Key learning points

1. Early volcanic activity is thought to have made an atmosphere of carbon dioxide and nitrogen billions of years ago.
2. Carbon dioxide can dissolve in oceans and form carbonates which, over millions of years, can form sedimentary rock.
3. The amount of carbon dioxide was reduced by the formation of sedimentary rocks and photosynthesis by algae and plants.
4. Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis.
5. Phytoplankton in the oceans are responsible for roughly half of all oxygen production that takes place today.

Keywords

• Volcano - A volcano is an opening on the surface of a planet or moon through which molten rock, rock fragments and gases erupt.

• Sedimentary rock - Sedimentary rocks are a type of rock formed from the compression of sediments (rock fragments, minerals and remains of dead plants and animals).

• Photosynthesis - The process of photosynthesis is where energy from sunlight is used to convert carbon dioxide and water into glucose and oxygen.

• Algae - Algae are a diverse range of unicellular or multicellular photosynthetic organisms. Many algae are aquatic.

• Phytoplankton - Some types of algae belong to a group of microscopic marine photosynthetic organisms called phytoplankton.

Common misconception