“Across the land, turbulent air flowing from the chilly north encounters the breezes of the hot south. As the two fight it out over the plains, tornadoes are spawned. Ninety percent of the worlds tornadoes occur in North America.” The Eternal Frontier, Tim Flannery, 2001.
Long before it became the first global human empire, North America was a climatic dynamo affecting the entire earth.
Unlike any other continent, it is a giant “inverted wedge”, 4000 miles across the in the sub-arctic north, sixty miles across in the south, with the Appalachian Mountains to the east and the Rockies Mountains to the west. This wedge is a giant. . . carburetor. . . funneling super-chilled Canadian air southward in winter, and warm Gulf air northward in summer, generating explosive storms, torrential rains, giant lakes, thunderous rivers, and intense seasons that have fueled an evolutionary combustion of plants, reptiles and mammals. This includes the great forests of deciduous trees that shed their nutrient-drained colorful leaves in winter , when the sunlight is low, and reabsorb their fertilizer energy in the spring when the sun is bright. And not only leaves, seedlings too, including nutritious, soft-shelled nuts that entice small mammals to carry them away and bury them. North America invented squirrels. Native american societies, too, thrived on the gathering and storing of nuts. Only in North America did inland complex societies arise that were not based on farming.
Sixty five million years ago, North America was two continents separated by a shallow sea, the BearPaw Sea, covering what is now the great plains.
And. . .then. . . a renegade Manhattan-sized meteor from a broken asteroid escaped the gravity of the asteroid belt, and found its way toward Earth. It lunged in from the southeast and across the equator and crashed into what is now the town of Chicxulub, on the Yucatan peninsula. It struck with a glancing blow “like a giant golf chip shot“, at a speed of 54,000 miles per hour, digging a celestial divot straight up into the BearPaw seaway, with a collision blast of a 100 million megatons of TNT, 2 million times greater than the largest nuclear bomb ever made, exploding a hole 3 miles deep and 100 miles wide, and creating a tsunami wave . . . one-half mile high. . . that smashed the whole world. With heat one thousand times that of the surface of the sun, the entire North American forest was ‘carbonized’ – incinerated – all the way to the Red Deer River valley in northern Canada, and even across the Pacific Ocean to Hokkaido island of northern Japan. Fourteen genera of dinosaurs immediately became extinct. The Age of Giant Reptiles cataclysmally ended. The lee of the mountain ranges of the Appalachians and of the Sierra Nevada and inside the Arctic Circle were the only areas of sanctuary for life.
For many, many years, debri, dust, and smoke blocked out the sun, freezing the land, and poisoning the atmosphere with sulfur and acid rain. This was “Impact winter”, the long “polar night”. . .that starved planetary life.
It would be centuries before the charred North America would turn green again, slowly rejuvenated by a. . . fern, Stenochlaena.