Click on the dates to learn about some of the major events in Earth's history—from present to 4.8 billion years ago.
History of the Earth
4.8 billion years ago The solar system, including the planet Earth, was born.
3.8 billion years ago The oldest rocks date from this time.
3.5 billion years ago The first life appeared. Colonies of photosynthetic bacteria formed hard calcium carbonate mounds called stromatolites.
2.2 billion years ago Oxygen levels in the atmosphere increased dramatically.
1.8 billion years ago The first eukaryotic cells (cells with nuclei) appeared.
560 million years ago The first animals evolved. These animals had soft bodies and lived in the oceans.
520 million years ago A huge number of new animals evolved, including the first animals with hard skeletons. Trilobites were abundant.
440 million years ago Fish and coral reefs spread through the oceans. Plants and animals, including relatives of spiders and centipedes, colonized the land.
300 million years ago Lush swamps known as “coal swamps” covered the land. The Appalachian Mountains formed when the continents Godwanaland and Laurasia collided.
245 million years ago The largest mass extinction ever claimed most of the marine organisms. Most of the land on Earth is contained in the single supercontinent, Pangea.
200 million years ago Dinosaurs, including the giant long-necked sauropods, ruled the earth. Sharks, ichthyosaurs, and giant marine scorpions ruled the seas.
160 million years ago The first mammals evolved. This is the oldest age of the Pacific crust.
100 million years ago Flowering plants appeared. Tyrannosaurus rex roamed the earth.
65 million years ago Dinosaurs go extinct. Pangea has broken up into present day continents. The Rocky mountains form.
20 million years ago Large mammals increase in importance. Grasslands and deserts form in the middle of continents.
3.5 million years ago Evidence of the oldest human ancestors date from this time.
230 thousand years ago The first Homo sapiens (upright humans) evolved.