Giant’s Causeway (Part 1): An introduction

Dr Trevor Watts (UK) This is the first of two articles on the volcanicity of the Giant’s Causeway and the surrounding area. The Causeway itself is an area of basalt columns, about 100m or so across, jutting into the Irish Sea. A remnant of a vast ancient lava flow, it is located in a coastal strip that is lavishly scattered with other superb volcanic features. The whole area is both beautiful and fascinating, and neither spoilt in any way, nor over-crowded out of season. We (my wife Chris and I) went there because I had a few days’ work in Northern Ireland and it seemed like a good idea to combine this with a short break during an October, half-term school holiday. Fig. 1. The Giant’s Causeway, battered by curling waves, becomes a sunlit wonderland in the evening light of autumn. The geology of the Giant’s Causeway The long-held theory that the Causeway was created by an Irish giant called Finn MacCool in Middle Earth times has – sadly – been discredited. Around 60mya (in early Tertiary times), great masses of molten rock were rising from the depth of the earth’s mantle, probably centred beneath present-day Greenland. These nation-sized ‘lava-lamps’ are collectively considered to be a ‘hot spot’, now known as the ‘Iceland Plume’. They split the earth-wide continent of Pangaea apart in great cracks that were aligned roughly northwest to southeast. This was sufficient to split the land apart on a vast scale, beginning the opening of the Atlantic … Read More

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