ALLERD

interstadial, or transient, period of glacial retreat that occurred at the close of the Wrm Glacial Stage in Alpine Europe. Radiocarbon dating techniques indicate that Allerd time began about 12,000 years ago. The Allerd was followed by a period of renewed cold and glacial advance. During the Allerd, the glacial ice front was situated in southern Finland and the central portions of Sweden. Conditions had moderated sufficiently to allow much of the once-barren tundra regions to become forested again. Tundra conditions still persisted, however, in regions near the still-extant ice sheets. In regions south of the ice, forests dominated by pine and spruce or birch existed in different regions. Although cooler than modern climatic regimes, Allerd temperatures were significantly warmer than those that had prevailed during the periods of maximum glaciation. During the Allerd in Britain, glaciated regions were restricted to the Highlands of Scotland. Sea levels were higher during the Allerd than during colder times and approached modern sea levels. They were low enough, however, to keep the Strait of Dover and a large area of the North Sea bottom above water.