The Earths Sea And Atmosphere Flashcards
What is phase one of the evolution of the early atmosphere
The earths surface was originally molten so it was so hot any atmosphere just boiled away
Eventually when it cooled down a thin crust formed but volcanoes kept erupting
They gave out lots of gas including carbon dioxide and water vapour
So the early atmosphere was probably mostly co2
And hardly any oxygen much like the atmospheres of Venus and mars today
What happened when the atmosphere cooled
The atmosphere condensed forming oceans and the carbon dioxide dissolved into the oceans
What is the composition of the atmosphere now
78% nitrogen
21% oxygen
1% argon
0.04% carbon dioxide
What happens in phase two of the evolution of the earths atmosphere
Lots of co2 was dissolved into the oceans
Marine organisms developed which took some of the co2 out of the oceans
When the organisms died they were buried under layers of sediment and the co2 was trapped in the layers
Green plants golfed over most of the earth and they were happy with the co2 atmosphere because they could do photosynthesis
They also released oxygen into the Atmosphere so the oxygen levels increased
What happened in phase 3 of the evolution if the atmosphere
The build up of oxygen killed off some of the earliest organisms but allowed more complex ones to develop
The oxygen created an ozone layer which blocked out some of the suns heat allowing more organisms to develop
There is very little co2 left now
How is human activity changing the atmosphere
Burning fossil fuels releases co2 e.g. In fossil fuels in power stations or car engines
Deforestation means that Trees that would take in co2 from the atmosphere are not there to take any in
Livestock farming releases lots of methane into the atmosphere
How is volcanic activity changing the atmosphere
Sulfur dioxide can b thrown high up into the atmosphere when volcanoes erupt
It reacts with sunlight water and oxygen to form volcanic smog
Carbon dioxide is also released by volcanic eruptions
How are Antarctic ice cores used to see changes in the atoms
We can find out from Antarctic ice cores because each year a new layer of ice forms trapping bubbles of air so the deeper the ice the older the air so we can look at the bubbles to see how the air has changed but it has to be really precise because the changes between layers can be very tiny
Why are sources of information on the early atmosphere limited
No one was actually there and it’s hard to find precise methods to see the changes
How can you investigate the proportion of gas in the early atmosphere
When heated copper reacts with oxygen in the air to copper oxide so the reaction uses up oxygen
If you heat excess oxygen in a tube and pass air over it using two syringes and you can tell how much oxygen has been used up by the markers on the syringe
2Cu+O2-> 2CuO
