The Evolution of the Atmosphere

How was the early atmosphere formed?

The surface of the earth was covered in volcanic activity -> released lots of gases

What was the early atmosphere made up of?

Carbon dioxide, hardly no oxygen = Atmosphere of Mars or Venus today

What gases did volcanic activity release?

Carbon dioxide, nitrogen, water vapour, methane, and ammonia

How were oceans formed?

Water vapour in the atmosphere condensed

How was carbon dioxide removed from the early atmosphere?

It dissolved in the oceans

What formed when the carbon dioxide dissolved in the oceans?

A series of reactions to form carbonate precipitates that formed sediments on the seabed

What evolved from sediments on the seabed?

Green plants and algae = absorbed some of the carbon dioxide so they could carry photosynthesis

How did marine animals evolve?

Their shells and skeletons contained carbonates from the oceans

What happened to the carbon the organisms took in from the atmosphere and oceans?

Became locked up in rocks and fossil fuels after the organisms

What happens when plants, plankton, and marine animals die?

They fall to the seabed and get buried by layers of sediment over millions of years, they become compressed -> form sedimentary rocks, oil, and gas - trapping the carbon within them and helping to keep carbon dioxide levels in the atmosphere reduced

What is made from the deaths of plants, plankton, and marine animals?

Fossil fuels - coal, crude oil, natural gas

How are crude oil and natural gas formed?

Deposits of plankton - the fossil fuels form reservoirs under the seabed when they get trapped in rocks

What is limestone?

Sedimentary rock, made of calcium carbonate deposits from the shells and skeletons of marine organisms

When did algae evolve?

2.7 billion years ago

What happens to earth when oxygen levels build up via photosynthesis?

More complex life begins to evolve

What is the atmosphere like today?

78% nitrogen
21% oxygen
1% CO2 + noble gases + water vapour