A series of cold climatic phases in northwestern Europe, during a time when the North Atlantic was in almost full glacial condition. Dryas I was c 16,000/14,000 BP, Dryas II (Older Dryas) was c 12,300-11,800 bp, and Dryas III (Younger Dryas) was c 11,000-10,000 bp. It is named after a tundra plant. . The increasing temperature after the late Dryas period during the Pre-Boreal and the Boreal (c 8000-5500 BC, according to radiocarbon dating) caused a remarkable change in late glacial flora and fauna.