C13 The Earth's Atmosphere Flashcards
Where is Earth’s atmosphere?
Earth’s atmosphere extends from the Earth’s surface to an altitude of approximately 10,000 km
Earth’s atmosphere today
For 200 million years, the proportions of gases in the atmosphere have been about the same as they are today:
- About 80% nitrogen
- About 20% oxygen
- Small proportions of other gases which include carbon dioxide, argon and water vapour
Why are we not certain what the Earth’s early atmosphere was like?
The Earth is 4.6 billion years old - a very long timescale - so there is a lack of evidence
Volcanic Activity Theory for the Origin of the Atmosphere
- This theory suggests that intense volcanic activity released carbon dioxide and water vapour which formed the early atmosphere
- Volcanoes also released the water vapour that condensed to form the oceans
- When the oceans formed, carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere
- Volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia
Describe how oxygen increased
Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis
- Algae first produced oxygen by photosynthesis
- Soon after, this oxygen appeared in the atmosphere
- Over the next billion years, plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve
Describe how carbon dioxide decreased
- Plant and algae photosynthesis produced oxygen and used up carbon dioxide from the atmosphere
- Carbon dioxide was also removed from the atmosphere as it was used to form sedimentary rocks and fossil fuels that contain carbon
How was coal formed
- Plants and trees used carbon dioxide during photosynthesis to build their tissues
- Plants and trees died in swamps and decayed in the absence of oxygen
- They were compressed over time to produce coal
Describe how methane decreased
- Methane reacted with the oxygen that was being produced by photosynthesis
- This produced more carbon dioxide
Methane + oxygen = carbon dioxide
+ water
Describe how ammonia decreased
- Ammonia reacted with the oxygen that was being produced by photosynthesis
- This produced more nitrogen
Ammonia + oxygen = nitrogen + water
Describe how nitrogen increased
Nitrogen gas is very un-reactive so was able to build up in the atmosphere
What is ‘locked up carbon’?
Carbon from Earth’s early atmosphere now trapped in rocks and fossil fuels
Which were the first organisms to produce oxygen on Earth?
Algae/photosynthetic bacteria
How did oil and natural gas form?
- Crude oil and natural gas were formed from the remains of plankton deposited in muds on the seabed
- These remains were covered by sediments that became layers of rock when compressed over millions of years
- The crude oil and natural gas formed is found trapped beneath these layers of rock
In the EM spectrum, what is the relationship between wavelength and amount of energy transferred?
Longer wavelengths transfer less energy
The greenhouse effect on Earth
- The Earth has a layer of gases around it: carbon dioxide, methane and water vapour
- Without the greenhouse effect, Earth would be too cold to support life
- Humans are increasing the levels of greenhouse gases in the atmosphere, which is warming the Earth too much
What are the three greenhouse gases?
Carbon dioxide, methane, and water vapour
Which type of wavelength transfers the most energy?
Short
What two things can happen to the infrared waves that reach Earth?
Reflected or absorbed