Oxygenation of the atmosphere
Also called: Great Oxidation Event · Topic: Origin and Evolution of the Earth and the Solar System · NCERT: Class 11, Ch 2 "The Origin and Evolution of the Earth"
Meaning
Oxygenation is how free oxygen built up in the Earth's air. Photosynthesis evolved about 2,500–3,000 million years ago. At first, the oxygen it made saturated the oceans. Then, from about 2,000 million years ago, oxygen began to flood the atmosphere. Beyond NCERT, this rise is called the Great Oxidation Event (about 2.4–2.0 billion years ago). Oxygen also made it possible for the ozone layer to form, which later let life move onto land.
Example
Iron dissolved in seawater reacted with the oxygen and settled on the sea floor as banded iron formations. The iron ore of the Bailadila range in Dantewada district, Chhattisgarh, comes from such rocks.
Don't confuse with
- Origin of life: life began about 3,800 million years ago, in the oceans. Oxygen built up in the air much later, from about 2,000 million years ago.