In (million years ago), each unit representing the period of approximately 1,000,000 years in the past. The history of Earth is divided into four great starting 4,540 Ma with the formation of the planet. Each eon saw the most significant changes in Earth’s composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs.
Earth, like most other bodies in the Solar System, formed about 4.5 billion years ago from gas and dust in the early Solar System. The formation of the ocean and the subsequent development of life occurred during the first
billion years of Earth's history. Life spread globally and has been altering Earth's atmosphere and surface, leading to the Great Oxidation Event two billion years ago. Humans emerged 300,000 years ago in Africa and have spread across every continent on Earth. Humans depend on Earth's The Modern English word Earth developed, via Middle English, from an Old English noun most often spelled eorðe.[23] It has cognates in every Germanic language, f