Evolution of the Atmosphere

Question 1

What happened in Phase 1?

Answer 1

1) The earth’s surface was molten due to the many volcanoes erupting.
2) The surface cooled and a thin crust was formed.
3) The volcanoes continues to erupt and emitted carbon dioxide, water vapour and nitrogen.
4) After, the earth contained mostly carbon dioxide and almost no oxygen.
5) Water vapour soon condensed and formed oceans.

Question 2

What happened in Phase 2?

Answer 2

1) Carbon dioxide dissolved into the water.
2) Marine organisms developed and used up the carbon dioxide. However, when the organisms died they were buried under the ocean’s sediment.
3) The carbon dioxide was then taken into the rocks and carbonate.
4) Green plants and algae evolved and used photosynthesis to remove carbon dioxide and produced oxygen.

Question 3

What happened in Phase 3?

Answer 3

1) The build up of oxygen killed organisms that couldn’t handle it and allowed more complex organisms to develop.
2) Oxygen created the o-zone layer which blocked harmful rays from the sun.
3) This allowed human beings to develop.
4) 200 million years later, the earth’s atmosphere is more tolerable and contains 78% nitrogen, 21% oxygen, 0.04% carbon dioxide, water vapour and argon.