Earth's atmosphere Flashcards
Why was the early atmosphere mainly carbon dioxide?
Volcanoes released large amounts of carbon dioxide.
What evidence is there to suggest that was no oxygen in the early atmosphere?
Volcanoes do not release oxygen
The iron compounds found in the Earth’s oldest rocks are compounds that would only form in the absence of oxygen.
What gases do volcanoes release?
Carbon dioxide, water vapour, nitrogen, methane and ammonia.
How did the oceans form?
Volcanoes released various gases, one of which was water vapour, and when the earth cooled down, the water vapour condensed to form the oceans.
What are the two theories of how nitrogen came to be in the atmosphere?
Volcanoes released nitrogen when the earth was young - so the atmosphere has always contained a lot of nitrogen.
Most of the nitrogen was added to the atmosphere gradually due to the reactions of nitrogen - containing compounds released from volcanoes.
What is the composition of the earth’s current atmosphere?
78% nitrogen, 21% oxygen, nearly 1% argon, 0.04% carbon dioxide and trace amounts of other gases: carbon monoxide, methane, nitrogen oxides and sulcus dioxide.
Why isn’t the amount of water vapour in the atmosphere included when giving the composition of dry air?
The amount of water vapour changes from day to day due to evaporation and condensation.
How old is the earth?
Roughly 4.54 billion years old.
How was the early atmosphere created?
By volcanoes erupting and releasing gases.
Describe how the earths atmosphere has evolved.
The earths atmosphere was originally molten and any atmosphere just billed away.
- gradually the earth cooled down, and volcanoes began to erupt and release gases: mainly carbon dioxide, water vapour and also nitrogen, methane and ammonia.
- the earths atmosphere was mainly carbon dioxide and water vapour.
- as the earth cooled, the water vapour condensed and formed the oceans
- so the amount of water vapour in the atmosphere decreased.
- carbon dioxide in the atmosphere dissolved in the oceans and was turned into the shells of marine organisms (calcium carbonate)
- the carbon dioxide in the shells became locked up in carbonate rocks once the organisms had died, and became sedimentary rocks when layers of sediment buried them.
- 3 billion years ago, green plants evolved and took in carbon dioxide but released oxygen through photosynthesis. Thus lowering amount of carbon dioxide and increasing the amount of oxygen in the atmosphere.
- complex organisms evolved to tolerate the high amounts of oxygen
- oxygen created the ozone layer, which blocked harmful UV rays and allowed organisms to move onto dry land. There is now little carbon dioxide in the atmosphere.
- nitrogen was released into the atmosphere by volcanoes.
Why is our atmosphere still changing?
Human activity: Burning fossil fuels Deforestation Livestock farming Rice fields Engines and furnaces
Natural activity:
Volcanic activity
Lightning
How does burning fossil fuels change the atmosphere?
As the work is becoming more industrialised, more fossil fuels are burnt in power stations - increasing the amount of carbon dioxide, carbon monoxide and sulphur dioxide.
Carbon monoxide is released during incomplete combustion of fossil fuels.
How does deforestation change the atmosphere?
There will be fewer trees to remove carbon dioxide from the atmosphere by photosynthesis - increasing the amount of carbon dioxide.
How does livestock farming change the atmosphere?
When cattle digest their food they release methane - increasing amount of methane.
How does rice fields change the atmosphere?
They produce large amounts of methane - increasing amount of methane.
