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What events shaped Earth during the Hadean Eon?
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geologic history of Earth
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The Hadean Eon (approximately 4.6 to 4.0 billion years ago) was a period of intense transformation that shaped the early Earth. Key events included:
- Accretion and Differentiation: Earth formed through the accumulation of dust and gases and frequent collisions with planetesimals. During this time, the planet differentiated as heavier elements like iron sank to form the core, while lighter elements like silicon rose to form the crust.1
- Intense Bombardment: Frequent impacts from extraterrestrial bodies released massive amounts of heat, likely keeping the surface in a molten state for much of the eon. This period was part of a broader era of heavy bombardment in the early solar system.12
- Formation of the Moon: The leading theory suggests the Moon formed when a Mars-sized celestial body collided with Earth, ejecting material that eventually coalesced.1
- Atmospheric and Oceanic Development: While debated, evidence from zircon grains suggests that stable continents, liquid water, and an atmosphere may have existed by 4.4 billion years ago. The atmosphere evolved through volcanic outgassing and the potential delivery of water via comet impacts.1