Evolution of the atmosphere

Question 1

What happened in the first billion years of the Earth’s atmosphere?

Answer 1

• Lots of volcanic activity meant that the Earth was very dry
• Volcanic activity released lots of carbon dioxide, water vapour and nitrogen in the air
• Atmosphere was made up mostly of CO2

Question 2

What happened to the water vapour and CO2 from the early atmosphere?

Answer 2

• Earth began to cool down
• Water vapour condensed into water to form the ocean
• Carbon dioxide was dissolved in the ocean and then went on to form sediments on the sea bed

Question 3

Why did CO2 levels decrease and O2 levels increase?

Answer 3

• Algae began to appear and green plants evolved
• Plants carried out phostosythesis which absorbed carbon dioxide and released oxygen
• This allowed more complex life forms to evolve

Question 4

What happened when algae and green plants died?

Answer 4

• Could only hold little amount of CO2 in their body
• When they died, they fell to the sea bed and became buried in layers of sediment
• Over millions of years, this sediment became compressed to form sedimentary rock, oil and gas
• Sedimentary rock, oil and gas trapped the carbon dioxide to stop it from getting back into the atmosphere

Question 5

What was used to form crude oil and gas?

Answer 5

• Dead plankton

Question 6

What was used to form coal (sedimentary rock)?

Answer 6

• Dead plant material

Question 7

What was use to form limestone (sedimentary rock)?

Answer 7

• Dead animal shells and skeletons