C9 Flashcards
How long have the proportions of gases in the atmosphere been the same for and what are they?
200 million years
4/5 nitrogen =80% (approximately)
1/5 oxygen=20%(approx)
small proprtions of other gases eg CO2, water vapour and noble gases.
Why is evidence for the early atmosphere limited?
Because theories about how the atmosphere was formed have changed and developed over 4.6 billion years.
What is stage 1 of the evolution of the atmosphere theory?
There was instense volcanic activity that realeses lots of gases which made earths early atmosphere.
Why was the start of phase 1 of the earths early atmosphere similar to Mars and Venus?
Becacuse it consisted of mainly carbon dioxide with little oxygen.
What did volcanoes also produce?
Volcanoes also produced nitrogen, which built up in the atmosphere over time, as well as water vapour and small amounts of methane and ammonia.
How were seas and oceans formed?
Water vapour in the atmosphere condensed to make the oceans.
How are levels of carbon dioxide in the atmosphere reduced (oceans)?
When oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments (limetsone- a calcium carbonate made of shells and skeletons of marine animals).
How did algae and plants decrease the percentage of carbon dioxide?
By evolving and carrying out photosynthesis
How else was carbon dioxide decreased?
By the formation of sedimentary rocks and fossil fuels (coal,crude oil, natural gas which all contain carbon).
How are crude oil, coal and natural gas formed?
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 to form sedimentary rocks(coal), crude oil and natural gas- trapping the carbon within them.
What is the differences between how crude oil and natural gas is formed and how coal is formed?
Crude oil and natural gas formed of deposits of plankton and form reservoirs under the seabed when they get trapped in rocks.
Coal is a sedimentary rock made from thick plant deposits.
How did the levels of oxygen increase and when?
Algae first produced oxygen 2.7 billion years ago (photosynthesis). Over the next billions of years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.
What do greenhouse gases do?
Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.
Name 3 greenhouse gases?
Water vapour
Carbon dioxide
Methane
Explain the greenhouse effect?
1)The sun gives out short wavelengh radiation which is re-emitted back by the earth as long wavelengh radiation.
3) The long wavelengh radiation is absorbed by the greenhouse gases in the atmosphere.
4)Greenhouse gases re-radiate the heat in all directions including back to earth causing the temperature to rise.