Chemistry of the Atmosphere: Composition & Evolution of the Earth’s Atmosphere Flashcards
Describe the proportions of gases in the modern atmosphere.
- 78% nitrogen
- 21% oxygen
- > 1% carbon dioxide
- small quantities of water vapour and noble gases
Approximately how old is the Earth?
4.6 billion years old
Why can scientists not be certain about the early atmosphere?
There is no evidence as it was so long ago.
What was the Earth like during the first billion years? What impact did this have on the atmosphere?
- there was intense volcanic activity
- these volcanoes released water vapour, large amounts of carbon dioxide, nitrogen, which gradually build up in the atmosphere, and small amounts of methane and ammonia
Describe the composition of the Earth’s early atmosphere.
- mainly carbon dioxide
- small but increasing amounts of nitrogen
What are the 3 main differences between the early atmosphere and the atmosphere of the Earth today?
- much more nitrogen in the today’s atmosphere
- much less carbon dioxide in today’s atmosphere
- much more oxygen in today’s atmosphere
How were the oceans formed?
The water vapour condensed to form oceans.
What effect did the formation of the sea have on the atmosphere?
- decreased water vapour
- decreased carbon dioxide
How was the amount of carbon dioxide in the atmosphere dcreased?
This carbon dioxide reacted with minerals in the sea to form carbon precipitates which, over time, formed sediments on the sea bed.
Marine animals evolved and their shells and skeletons contained some of these carbonates from the oceans.
Plants and algae evolved absorbed some of the carbon dioxide for photosynthesis.
Some carbon was locked up in fossil fuels and rocks.
How were sediments formed?
When plankton, plants and other marine animals die, they fall to the seabed and are buried under layers of sediment.
Over millions of years, they become compressed and form sedimentary rocks, oil and gas.
How did the amount of oxygen in the atmosphere increase?
Plants and algae evolved which photosynthesised.
