Jackson, Ian. Northumberland Rocks — 50 extraordinary rocky places that tell the story of the Northumberland landscape. Newcastle upon Tyne : Northern Heritage, 2021. The richly illustrated and accessible book series of Northumberland, Cumbria and Durham Rocks are available to purchase from Northern Heritage.
15 Holy Island
Theme: Volcanoes and molten rock
Location
Just off the coast, south of Berwick upon Tweed and north of Alnwick
Description
On this small island, also known as Lindisfarne, there are lots of special rocky places to visit. But, because it is fundamental to the existence and heritage of the island, the focus here will be the Whin Dyke.
Like the Whin Sill suite of rocks, of which it is part, the Whin Dyke is a hard igneous rock called dolerite, injected vertically into existing Carboniferous sedimentary rocks. Where the Dyke cuts like a black blade across the foreshore, defining the south side of the Heugh, look out for fossils of crinoids and brachiopods in the adjacent limestone.
Near the castle you can also visit some of the largest limekilns in Northumberland and then walk north to see the limestone which they quarried near Nessend and burnt in the kilns. At Snipe Point there are stunning rock troughs and domes where the rocks have been folded.
While the igneous and sedimentary rocks are the bedrock of Lindisfarne, the overall shape of the island today is very much influenced by much more recent wind-blown sand dunes which are less than 6000 years old.
The Whin Dyke is in many ways the physical foundation of Lindisfarne’s heritage. Without it there would have been no island for St Cuthbert’s Hermitage, no settlement of the Heugh, and no site for the castle…… and a lot less visitors today.
The dolerite is hard, so weathers and releases nutrients slowly, and on its shallow soils in dry seasons the vegetation can be physically-stressed. On the Heugh is a distinctive set of species, with common rock-rose and several uncommon clovers including slender trefoil and rough clover.