Beringia is a prehistoric geographical region, defined as the land and maritime area bounded on the west by the Lena River in Russia; on the east by the Mackenzie River in Canada; on the north by 72° north latitude in the Chukchi Sea; and on the south by the tip of the Kamchatka Peninsula. It includes the Chukchi Sea, the Bering Sea, the Bering Strait, the Chukchi and Kamchatka peninsulas in Russi The remains of Late Pleistocene mammals that had been discovered on the Aleutians and islands in the Bering Sea at the close of the 19th century indicated that a past land connection might lie beneath the shallow waters between Alaska and Chukotka. The underlying mechanism was first thought to be plate tectonics, but by 1930 changes in the ice mass balance which led to global sea-level fluctuations were viewed as the cause of the Bering land bridge. In 1937, Eric Hultén proposed that around the Aleutians and the Bering Strait region were tundra plants that had originally dispersed from a now-submerged plain between Alaska and Chukotka, which he named Beringia after Vitus Bering who had sailed into the strait in 1728. The distribution of plants in the genera Erythranthe and Pinus are good examples of this, as very similar genera members are found in Asia and the Americas. American arctic geologist David Hopkins redefined Beringia to include portions of Alaska and Northeast Asia. Beringia was later regarded as extending from the Verkhoyansk Mountains in the west to the Mackenzie River in the east. During the Pleistocene epoch, global cooling led periodically to the expansion of glaciers and the lowering of sea levels; these processes created land connections in various regions around the globe. Today, the average water depth of the Bering Strait is 40–50 m (130–160 ft); therefore the land bridge opened when the sea level was more than 50 m (160 ft) below the current level. A reconstruction of the sea level history of the region indicated that a seaway existed from c. 135,000 – c. 70,000 YBP, a land bridge from c. 70,000 – c. 60,000 YBP, an intermittent connection from c. 60,000 – c. 30,000 YBP, and a land bridge from c. 30,000 – c. 11,000 YBP, followed by a Holocene sea level rise that reopened the strait. Post-glacial rebound has continued to raise some sections of the coast. The last glacial period, commonly (and inaccurately) referred to as the "Ice Age", spanned 125,000–14,500 YBP and was the most recent glacial period within the current ice age, which occurred during the last years of the Pleistocene epoch. The Ice Age reached its peak during the Last Glacial…

Beringia The Bering land bridge joined present-day Alaska and eastern Siberia at times during the Pleistocene ice ages. Its greatest extension was about 1,000 miles (1,600 km) north to south. It was not glaciated because snowfall was extremely light as the winds from the Pacific Ocean lost their moisture over the fully glaciated nearby mountains. The grassland steppe, including the land bridge, that stretched for several hundred miles into the continents on either side has been called Beringia. It is believed that a small human population of at most a few thousand survived the ice age in Beringia. It was isolated from populations in Asia for at least 5,000 years. Sometime after 16,500 years ago, it started to populate the Americas when the American glaciers that blocked the way southward melted.[1][2][3][4] Geography The Bering Strait, the Chukchi Sea to the north and the Bering Sea to the south, are all shallow seas (maps, right). During cycles of global cooling, such as the most recent ice age, much water became concentrated in the ice caps of the Arctic and Antarctica. The drop in sea levels exposed shallow sea floors that have subsequently re-flooded.