8.2 Earth and Atmospheric Science
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Earth’s early atmosphere
Mostly carbon dioxide and water vapour and some methane and ammonia
What was the atmosphere when Earth was molten
There was no atmosphere
How were the first atmospheric gases released
After the molten Earth, it cooled and a thin crust formed, but volcanoes kept erupting releasing gases from inside the Earth
How did the atmosphere lose its water vapour
It condensed to form the oceans
How did the atmosphere lose most of its carbon dioxide
-A lot dissolved into the oceans -Used for photosynthesis by early plants -Got locked up in fossil fuels and sedimentary rocks
How was nitrogen released into the atmosphere
-Formed from ammonia reacting with water -Released by denitrifying bacteria
Why didn’t the amount of nitrogen in the atmosphere decrease
It isn’t very reactive, so it was made but not broken down
How did the atmosphere gain its oxygen
It was produced by early photosynthesising plants
How did oxygen affect the Earth’s organisms
-Killed off early organisms that couldn’t tolerate it -Allowed the evolution of more complex organisms that used the oxygen -Created the ozone layer which blocked harmful rays and enabled more complex organisms to evolve
Percentage of nitrogen in today’s atmosphere
78%
Percentage of oxygen in today’s atmosphere
21%
Test for oxygen
Check if the gas will relight a glowing splint
Greenhouse gas examples
-Carbon dioxide -Methane -Water vapour
The greenhouse effect
1- The sun emits short wavelength EM radiation which passes through the Earth’s atmosphere as it isn’t absorbed by greenhouse gases 2- When this reaches the surface it is absorbed and re-emitted as long wavelength IR radiation 3- This is absorbed and re-radiated in all directions by greenhouse gases in the atmosphere 4- The IR radiation re-radiated towards Earth is thermal radiation so it warms the surface
Enhanced greenhouse effect
When the concentration of greenhouse gases in the atmosphere increases so more long wavelength radiation is absorbed and re-radiated
Why is the amount of carbon dioxide released increasing
-There is a higher energy consumption so more fossil fuels are burnt -Deforestation means there are less plants removing carbon dioxide from the atmosphere
Why has the energy consumption increased
-The human population has increased -Change in lifestyle means that the each person is using more energy (for cars or plane travel etc)
What causes deforestation
The population has increased so humans need more space to build houses and grow food so trees are chopped down
Why is the amount of methane in the atmosphere increasing
It is produced by the digestive processes of livestock and more humans means that we are farming more livestock
There is not a high concentration of methane in the atmosphere. Why is methane such a big problem then
It is a very effective greenhouse gas
Example of non-human activity today releasing carbon dioxide into the atmosphere
Volcanoes erupting
Why is the temperature increasing
The amount of carbon dioxide and methane in the atmosphere is increasing causing an enhanced greenhouse effect
Global warming
The global temperature is increasing because of the enhanced greenhouse effect
Effects of climate change
-Global warming -Flooding