Chemistry of the Atmosphere Flashcards
Why is evidence for Earth’s early atmosphere limited
Time scale is 4.6 billion years
Phases of evolution of atmosphere
- phase 1 - volcanoes
- phase 2 - carbon dioxide absorption
- phase 3 - oxygen release
Evolution of atmosphere PHASE 1
- first billion years of Earth - surface covered in volcanoes
- erupted and released many gases - forming the atmosphere
- early atmosphere mostly carbon dioxide, virtually no oxygen (like Mars + Venus now)
- volcanoes also released nitrogen, water vapour, small amounts of methane + ammonia
Evolution of atmosphere PHASE 2
- water vapour in atmosphere condensed - formed oceans
- lots of carbon dioxide dissolved in oceans - carbonates were precipitated, producing sediments
- green plants + algae absorbed some carbon dioxide for photosynthesis
Evolution of atmosphere PHASE 3
- 2.7 billion years ago - algae evolved to photosynthesise
- next billion years - green plants evolved
- oxygen levels build up, more complex life (animals) could evolve
Composition of Earth’s atmosphere
- approx 78% nitrogen
- approx 21% oxygen
- <1% other gases - mainly carbon dioxide, noble gases, water vapour
How long have proportions of gases in atmosphere been roughly same as today
200 million years
How is carbon dioxide reduced through trapping carbon
- plants + plankton + marine animals die
- fall to seabed
- buried by layers of sediment
- become compressed to form sedimentary rocks + oil + gas
- carbon trapped within them
Coal
Sedimentary rock made from thick plant deposits
Limestone
Sedimentary rock mostly made of calcium carbonate deposits from shells + skeletons of living organsisms
Greenhouse gases
- carbon dioxide
- methane
- water vapour
Function of greenhouse gases
Maintain temperatures on Earth high enough to support life
Greenhouse effect
- sun emits short wavelength UV radiation
- reflected back off Earth as long wavelength radiation
- absorbed by greenhouse gases
- re-emitted as infrared radiation in all directions, including towards Earth
- warms Earth
What can affect amount of greenhouse gases in atmosphere
- deforestation
- burning fossil fuels
- agriculture
- creating waste
How does deforestation affect amount of greenhouse gases in atmosphere
Fewer trees mean less carbon dioxide removed from atmosphere via photosynthesis
How does burning fossil fuels affect amount of greenhouse gases in atmosphere
Carbon ‘locked up’ in the fuels released into atmosphere as carbon dioxide
How does agriculture affect amount of greenhouse gases in atmosphere
More farm animals produce more methane through digestive processes
How does creating waste affect amount of greenhouse gases in atmosphere
More landfill sites + more agricultural waste means more carbon dioxide + methane released by decomposition of waste
What is causing increase in Earth’s average surface temperature
Extra carbon dioxide from human activity (evidence for this has been peer reviewed)
Problem with Earth’s average surface temperature increasing
Will lead to global climate change
Problem with complications of climate change
- difficult to model global climate change - too complex
- leads to oversimplified models
- speculation + opinions presented in media may be based on only parts of evidence - may be biased
Consequences of climate change
- polar ice caps melting
- changes in rainfall patterns
- increasing frequency/severity of storms
- changes in temp + amount of water in habitats
What happens when polar ice caps melt
- sea levels rise
- causing increased flooding in coastal areas + coastal erosion
What happens if rainfall patterns change
- amount, timing, distribution can change
- some regions get too much/little water
- can affect ability for certain reasons to produce food
