karen, Maria, Shane on 18 Nov 2013.
    • Photo: Gabriele De Chiara

      Gabriele De Chiara answered on 18 Nov 2013:

      Imagine the boiling lava that is cooling down. By convection the cold part will flow down and the hot part will flow up. So there will be columns of lava going up and down. Because of the high pressure these columns will be hexagonal, why? Think of a bunch of spherical balloons, and try to compress them so they fit in a box. If you notice the arrangement the minimise the space will be when each balloon has 6 other balloons around it. And they shape the get, because of the pushing, is hexagonal! Then because of the closeness to the sea, the lava cooled down very quickly but the structure remained. If you look closely there are also polygons with 4,5,7 and 8 sides. The giant’s causeway is one of my favourite trip in Northern Ireland. I’ve been there 6 or 7 times every time some friend or family comes to visit from Italy!

    • Photo: Angela Stevenson

      Angela Stevenson answered on 18 Nov 2013:

      Excellent question beddy! Hot lava flow cools rapidly, there are contractions which result in the formation of cool columns shaped geological features, like the ones you ve mentioned here. The column’s size depends on the rate of cooling…. most of the time hexagonal shapes are formed but other shapes with varying sides can also be found. It’s hard to believe that these columns are formed by nature! Hope that helps 🙂

    • Photo: Shane Mc Guinness

      Shane Mc Guinness answered on 18 Nov 2013:

      Great answers! And there’s another much more common example of how useful this structure is! Bee hives! Think about the hexagonal structure of the honeycombs in these. Because it’s a lot of effort to produce the wax and build the honeycomb, they have to make sure they’re doing it as efficiently as possible. It’s actually based on some really complicated maths which shows that joining four points laid out in a square is most efficient with two dots in the middle and five lines joining them. When you repeat this many times side by side, you get hexagons!
      Also what about the eyes of flies…..!?