The evolution of the atmosphere

Question 1

Theory for how the earth’s atmosphere evolved
phase one

Answer 1

• The first billion years of the earths history was pretty explosive , the surface of the earth was covered in volcanoes which erupted and released lots of gases = we think this is how the earths atmosphere was formed
• The early atmosphere was probably mostly co2, virtually no 02, similar to mars and Venus today
• Volcanic activity also released lots of nitrogen, which built up in the atmosphere over time as well as water vapour,
  and small amount of methane and ammonia.

Question 2

Theory for how the earth’s atmosphere evolved
phase 2

Answer 2

1) when the water vapour in the earth atmosphere condensed it formed the oceans

2) lots of co2 was removed from the atmosphere as it dissolved in the oceans. The dissolved co2 then went through a series a reactions to form carbonate precipitates that formed sediments on the seabed

3) Green plants and Algae evolved and absorbed some co2 to carry out photosynthesis, later marine animals evolved and their shells, and Skelton contained carbonates from the ocean.

4) Some of the carbon, these organisms absorbed from the atmosphere and oceans became locked in rocks and fossil fuels after the organism died.

Question 3

Give examples of : Some of the carbon, these organisms absorbed from the atmosphere and oceans became locked in rocks and fossil fuels after the organism died.

Answer 3

• When ancient organisms ( Plankton, marine animals) die, they fall to the sea bed and get buried by layers of sediment. Over millions of years they form into sedimentary rocks, oils and gases. - trapping carbon within them and helping to keep co2 levels reduced in atmosphere
• Things like coal, crude oil and natural gas are made by process called ‘fossil fuels’
• Crude oil and natural gases are formed from deposits of plankton. These fossil fuels form reservoirs under the seabed where they’re trapped in rocks
• coal is a sedimentary rock made from thick plant deposits
• Limestone a sedimentary rock made mostly of calcium carbonate deposits from the shells, skeletons of marine organisms

Question 4

Theory for how the earth’s atmosphere evolved
phase three

Answer 4

1) as well as algae and green plants absorbing co2 in the atmosphere ( oceans) , they also produce oxygen by photosynthesis - ( when plants use light to convert co2 and H20 into sugars

6co2 + 6H20 -> C6H12O6 + 602

2) Algae evolved first - around 2.7 billion years ago then over the next billion years , green plants evolved

3) As oxygen levels in the atmosphere built up over time, more complex life evolved

4) Eventually, around 200 million years ago, the earths atmosphere reached a composition similar to that of today.
Around apx 80% nitrogen 20% oxygen and small amounts of other gases,mainly co2, noble gases and water vapour