About 3.5 billion years ago
Earth was covered by one gigantic reddish ocean. The colour came from hydrocarbons.
The first life-forms on Earth were Archaea (single-celled microorganisms with a structure similar to bacteria) that could live without oxygen. They released large amounts of methane gas into an atmosphere that would have been poisonous to us.
About 3 billion years ago
Erupting volcanoes linked together to form larger landmasses. And a new form of life appeared - cyanobacteria, the first living things that used energy from the sun.
Some 2 billion years ago
The cyanobacteria algae filled the air with oxygen, killing off the methane-producing Archaea. Coloured pools of greenish-brown plant life floated on the oceans. The oxygen revolution that would someday make human life possible was now underway.
About 530 million years ago
The Cambrian explosion occurred. It's called an explosion because it's the time when most major animal groups first appeared in our fossil records. Back then, Earth was made up of swamps, seas, a few active volcanoes, and oceans teeming with strange life.
More than 450 million years ago
Life began moving from the oceans onto dry land. About 200 million years later dinosaurs began to appear. They would dominate life on Earth for more than 150 million years.
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