how much nitrogen is in the earths' atmosphere today?
78%
how much oxygen is in the earth's atmosphere today?
21%
what other gases can be found in the earths atmosphere?
carbondioxide, watervapour,noblegases
why is the evidence of the early atmosphere limited?
because of the timescale of 4.6 billion years.
what events released gases during the first billion years of earths existence, and what did they form?
intense volcanic activity released gases that formed the earths early atmosphere and water vapour.
what condensed to form the worlds oceans?
water vapour.
what other atmospheres was earths' similar to and why?
mars & venus - they consisted of mainly co2 with little to no oxygen.
give one example of a gas produced by volcanoes
nitrogen- this gradually built up in the atmosphere
small proportions of methane and ammonia
what happened to co2 when oceans formed?
it dissolved in the water and got locked up in sedimentary rocks- reducing the amount in the atmosphere
what produced the oxygen now in the atmosphere and how?
algae and plants via photosynthesis
what is the equation for photosynthesis?
6CO2 + 6H2O + -> C6H12O6 + 6O2
what is the word equation for photosynthesis?
carbon dioxide + water ->glucose + oxygen
when did algae first begin to produce oxygen?
2.7 billion years ago.
how did the evolution of plants help animals?
since plants began to evolve, the percentage of oxygen gradually increased to a level that enabled animals to evolve.
how did plants/algae decrease the percentage of carbon dioxide?
photosynthesis
what is a second way that carbon dioxide decreased?
the formation of sedimentary rocks and fossil fuels that contain carbon
Explain how deposits of limestone, coal, crude oil and natural gas formed?
When the oceans formed, carbon dioxidedissolved in the water.
Dissolved CO2 went through a series of reactions to form carbonateprecipitates. When marine organisms evolved, their shells and skeletons contained calcium carbonate.
When they died, they fell to the seabed and were buried with sediment, becoming compressed over millions of years to form sedimentary rocks (limestone + coal), crudeoil and natural gas.
what are greenhouse gases?
gases that act as an insulating layer in the earths atmosphere, allowing the earth to be warm enough to supportlife.
name 3 greenhouse gases
methane
carbondioxide
watervapour
What type of radiation does the Sun emit that hits the Earth's surface?