C14- The Earths Atmosphere Flashcards
What is the atmosphere?
A layer of gases surrounding the Earth
What was the early atmosphere composed of?
Mostly carbon dioxide- from volcanoes
Very little oxygen
Nitrogen- from volcanoes
Water vapour- volcanoes
What other gases were in the early atmosphere?
Ammonia and methane
How did the oceans form?
Water vapour condensing as the Earth cooled
How did the amount of carbon dioxide in the atmosphere decrease to today’s levels?
Dissolved in the oceans
Photosynthesis
Converted into fossil fuels
Precipitates in the ocean as solid carbonates, forming sedimentary rock
When did life start to appear?
2.7 billion years ago
What was the impact of life on earth to oxygen levels?
Atmospheric oxygen increased due to photosynthesis
What happened to nitrogen levels ?
Increased slowly as nitrogen is very stable, so any process that produces it causes the overall amount to build up
Why are scientists unsure of the composition of the early atmosphere?
There is limited evidence and it was billions of years ago
What is the current composition of the earths atmosphere?
80% nitrogen
20% oxygen
Small amounts of carbon dioxide, water vapour and noble gases
What is a greenhouse gas?
A gas that traps radiation in the atmosphere
What type of radiation do greenhouse gases absorb?
Long wavelength radiation
What are the main three greenhouse gases?
Carbon dioxide, methane, water vapour
Give the ways human activities has increased atmospheric carbon dioxide levels?
Burning of fossil fuels
Deforestation
Give the ways human activities has increased atmospheric methane levels?
Cattle farming
Rice farming
