Jackson, Ian. Cumbria Rocks — 60 extraordinary rocky places that tell the story of the Cumbrian landscape. Newcastle upon Tyne : Northern Heritage, 2022.
The richly illustrated and accessible book series of Cumbria, Northumberland and Durham Rocks are available to purchase from Northern Heritage.
Theme: Climate and landscape change
44 Slater Bridge — roche moutonnée. 600 metres walk south from Little Langdale
A few metres north of Slater Bridge in Little Langdale is a rocky knoll. Its western end is a gentle slope of bare, smoothed rock. Over the wall at the eastern end is a little crag.
Look closer and you see the smooth surface is scratched, a fact much appreciated by geologists, as unlike Antique Roadshow experts, rock men like a little wear and tear. Rocks like this help us to understand what our landscape has experienced in the past. This rock is composed of 450-million-year-old volcanic material, but its shape and the smooth and scratched surface are much more recent. These features are evidence that this place was once under a glacier several hundred metres thick which moved down the valley scraping and grinding everything beneath it. The scratches on it are called striations, they are caused by grit and stones embedded in the base of the ice steadily sanding down the bedrock. The gentle western slope and the crag at the eastern side show how the glacier rode over the hill and then “plucked” the rock at its lee end. Rocks with this shape are called roche moutonnée. Not because they resemble sheep but because they look like an 18th century Frenchman’s wig, which was apparently smeared with mutton fat to make it sleek. Rather them than me.
You can find rocks like this all over the Lakes, they and features like ‘U’ shaped valleys and moraines are clues to our frozen past 20,000 years ago. Slater Bridge has been described as the most beautiful bridge in the Lake District. It is a delicate stone arch and a flat span made of a single thin slab of slate, both connected by another glacially smoothed rock. The bridge was constructed by quarrymen 300 years ago to shorten their journey to work.