GEOLOGICAL HIGHLIGHTS - Hutton's Unconformity

"No vestige of a beginning, no prospect of an end…." This was how James Hutton, the father of modern geology, viewed geological time and hence the age of the Earth. This eminent Scottish geologist helped to establish the principle of Uniformitariansim in his classic piece of work Theory of the Earth published in 1875.

The idea of Uniformitarianism extends from the observation that the gradual Earth processes at work in the present have also operated in the past. For this to hold true the timescale needed to account for the sheer amount of complexity and change that can be charted throughout Earth history must be very grand indeed.

It was on Arran, and other localities in Scotland, that Hutton first found proof for his idea of immense geological time. Near Lochranza on the north shore of the island, almost vertical Dalradian schists are seen to be unconformably overlain by sandstones and cornstones of Carboniferous age. Hutton understood that the two rock units meet at a discordant angle and that the schists were originally sediments that had been buried to great depths before being exhumed and overlain by the sandstone. He then concluded that it must have taken an almost unimaginable period of time for this to occur. The unconformity extends from the mouth of a small stream, the Allt Beithe, southwestwards along the coast for about 100m (NR 936521). This locality is very important to the history of geology and must be treated with due respect; please do not hammer!