Roughly 20,000 years ago the great ice sheets that buried much of Asia, Europe and North America stopped their creeping advance. Within a few hundred years, sea levels in some places had risen by as much as 10m — more than if the ice sheet that still covers Greenland were to melt today. The ice melted amidst torrential meltwaters, leaving a scarred landscape of rock and glacial debris as in Swaledale. The River Swale and many becks are deeply incised at various sections and many were diverted from their previous courses due to glacial moraines and debris. Climate warmed rapidly, although there was a return to cold conditions between 12,900 and 11,700 years ago. Plants and animals colonised the land and hunter-gatherers probably arrived soon after 10,000 years ago, heralding a new chapter in the evolution of the landscape.