Rock of ages
25 April, 2013
As part of Scotland’s Year of Natural, Stirling Castle ran special tours last weekend in support of John Muir Day. This was a 175th-anniversary celebration of Scots-born naturalist Muir (1838–1914), whose work helped preserve some of America’s most stunning wildernesses.
This week my theme is another great Scot, who is closely linked with many Historic Scotland properties. James Hutton (1726–97) is known as the father of modern geology. He was a leading figure of the Scottish Enlightenment, an 18th-century golden age of intellectual and scientific achievements centred on Edinburgh. Hutton is internationally regarded as the founder of geology as a science.
Holyrood Park has two sites directly associated with him: Hutton’s Rock and Hutton’s Section. Both sites are world famous within the geological community and are regularly visited by geologists from all over the world.
Hutton’s Rock, located in the quarries of Salisbury Crags, was identified by Hutton as an interesting example of a vein of iron ore and he persuaded the quarrymen to leave it. One of the first examples of conservation!
Hutton’s Section illustrates the process of rock creation, both by deposition to form sedimentary rock, and by volcanic activity. The section clearly shows how the volcanic rock has been forced under pre-existing sedimentary rock. This was a unequivocal proof of an idea which up until then was only a theory – and widely disbelieved in the scientific community.
Hutton also observed that in some rock outcrops, there was evidence that sedimentary rocks were no longer horizontal but hade been forced out of shape by geological forces. These rocks had then been eroded and other sedimentary rock laid down on top.
From this, he deduced that the Earth was a system constantly evolving through erosion, deposition and volcanic activity. When discussing the development of the Earth, he famously said that there was ‘ … no vestige of a beginning – no prospect of an end’.
The geological term for this formation is an unconformity. Hutton identified many: there are good examples at Jedburgh, just downriver from Jedburgh Abbey, and at Sicca Point on the East Lothian coast, east of Tantallon Castle.
Erosion is a natural process and it is evident in old stone buildings as the stone is weathered away. Global warming and acid rain only tend to make this process more rapid.
Historic Scotland can provide advice on the conservation of stonework. For further information visit our Technical Conservation site.