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. An island chain dubbed Avalonia rose at 60 degrees S on a platform of volcanic rocks and granite.
When the continents joined in Pangaea - "All Earth" - Avalonia's shores ground up against the bulge of equatorial Africa. Dinosaurs roamed this new world crossing freely from one landmass to another, until the crustal plates began to tear apart.
Early Cretaceous Dinosaurs in Gondwanaland
North America rifted from Africa. A trench opened for the waters of the North Atlantic that ebbed and flowed for one hundred and eighty million years as the ocean floor spread. Only twenty million years ago did the Avalonian terrane begin to resemble the land we see today.
USGS, Understanding Plate Motions
The ice sheet moved slowly, only a few inches or a few feet a day, but move it did.
At the place where the glacier was born, the ice dome rose two miles into the sky. Impelled by its own weight, the juggernaut spread outwards.
Global warming turned meltwater runnels into torrents that carved out channels, bored into crevasses and drove passages through ice. Rushing streams deposited till along the glacier's terminus and margins forming ridged moraines.
Meltwater streaming through subglacial conduits left serpentine tunnels strewn with sand, gravel and mud; when the ice casts melted away, long sinuous eskers snaked across the earth.
Eskers (Lake Maurice National Park, Canada.)
Ice cliffs broke away to stand like megaliths on the new ground, until the sun melted the blocks leaving kettle-shaped holes to form lakes and ponds.
The destroyer became the builder. The glacier worked the mounds over and over, smoothing and rounding them into elongated drumlin hills that remained buried in ice.
Mastadon and woolly mammoth found refuge along the coastal corridor. Giant short-faced bears and five hundred pound beavers joined the migration to the open spruce forest and lush grasslands flourishing on the continental shelf.
Twenty thousand years ago, while pioneers of the ice frontier braved Beringia, a continent away Stone Age hunters with Clovis-like weapons preyed on herds of horses running free south of the European ice-shelf.
Known to us as Solutreans, from the paleolithic site of Solutré in south-west France.
Solutrean horse-hunters, courtesy Old Stone Age
Dr. Dennis Stanford focused his attention on the seemingly impossible voyage of a Stone-Age Columbus: Answers came from the likeliest of all places and people, the Eskimos of Barrow, Alaska. As in ages past, the Eskimos still take to the sea in whaling boats crafted with sealskin and wood and bound with caribou sinews.
Eskimo Family, Wikipedia/National Geographic
When Stanford showed an Eskimo woman a bone needle, she saw nothing extraordinary in the item, similar to needles her own grandmother used to sew caribou garments with waterproof seams. “This needle is 20,000 years old,” said Dr. Stanford, the relic from the Solutreans who would’ve used such needles to fashion clothing for their long voyage.
Solutrean needle and fish hook, Wikipedia
No finds were are dramatic than those at Topper in Allendale County, South Carolina.
In 2002, Topper artifacts returned a radiocarbon dating of 16,000-20,000 years ago. Two years later, stone age tools embedded in a white sand stone with a layer of charcoal dated to 50,000 years ago.
Topper artifacts, courtesy Topper Site Virtual Museum
In the 1970s, one of the earliest challenges to the Clovis Firsters came from James Adovasio excavating below the 13,500-year level at Meadowcroft Rockshelter in Pennsylvania: Adovasio’s meticulously detailed analysis dated occupation of the shelter to 16,000 years ago.
Meadowcroft Rockshelter photo, Mark McConaughy
Meadowcroft excavation site enclosure. Examination of the site revealed fire pits and large burned areas of fire floors, refuse and storage pits, concentrations of stone artifacts, ceramics and bone that suggest the presence of specialized work areas, and roasting pits.
Meadowcroft Excavation Site, courtesy Heinz History Center
Clovis point spearhead that transfixed American archaeologists for sixty years was uncovered in a dried up lake bed near Clovis, New Mexico in 1929.
Mammoth bones found in the proximity enabled scientists to date this kill to 13,500 years ago, making the projectile then the oldest Stone Age artifact discovered on the continent.
Clovis Point photo, courtesy National Park Service
Cahokia, A.D. 1150, citadel of a Mississippian mound-building culture outside present-day St. Louis, Missouri: Already occupied for five hundred years, the mid-twelfth century saw the Golden Age of Cahokia, then larger than London and possessing 20,000 residents.
Cahokia Mounds State Historic Site, artist Art Grossman
Quivira, A.D. 1540, the "El Dorado" sought by the conquistador Francisco Vásquez de Coronado on his expedition from Mexico City north to Tierra Neuva. Coronado penetrated the heartland crossing endless plains through Texas, Oklahoma and into Kansas.
Coronado Sets Out to the North by Frederic Remington, Wikipedia