C13 - The Earth's Atmosphere Flashcards
What are the proportions of gases in the atmosphere today?
80% Nitrogen
20% Oxygen
Small proportions of other gases:
- Carbon Dioxide
- Water Vapour
Why are scientists not certain of what the Earth’s early atmosphere was like?
The Earth is 4.6 billion years old - there is a lack of evidence.
What is the name of the theory behind the origin of the Earth’s early atmosphere?
The Volcanic Activity Theory for the Origin of the Atmosphere
What gases were released during the first billion years of the Earth’s existence?
Due to the intense volcanic activity, CO2 and H2O were the main gases released.
How did the oceans form?
Volcanoes released water vapour that condensed to form the oceans.
What 2 planets was the Earth’s early atmosphere most like?
Mars and Venus - mainly CO2 and little to no Oxygen.
What other gases made up the early atmosphere in smaller proportions?
Nitrogen, Methane and Ammonia
How did the levels of CO2 in the atmosphere begin to decrease?
- CO2 dissolved into the newly formed oceans.
- CO2 used up in plant and algae photosynthesis.
- CO2 also used in producing sedimentary rocks (limestone - CaCO3)
Why did the Oxygen levels begin to increase?
Plants and algae began to photosynthesise, which produced and increased the demand for Oxygen.
Why did Methane and Ammonia levels decrease?
They got used up as they reacted with the oxygen produced by photosynthesis.
Why did Nitrogen levels increase?
Nitrogen is unreactive so was able to accumulate in the atmosphere.
What 2 sedimentary rocks were formed as the atmosphere evolved?
1) Limestone - CaCO3
2) Coal
How did Limestone form?
- CO2 dissolved in oceans to form Carbonate ions.
- Carbonate ions used by marine organisms to build shells/skeletons out of calcium carbonate.
- Upon death, the shells/skeletons sunk.
- Shells/skeletons buried and compressed over millions of years to form limestone.
How did Coal form?
- Plants and trees died in swamps and decayed in the absence of oxygen.
- Compressed over millions of years to form Coal.
How did Crude Oil and Natural gas form?
- Formed from the ancient biomass of plankton buried in mud.
- Remains of plankton covered by more sediment.
- Compressed over millions of years to from Crude Oil and Natural Gas
Temperature during burial/compression determines whether oil/gas produced.
Why has the amount of CO2 in the atmosphere remained fairly constant in the last 200 million years?
The Carbon Cycle
What is the major source of atmospheric pollutants?
Combustion of fuels (mostly hydrocarbons).
What do most fuels contain?
Carbon, Hydrogen and some traces of Sulfur.
What are the 6 major atmospheric pollutants?
1) Carbon Dioxide, CO2
2) Water Vapour, H2O
3) Carbon Monoxide, CO
4) Sulfur Dioxide, SO2
5) Nitrogen Oxides, NOx
6) Solid Particulates / Unburned Fuel
How are Carbon Dioxide and Water Vapour produced industrially?
They are produced by the complete combustion of hydrocarbon fuels.
E.g Methane: CH4 + O2 —> CO2 + H2O
What are the effects of Carbon Dioxide in the atmosphere?
- Main greenhouse gas.
- Enhances greenhouse effect and causes global warming/climate change.
What are the effects of water vapour in the atmosphere?
None.
How can CO2 in the atmosphere be reduced?
Burning less fossil fuels/hydrocarbon fuels.
How is Carbon Monoxide produced?
Produced by the incomplete combustion of hydrocarbon fuels (insufficient oxygen).
