 That is not securely dated, and estimates vary by 400 years, but it is generally accepted to have lasted around 200 years.In northern Scotland, the glaciers were thicker and more extensive than during the Younger Dryas.The Older Dryas, in turn, was preceded by another warmer stage, the Bølling oscillation, that separated it from a third and even older stadial, often known as the Oldest Dryas.