A dramatic sight rising out of England’s deepest lake
Wast Water is famous for its 'screes' - great swathes of dark rubble that blanket the valley side above the lake. On a thundery day they give the valley a dramatic, forbidding feel.
On its south east side, the valley rises steeply some 460 metres above the lake. The top part is a high cliff, with deep chasms cut into the rock from which the boulders have been prized.
Below the cliff, for nearly 300 metres, the scree falls away in great fan-shaped cones of angular rocky debris, each block resting on the one below. Some boulders in the scree can be as large as a metre across but most are much smaller.
The screes were formed by water freezing in cracks in the exposed cliffs. The pressure of the water expanding as it froze, time and time again, gradually forced blocks away from the cliff face and they tumbled downhill. The rocks settled to form a slope of 35° degrees, the stable angle for loose debris.
A great deal of freezing and thawing would have occurred during the last Ice Age and in the tundra-like conditions that existed 14,000 to 10,000 years ago after the glaciers had melted.
Over thousands of years, and with millions of rock fragments, the screes gradually grew up the valley side. They are fossilised now in our warmer climates and little, if any, new scree is being added.