It began when an arc of volcanoes ruptured the floor of the ancient Iapetus Ocean south of Gondwana, where the continents of Africa and South America lay interlocked. The seabed explosions unleashed a cataclysm of lava and white-hot rocks. An island chain dubbed Avalonia rose at 60 degrees S. on a platform of volcanic rocks and granite.

Plate Tectonics

In tandem with the drifting continents, Avalonia moved north-north-west across the face of the earth. The archipelago converged with the landmass of Baltica carrying the bedrock of Western Europe. Four hundred million years ago, Avalonia and Baltica collided with Laurentia, the cradle of North America.

The Taconic and Acadian Orogenies

The ice sheet was the last and most recent glaciation of North America during two-and-a-half million years of the Pleistocene epoch. The big freeze reached from the Pacific to the Atlantic and flowed southward to 40 degrees N. blanketing the northern half of the continent.

Ice Age

Beringia, the land-bridge that spanned the Bering Straits between eastern-Siberia and Alaska, its connectivity fluctuating with the advance and retreat of the ice mass.

Beringia map, courtesy of Illinois State Museum

For fifteen millennia, the hardy people who will become the ancestors of Native Americans populate the far reaches of Beringia in growing isolation from their primeval Asian lineages.

Between 20,000 - 15,000 years ago, as the earth warms and the ice wall comes down, the long standstill ends. A swift migration of humans and beasts follows, perhaps five thousand people in all, crossing into the New World and moving down the western spine of the Americas as far south as Monte Verde in Chile.

Map courtesy Ripan Mahli, Mahli Molecular Anthropology Lab, University of Illinois