Oxygen began to appear in the Earth's atmosphere 2.4 billion years ago due to
A) volcanic eruptions.
B) crustal rifting.
C) photodissociation of water.
D) biological activity of plants and bacteria.

Question

Quizplus · Accepted Answer

Oxygen began to accumulate in Earth's atmosphere largely due to the biological activity of cyanobacteria (and later plants) that photosynthesize, splitting water molecules and releasing oxygen as a byproduct. This event is known as the Great Oxidation Event.

Oxygen Began to Appear in the Earth's Atmosphere 2