What gives Scotland its edge?
Scotland’s dramatic coastal cliffs – granite, sandstone, volcanic – are the result of geological forces
over millions of years.
Scotland’s coastline is incredibly varied: a quick glance at a map shows a generally smooth east coast with wide firths and few islands contrasting with the deeply indented west coast with long fjords and many isles of different shapes and sizes.
This is largely due to geology. Sometimes there is an obvious link, for example where Loch Linnhe is eroded along the Great Glen fault, or where tough igneous rocks create islands such as Ailsa Craig, the Bass Rock or St Kilda. Elsewhere, variations in bedrock might be more subtle but accentuated by ice and sea erosion. Differences between layers within the Dalradian metamorphic rocks create long narrow sea lochs in Argyll, for instance.
Often different geological processes have played out over hundreds of millions of years. The islands of the Hebrides exemplify this with an astonishing range of rock types and ages, from the 3,000-million-year-old Lewisian gneiss to volcanic rocks merely 55 million years old. Here, ancient continental crust was stretched and rifted as the Atlantic Ocean opened, accompanied by prodigious volcanic activity creating lava flows and volcanic rocks from Skye to Arran.
Crucially, at the same time, north-west Scotland was uplifted and tilted; subsequent erosion then exposed a layer-cake cut through the Scottish crust, with the oldest rocks in the far north-west overlain by the deep roots of the old Caledonian mountain belt still seen today across the Highlands. This created a high spine of land close to the mainland west coast. These mountains are what makes the west coast wetter. It’s what allowed the build-up of ice during the ice age, eroding the west side of Scotland more intensively than the east.
As James Hutton first recognised at Siccar Point on the other edge of Scotland in 1788, there are younger sedimentary rocks sitting on top of the mountain chain. These formed in the Devonian and Carboniferous periods. In the Devonian rocks are some of the first fossil fish ever recognised and described by the likes of Hugh Miller; in the Carboniferous period, vast swamps helped create the coal that powered the industrial revolution in Scotland in the 18th and 19th centuries.
On the very eastern fringes of Scotland, feather edges of the overlying younger rocks that filled the North Sea Basin offshore have held the oil and gas that sustained the economic growth of Scotland during the 20th century.
The geological wealth and diversity of Scotland’s layer cake explains why the science of geology was born here. It’s why geoscientists come from all over the world to study its rocks. As well as the wild, spectacular and varied scenery too…
Now the skylines reach my eyes
The ridge stands out in highland skies
I just can’t believe I’m going home Runrig – Going Home
‘I’ve always been attracted by edges. Where the land meets the sea, where a meadow meets a forest, where saltwater meets fresh. You get extra insights. You can see further from an edge.’ Jim Dixon
Image: Eshaness, Shetland
by Jason Gilchrist jasongilchrist.co.uk
Find out more about the amazing variety of Scotland’s geology – including top spots for viewpoints throughout the country – at ScottishGeology.com.