The Devil's Dyke V-shaped dry valley is the result of solifluction and river erosion. More than fourteen thousand years ago, the area experienced an intensely cold climate (but not glacial conditions). Snowfields capped the South Downs. Permafrost conditions meant that the chalk was permanently frozen. In summer, the snowfields melted and saturated the top layer of soil, because the water could not permeate the frozen chalk underneath. Waterlogged material situated above the permafrost slid down the gradient, removing material by friction, exposing deeper layers of frozen chalk. When the Ice Age ended, the snowfields covering the South Downs melted, and rivers formed across Sussex. The Devil's Dyke valley was completed by one such river.