earths atmosphere Flashcards
what has scientist used to reconstruct what the earth used to be like
planets and their moons
gases trapped in ancient rocks
how was the early atmosphere formed
lots of intense volcanic activity, volcanoes released CO2, nitrogen and water vapour and these gases formed the early atmosphere
how were oceans formed
the water vapour condensed as the earth cooled down and fell as rain, the water was then collected in the crust as rocks solidified and it formed oceans
how were water supplies added to oceans
icy comets rained down on the surface as the earth and melted increasing it water supplies
what planets are was the earths early atmosphere similar to and why
venus and mars, as it consisted of mainly carbon dioxide with little or no oxygen gas and traces of nitrogen, ammonia, water vapour and methane
how much nitrogen is in the atmosphere
78%
how much oxygen is in the earths atmosphere
21%
when was the earth formed
4.6 billion years ago
how did oxygen levels rise in the earths atmosphere
2.7 billion years ago bacteria and other simple organisms formed
algae used energy from the sun to make their own food by photosythesis —— increased oxygen ——- more plants evolved , took CO2 from air released 02
what was the con of increased oxygen levels
some microorganisms died as they could not tolerate the high conc of 02 as they evolved without it
what removed C02 from atmosphere
- oceans
- photosynthesis
- skeletons, shells and sedimentary rocks
how has photosynthesis removed CO2 from atmosphere
1) C02 and H20 taken in by plants which was converted into C6H1206 and 02 by photosynthesis
2) C in C6H1206 was stored in plants, when animals ate plants the C would be transferred to animal tissue including their skeletons and shells
how has skeletons, shells and sedimentary rocks removed CO2 from atmosphere
- marine animals died and their shells and skeletons built at the bottom of oceans, then become covered in layers of fine sediment, these layers cause pressure and under the pressure sedimentary rocks are formed
how has oceans removed CO2 from the atmosphere
- some of the CO2 gas dissolved in ocean as it reacted with metal oxides which made insoluble carbonate compounds and they fell into the seabed as sediment and helped form more carbonate rocks
how were fossil fuels formed
by the remains of animals and plants being crushed by large scale movements of the earth and it being heated by the earth
how was coal formed
- it was formed from thick deposits of pant material when they died in swamps and compressed over million years
how was crude oil and natural gas formed
it was formed when the remains of plankton were deposited on the seabed, then covered by sediments ad compressed to form rocks, the crude oil and natural found trapped beneath the layers of rock
how was methane and ammonia removed from the atmosphere
any methane and ammonia found in the early atmosphere reacted with oxygen, this removed the methane and ammonia from the atmosphere
why is there a high level of nitrogen in the atmosphere
as nitrogen is an unreactive gas
main greenhouse gas
CO2, water vapour and methane
how much CO2 is in the atmosphere
0.04%