How was oxygen introduced into our atmosphere?

amoebas

Photosynthetic bacteria and small plants

Volcanic outgassing

It’s been there since the Earth was formed

Oxygen was introduced into our atmosphere through a process called oxygenation. This process occurred over billions of years and involved several factors.

One major factor was the evolution of photosynthetic organisms such as bacteria and small plants. These organisms had the ability to use sunlight, water, and carbon dioxide to produce oxygen through the process of photosynthesis. As these photosynthetic organisms became more abundant, they started releasing oxygen into the atmosphere.

Another significant source of oxygen was volcanic outgassing. Volcanic activity on Earth released gases, including water vapor and carbon dioxide, into the atmosphere. Over time, these volcanic emissions also contributed to the presence of oxygen in the atmosphere.

It is important to note that oxygen has not been present in Earth's atmosphere since its formation. Initially, the atmosphere was composed mainly of gases like methane, ammonia, and water vapor. As oxygen-producing organisms evolved and became more abundant, they gradually changed the composition of the atmosphere to include higher levels of oxygen. This process took several billion years and is known as the Great Oxygenation Event.