How did earths atmosphere become oxygen-rich?

Answer 1

Biological activity

Answer 2

This was an abrupt change caused by algae discovering photosynthesis. The magic here is using photosynthesis to split water into H and O. The H molecyles are used by the plant to make carbohydrates, and the O is discharged as a waste gas. The oxygen content may have gone well over 20%, and the algae (and cocoliths) mopped up most of the CO2 and methane, and as a result, the Earth went into a great freeze, Snowball Earth, which lasted most of the time up to the pre-cambrian.

Answer 3

The earth had liquid water H2O. When heated it terns to steam. Since tempature is the average of molecular movement, some fo the " water" is superheated. These molecules bonds are broken -breaking down to two hydrogen and one oxygen. Hope it helps Tyy

Answer 4

Earth's atmosphere became oxygen-rich as a result of photosynthetic organisms, primarily cyanobacteria, releasing oxygen as a byproduct of photosynthesis. Over millions of years, this process gradually increased the oxygen levels in the atmosphere, leading to the oxygen-rich environment we have today.

Answer 5

from stromatolites. they ate sunlight and pooped rocks and developed oxygen in our atmosphere

Answer 6

Biological activity