Earth History

The Cretaceous-Paleogene (K-Pg) extinction event 66 million years ago did not only kill non-avian dinosaurs — it eliminated approximately 75% of all species on Earth, including many marine reptiles (mosasaurs, plesiosaurs), flying pterosaurs, ammonites, and countless plant and invertebrate species. Survivors included small mammals, birds, crocodilians, turtles, snakes, and frogs — groups that could shelter underground, burrow, or tolerate the sudden darkness and cold.

Dinosaur fossils have been found on all seven continents, including Antarctica. The Antarctic continent, once part of the supercontinent Gondwana, was warmer during the Mesozoic era and supported a variety of dinosaur species. Fossils of Cryolophosaurus ('frozen crested lizard'), a large theropod, were discovered there in 1991. During the Triassic period, all continents were joined as Pangaea, allowing dinosaurs to spread across the entire land mass.

About 66 million years ago, an asteroid roughly 10 kilometres wide struck the Yucatán Peninsula in present-day Mexico at the Chicxulub crater site. Travelling at around 72,000 km/h, it released energy equivalent to billions of atomic bombs, triggering wildfires, a years-long nuclear winter, and the extinction of about 75% of all species — including all non-avian dinosaurs.

Non-avian dinosaurs first appeared around 230–240 million years ago in the Triassic period and went extinct 66 million years ago. That means they ruled Earth for approximately 165 million years — compared to modern humans, who have existed for only about 300,000 years. To put it in perspective, T. rex and Stegosaurus are separated by more time than T. rex and us.

About 335 million years ago, Earth's landmasses were joined in a giant continent. Over millions of years, plate tectonics caused Pangaea to break apart, slowly drifting to form the continents we know today.

Throughout its history, Earth has undergone periods where a significant portion of its species disappeared rapidly. These events were caused by factors like asteroid impacts, massive volcanic activity, and abrupt climate shifts.

The layers of rock exposed in the Grand Canyon contain marine fossils and sedimentary structures, indicating that the area was submerged under shallow seas multiple times over hundreds of millions of years before its uplift and erosion formed the canyon we see today.