The Giant’s Causeway on the northern coast of Antrim is an example of unexpected symmetry in nature. Its irregular hexagonal black basalt columns appear as the work of stone masons. The causeway itself appears as a mass of more than 32,000 hexagonal (six sided) columns of volcanic rock called basalt. They extend to some 183 metres out to the sea. The columns vary from 15 to 20 inch in diameter with a height upto 9m (20 ft). In places the causeway is 40 ft wide and is highest at its narrowest part. The most remarkable of the cliffs is the Pleaskin, the upper pillars of which are 400 ft high. Do you know how this unexpected symmetry was formed?
There are many versions about the formation of the Giant’s Causeway. One local folklore ascribes its formation to a race of giants, who built it as a roadway to Staffa where a similar structure occurs. According to another legendary story, the local Giant’s Grave was caused by two giants in contest. They stood on a hill and hurled rocks at each other. But the one whose rock fell short was so mortified that he died of vexation—thus irrevocably shaping the landscape.
However the scientific explanation behind its formation is as follows:
Fifty million years ago Antrim was in the heart of a great volcanic region which also embraced the Western Islands of Scotland, Iceland and the east coast of Greenland. In Antrim the sheets of liquid lava spread out over the area and started solidifying as they cooled down. While they were cooling they contracted a little – and so shrinkage fractures formed just as they do in the sun-dried mud of a village pool. The consistency of cooling lava is such that it would tend to form straight shrinkage cracks and, if the pattern of cooling is regular enough, these would form a network of hexagons. As the lava cooled through its depth the hexagonal surface cracks extended downwards and formed the edges of the massive columns visible today. It extends for 5 km. (about 3 miles) and is a great tourist attraction.