The changing Earth

Most of the Earth's continents were joined together in a single supercontinent known as Pangaea. The continental interiors were hot and covered by vast deserts. Pangaea is the most recent of several supercontinents in Earth's history and was formed when continents collided, which raised enormous mountain ranges at continental boundaries.

The northern continents had begun to separate from the southern continents, forming the Gulf of Mexico and the north Atlantic. Most of Europe was covered by a shallow sea with a few low-lying islands. Earth's climate throughout the Jurassic and Cretaceous was much warmer than today. Forests grew and dinosaurs lived in polar regions because there were no ice caps.

The Americas moved farther west, as Africa and India moved north, and Antarctica and Australia moved south. Very high sea levels at this time created inland seas that crossed continents. North America was cut in half by a sea running from the Gulf of Mexico to the Arctic Ocean.

India began to collide with Asia perhaps as long ago as 55 million years ago, creating the Himalayas, and Africa began to collide with Europe and Asia, forming extensive mountain ranges including the Alps. Australia completely split from Antarctica about 30 million years ago, heading north. Due to the huge amount of water contained in the polar ice caps, sea levels today are close to the lowest they have been in almost 300 million years.