During the last Ice Age, Swaledale was ridden over by a thick sheet of ice which smoothed the contours, broadened the valley and diverted the course of the River Swale at Keld and Round Howe. Kisdon Hill, the isolated area of upland (498m) that lies within the upper valley, was formed when the melting glacial rivers cut out a new course for the River Swale along what is now known as Kisdon Gorge. Glacial retreat moraines, which held back temporary glacial lakes, are in evidence at Gunnerside Bridge, Lower Whita Bridge, below Grinton Bridge and by Ellerton Abbey.
Glaciers erode the bedrock through the processes of plucking and abrasion. When large boulders become trapped in the base of an ice flow they can gouge grooves into underlying rocks that are parallel to the direction of flow. © Stuart Jones, 2022.
