Nature’s symmetry is something we take for granted in flowers, insects and the face of a tiger, for example. In geology, however, it is rarer and its occurrence is something to marvel at. In a Giant’s Causeway, Nature has spectacularly revealed her mathematical genius, producing tens of thousands of multisided columns of rock packed together like a giant-sized handful of hexagonal pencils.
From a distance, this looks like just another part of Country Antrim’s enchanting coast, but suddenly the eye is caught by a strangely chequered promontory. It leads out from the base of the cliffs and descends gently into the sea like a huge, crudely fashioned slipway. For a moment it causes the mind to reel. It looks for all the world like the kind of landscape that is produced by computer graphics for a video game. Yet this extraordinary geological freak has ancestry dating back some 60 million years.
The continents of North America and Europe, which had been joined together, began to split apart. The Atlantic Ocean opened up between them and gradually spread out from a central volcanic rift on the ocean floor. Iceland, with its numerous active volcanoes, stands on the rift today. Lava areas in Ireland and Scotland were produced on the rift as the continents began their slow journey.
40,000 Basalt Columns
As the lava poured forth in Country Antrim it formed the largest lava plateau in Europe. The basalt content of some of the lava was unusually consistent. As it solidified, it contracted, but the forces of contraction were so evenly distributed that it cracked with geometric precision. The same process can be seen when the thick layer of mud in the bottom of a puddle dries in the sun.
On the Giant’s Causeway the basalt columns average 18in (460mm) across and vary from about 3ft to 6ft (1m to 2m) high. The Causeway is about 200yds (180m) across at its widest, extends 170yds (150m) into the sea and consists of some 40,000 columns.
Over the millennia, erosion by glaciers in the Ice Age and relentless battering by the Atlantic has shaped the Giant’s Causeway into the form we see today.
Each column of basalt consists of a series of segments about 14m (360mm) long which have been welded together, but which separate under stress. Now and then exposed sections are sheared off by the waves at the fault line between segments. This has given the causeway its stepped effect.
The Giant’s Causeway is the most famous of the basalt features piece of coastline. But there are many others in the cliffs behind the causeway and neighbouring bays. Over the years they have gained descriptive. Oregon is a group of towering columns embedded in the cliff face of the next bay, Port Noffer. The Amphitheatre is a bay surrounded by extraordinary clusters of columns. Other notable shapes include the Giant’s Pot Lid, the Wishing Chair, the King and his Nobles, and the coffin.