Beringia is a loosely defined region surrounding the Bering Strait, the Chukchi Sea, and the Bering Sea. It includes parts of Chukotka and Kamchatka in Russia, as well as Alaska in the United States. In historical contexts it also includes the Bering land bridge, an ancient land bridge roughly wide (north to south) at its greatest extent, which connected Asia with North America at various times — all lying atop the existing North American plate, and east of the Siberian Chersky Range — during the Pleistocene ice ages. During ice ages, more water was stored as ice, the sea levels fell, and a land bridge was exposed.