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| 1 September 2012 This graph shows a timeline of the formation of the Earth, in the molten stage, starting about 4.6 billion years ago. Rocks, oceans, and the first bacteria appeared around 4 billion years ago. At 2 billion years ago oxygen levels increased and multi-cellular organisms appeared. Then came algae and slightly over half a billion years ago the first hard-shelled animals appeared after which came dinosaurs and land plants. At that time, half a billion years ago, the first soil began to form on Earth. |
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