Earth 66 Million Years Ago: The Asteroid That Ended the Dinosaurs

66 million years ago, at the end of the Cretaceous period, the continents were close to their modern shapes but not their modern places. The Atlantic Ocean was much narrower, India was an island in the middle of its northward dash towards Asia, and sea levels were high enough to flood large parts of Europe and Africa.

Then an asteroid about 10 km across struck a shallow sea at the edge of what is now Mexico’s Yucatán Peninsula. It hit at around 20 km a second, from the north-east at a steep angle, and dug the Chicxulub crater, about 180 km wide.

The impact threw molten rock around the planet, set off a tsunami that crossed the oceans, lit wildfires and filled the sky with soot and sulfate. Sunlight dimmed for years and temperatures plunged in an “impact winter”. At the same time, the Deccan Traps volcanoes in India were erupting.

About three-quarters of all species died out, including every dinosaur except the birds, the ammonites and the giant marine reptiles. Mammals survived and, in the Paleogene, rapidly spread into the empty niches.