The Evolution of Atmosphere

Question 1

What is believed to have happened during phase 1 of the evolution of the atmosphere?

Answer 1

1)the surface was covered in volcanoes that erupted and released lots of gases (this is how the early atmosphere was formed)
2)the early atmosphere was most likely carbon dioxide with virtually no oxygen
3)volcanic activity also released nitrogen which built up in the atmosphere over time as well as water vapour and small amounts of methane and ammonia

Question 2

What is believed to have happened during phase 2 of the evolution of the atmosphere?

Answer 2

1)when the water vapour in the atmosphere condensed it formed the oceans
2) Lots of carbon was removed from the early atmosphere as it dissolved in the oceans. This dissolved carbon dioxide then went through as series of reactions to form carbon precipitates that formed sediments on the sea bed
3)green plants and algae evolved and absorbed some of the carbon dioxide so that hey could carry out photosynthesis. Later, marine animals evolved and their shells and skeletons contained carbonates from the ocean
4)Some of the carbon these organisms took in from the atmosphere and oceans became locked up in rocks and fossil fuels after these organisms dies

Question 3

How are fossil fuels formed?

Answer 3

-when plankton and marine animals die they fall to the sea bed and get buried by layers of sediment
-over millions of years they become compressed and form sedimentary rocks, oil and gas trapping the carbon within them and helping to keep carbon dioxide levels in the atmosphere reduced

Question 4

What type of rocks are coal and limestone?

Answer 4

Sedimentry

Question 5

What is coal made from?

Answer 5

thick plant deposits

Question 6

what is limestone made from?

Answer 6

it is mostly made from calcium carbonate deposits from shells and skeletons of marine organisms

Question 7

What is believed to have happened during phase 3 of the evolution of the atmosphere?

Answer 7

1) as well as absorbing the carbon dioxide in the atmosphere green plants and algae produced oxygen by photosynthesis
2)algae evolved first around 2.7 billion years ago and then over the next billion years or so green plants evolved
3)as oxygen levels built up i the atmosphere over time more complex life like animals could evolve
3)eventually around 200million years ago the atmosphere reached a composition similar to what it is today: around 80% nitrogen, 20% oxygen and 1% of other gases mainly carbon dioxide, noble gases and water vapour