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Friday, 13 June 2014

Beneath your feet lies an age-old tale- ending still developing
As you lie in your tent at Lochranza Campsite you sleep on alluvial soil and gravel deposited by water. The Lochranza area 6,000 years ago would have been a broad estuary with sea levels higher than they are now due to meltwater from the glaciers of the most recent Ice Age. The last ice was receding from about 15,000 years ago.
As you stand at Newton Point on the North shore of the loch you will notice the ‘raised beach’ with its line of cliffs standing inland from the sea. This phenomenon, which can be seen all round Arran, is due to the rebound of the land after being released from the weight of the glaciers.
When the ice sheets moved over Arran they gouged out U-shaped valleys such as Glen Sannox and Glen Rosa and carved knife-edge arĂȘtes such as the A Chir ridge. The ice also carried and deposited huge boulders known as erratics- you can see one, the Clach a Chath, on the roadside between Sannox and Corrie. Whilst you’re in Corrie you’ll notice the pink rocks that form the seashore. The rock is 270 million year old red Permian sandstone. If its wave-like shapes make you think of sand dunes that’s because these rocks were formed in desert conditions in the southern hemisphere.
Travelling the two miles between Lochranza and Catacol you will observe the oldest rocks of the island. Once they were muds and silts at the bottom of the ocean but they have been twisted, folded and baked over time. Look out for veins of quartz in them. These 600 million year old Dalradian rocks are the same as those which form the Great Glen of Scotland. During this geological period Scotland and England collided in the southern hemisphere.
Arran is well-known as ‘Scotland in Miniature’- an epithet which reflects its geological history. 400 million years ago a huge fracture in the earth’s crust pushed the Highland Dalradian rocks against younger rocks creating the contrast between the northern and southern landscapes of the island.
Only 60 million years ago the Arran we know today was shaped. At that time cracks in the earth’s surface opened up under what is now the Firth of Clyde and the Atlantic Ocean formed. As north-west Britain was still attached to North America and Greenland, whilst the rest of Britain was joined to Europe, this means that Arran has actually been an island for longer than Britain. The movements in the earth’s surface triggered two caldera volcanoes in the North of Arran. The cooled magma became the granite that forms Arran’s distinctive mountain ridges and tors with their resemblance to Jenga towers. Magma erupting sideways in cracks of the earth also created rock sills such as the Drumadoon cliffs at Blackwaterfoot.
 The man who began to make sense of tumultuous geological Earth history is closely associated with Lochranza. In 1787, whilst overseeing the construction of the Forth and Clyde canal, James Hutton began to develop his idea that the Earth must have taken millions of years to form and be the result of mighty natural forces. His ideas were considered radical and heretical in a Christian society. The stretch of coast that inspired his understanding is 300 metres on from Newton Point and is known as Hutton’s Unconformity. Look for schist leaning one way and sandstone leaning the other despite originating from different times and places. Hutton realised only great upheavals of the earth’s surface could have caused rocks of all ages which had formed in different ways to lie closely aligned. Regarded as one of the fathers of the study of geology, he revealed knowledge of the Earth that’s anything but set in stone.
Information from:
The Isle of Arran Heritage Museum geology section
Arran and the Clyde Islands by Scottish Natural Heritage and the British Geological Survey
The photos show 1.Volcanic influence on Arran in granite on Cir Mhor, and 2. The rounded hills of ancient folded Highland rocks at Lochranza.

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