You are standing at the eastern edge of Beringia. Beringia is the name given to the landmass stretching from eastern Siberia through Alaska to the Yukon.
During Ice Ages of the late Pliocene and Pleistocene epochs (2.6 million – 10,000 years ago), glaciers covered much of the northern hemisphere. Glacial advance and retreat occurred dozens of times over the past few million years. There were local mountain glaciers in Beringia, but the great continental ice sheets that covered the rest of northern North America stopped their westward advance at this spot. Along this stretch of the Klondike Highway, the road cuts through outwash gravel deposited by melt water at the glacial margin. Swift moving currents of the Yukon River have cut through these gravelly deposits, forming the islands you see below.
During glacial periods, global sea level dropped up to 130 m, more than enough to dry out the Bering Strait that now barely separates east and west Beringia. This land mass, or “Bering Land Bridge”, served as an important route of dispersal between North America and Eurasia for plants and animals (including man) until 11,000 years ago when the Land Bridge was once again submerged by the rising sea level. Similar plants and animals occur on either side of the Bering Strait today.
During glacial periods, Beringia was covered by cool, arid grasslands called “steppe”. If you could stand here 15,000 years ago, near the end of the last great glaciation, the vista would be of a dusty and treeless steppe at the edge of the ice sheet. You could spot steppe bison (Bison priscus), Yukon wild pony (Equus lambei), woolly mammoth (Mammuthus primigenius), and other animals adapted for feeding on steppe grasses. Modern ecosystems sustain a relatively small number and diversity of large mammals.
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