Arran

1. Early Times

Geology

The Firth of Clyde in south-west Scotland is big enough to be called an inland sea, bounded on the west by Argyll and the Kintyre Peninsula and on the east by the Ayrshire and Galloway mainland. In the middle of the Firth is an archipelago of islands, the most striking of which are Ailsa Craig and Arran. Arran is the largest, more than four hundred square kilometres in area.

The first thing that you notice about Arran when viewing it from the Ayrshire coast is a marked contrast in silhouette: the north is spectacularly mountainous, with jagged, lofty heights; the south has a much lower profile, appearing from a distance to be almost flat. (It is in fact rolling moorland with its own ups and downs.) The contrast is superficial only in a special sense: the two halves of Arran have actually floated and collided on a kind of basalt surface from almost opposite ends of the earth, in what is known as continental drift.

In Cambrian times, nearly 600 million years ago, there was no Atlantic Ocean, and the northern section of Arran, together with most of Scotland, was a part of what is now Canada. It lay much further south than at present, and the climate was sub-tropical. England and Wales, with what was to be the southern section of Arran, were further south again, in a colder position on the globe.

Throughout the hundreds of millions of years the continents slid together and apart, and oceans opened and closed in very slow motion, with a kind of swirling movement. When the land-masses collided, as they often did, the results were spectacular distortions, folding and crushing of the earth's surface, and orogenies, episodes involving the birth of mountain ranges.

Arran's northern mountains were born during the Caledonian Orogeny, in the Silurian age about 400 million years ago, affecting Scandinavia, Scotland, Greenland and what is now eastern North America. A great stretch of water known as the Iapetus Sea closed up, bringing together Scotland and England with their respective halves of Arran.

Much later, about 65 million years ago (in the 'Tertiary' era), the North Atlantic opened up and the Alps were formed during the Hercynian Orogeny, the result of a collision between Europe and Africa. This was accompanied by intense volcanic activity, which is still going on in Iceland. Both halves of Arran were left on the east of the ocean. The north of the island is the southernmost part of what is known as the Tertiary Volcanic Province, one of the five geological areas into which Scotland is divided. Other parts of the Province include several Hebridean islands and the Ardnamurchan Peninsula.1

The north of Arran is dominated by four clusters of spectacular granite mountains, jagged and craggy. The tallest of these is Goatfell (874 metres), which rises impressively above Brodick Castle to the north of the coastal village of Brodick itself. Above the village and below the granite slopes of the mountain is a high bank, the Thousand-foot (300 metres) Platform, which forms a girdle round the entire northern part of Arran. This platform represents the oldest rocks in the island, the 'Dalradian' schists, dating back to Cambrian times - although the section from Corrie to Brodick also contains younger rocks, two layers of Old Red Sandstone as well as other varieties. It was through the Dalradian schists that in Tertiary times a great eruption of lava burst from depth, forming a 'pluton' (a mass of solidified rock) two kilometres below the surface, where a kind of giant blister or dome formed. Through erosion and pressure from ice this blister weathered into the fantastic shapes of the peaks as we now see them.

South-west of Brodick is the site of an actual surface volcano (the 'Central Ring Complex', an oval area nearly five kilometres in diameter), which in the Tertiary period poured out lava across the southern half of Arran, covering basic Permian and Triassic sandstones.2 This process has created the typical 'organ-pipe' crystalline cliffs of the Arran coastline, with headlands at Drumadoon Point, Brown Head, Clauchlands Point and elsewhere, including the mighty upward curve of Holy Island. At Drumadoon Point a small volcanic vent can be seen, tilted on one side like a ladle in a steel-works, with a faulted lava sheet spreading out in front of it. An almost identical formation is to be seen at the south-west point of the Heads of Ayr on the eastern shore of the Firth of Clyde.

Evidence of widespread eruptions, producing similar cliffs, can be seen all along the eastern rim of the present North Atlantic - in the Faroes, St Kilda, Staffa ('Fingal's Cave') and the Western Isles. In Arran, cataclysmic folding and distortion of the rocks has led to very complex stratification, e.g the inverted succession of strata at the north-eastern coast (North Newton to Corloch), where different layers of rock are arranged in mirror formation around a slate core.3

Much of the surface geology, indeed, consists of mudstone and sandstone of two main varieties, Ordovician and Permian, but at all points throughout the island a kaleidoscopic jumble of layers and epochs is immediately evident to the eye, from Dalradian (Cambrian) and Ordovician to Old Red Sandstone, Carboniferous, Permian, Triassic, Jurassic and Cretaceous through to Tertiary, all in close proximity to one another, with innumerable subdivisions and rarities. Hence Arran has been a geologist's paradise, a prime site for researchers and students, right from the days of the father of Scottish geology, James Hutton (1726-97). Hence too, the present notices warning against damaging rare kinds of stone by too free use of the hammer.

Geological folding relates the rocks of Arran to other formations in the mainland of Scotland, the Cowal and Aberfoyle Anticlines, and more generally to the Highland Boundary Fault.4 This fault passes right through the centre of the granite Goatfell complex, showing the relationship of North Arran to the Scottish Highlands as opposed to the gentler landscape of the south.

One of the ways of telling the age of rocks is by the fossils of creatures embedded in the rocks and revealed by weathering as well as quarrying and mining. For example, an animal that inhabited the area now included in Arran was detected in 1975 by its fossilized spoor, indented in a stretch of sandstone about a kilometre north-west of Laggan. This was a gigantic centipede-like creature, Arthropleura, which grew up to six feet long, although this specimen seems to have been only three feet in length. It may have lived about 320 million years ago, in a coal-swamp habitat in the delta of a large river running through central Scotland. It fed on forest litter and thus was an important contributor to early soil-formation.5

Fossilized tracks of another kind of animal were found in 1992-93 on Levencorroch Hill, and the western shore south of the King's Cave near Drumadoon. This was the Chirotherium, literally 'Hand-Monster', so called because of a fancied resemblance between an enormous human hand and the footprint. The creature appears to have been a predecessor by some hundreds of millions of years of the dinosaurs, not a dinosaur itself. It lived in the Triassic period, and moved on four feet. It may have had a long neck and a small head. One can imagine this creature lurching and squelching through the primeval swamp, going down to drink. It would leave footmarks that dried in the sun. In the course of time these were covered with blown sand later impacted into solid rock: thus a fossil was born.

That the animal lived in a part of the world that later became Arran is of course the result of pure chance: similar tracks have been discovered as far apart as Arizona, Argentina and Europe. No fossil of the actual creature has so far been discovered anywhere, but a likely representation of it is displayed in the Arran Heritage Museum in Rosaburn, Brodick.6

Other fossil remains include plants and bark, creatures such as brachiopods and coral, and bivalves from the Arran coal-measures.7

Intense vulcanism can produce several varieties of gemstone, and precious and semi-precious stones have often been found in Arran. Among these are sapphires (of rather uncertain quality) discovered near the Rosa Burn. Quartzes include rock crystal, citrines and amethyst, and topaz, beryl, garnet and tourmaline have been found, as well as agates, chalcedony and opal.8

The Ice Ages

Æons after the last major volcanic outbreaks, the great Ice Ages set in. The phases of these are measured in thousands rather than millions of years, and provide an intelligible time-scale against which the history of humans in these islands can be measured. The latest intense glaciation (the 'Devensian') appears to have reached a maximum over most of Scotland and North England about 23,000 or 22,000 BC. The ice then started a long period of gradual retreat northward, punctuated by pauses and even 're-advances'. Its withdrawal left a landscape recognizably modern, including valleys gouged out and hills rounded and depressed by the great weight of ice sometimes kilometres thick. The word 'nunatak' (taken from the Inuit language) has been used to describe the topmost bits of mountains sticking up from the ice cover, as for example in the present Greenland: the peaks of Northern Arran may have been nunataks...