A tabular layer of igneous rock dolerite, Whin Sill, or sometimes referred to as “Great Whin Sill”, lies in Northumberland and County Durham, and partially in the North Pennines.
It’s hard to believe that Hadrian’s wall passes right over the top of this massive rock formation. The Sill is a must visit part of the wall to visit as it’s so dramatic to walk over.
It actually stretches from Teesdale up to Berwick, and High Force Waterfall in Teasdale has a major outcrop of the intermittent rock. It is also found at the location of Hadrian’s Wall due to the construction of the Roman wall taking advantage of high-up, rocky cliff lines which are formed by Whin Sill. In terms of Whin Sill geology, three kinds of the Sill actually exists, they were formed by separate magma lava flows, known as Hadrian’s Wall-Pennine Sill, Alnwick Sill and Holy Island Sill. Whin Sill got its name from Northern England quarrymen calling a horizontal body of rock “Sil”, they also called much darker, harder rocks “Whin”. Geologists adopted the term “Sill” in the 19th century and the name as stuck ever since!
Some of the locations which include the Whin Sill rock have, in the past, been popular with rock climbing enthusiasts, places like Holwic Scar and Spindlestone Heugh offer challenging rock faces and crags. However, due to a Juniper disease which can be spread on footwear, climbing, for the foreseeable future, has been banned in some of these areas. Climbers had already agreed to avoid certain routes on these Crags, this is due to preserving the rock face and conservation interests. Not to worry, at least there are plenty of other crags to climb in the region and indoor wall climbing!