Chemistry of the Atmosphere

• how has the proportion of gases in the atmosphere changed in the last 200 million years?


  it has stayed the same
• what is the composition of the atmosphere today?

  • 80% nitrogen

  
  

  • 20% oxygen

  
  

  • small proportions of other gases (carbon dioxide, water vapour, trace quantities of the noble gases)
• why is evidence for the early atmosphere limited?

  because it happened 4.6 billion years ago
• what are the phases from one of the theories of how the atmosphere evolved?

  • phase 1: volcanoes gave out gases

  
  

  • phase 2: oceans, algae and green plants absorbed carbon dioxide

  
  

  • phase 3: green plants and algae produced oxygen
• what is phase 1 of the theory of earth's early atmosphere?

  • first billion years of Earth's history, th surface was covered in volcanoes
  • they erupted and released lots of gases
  • mostly carbon dioxide (virtually no oxygen)
  • also released nitrogen, water vapour, small amounts of methane and ammonia
• what covered the Earth's surface for the first billion years of Earth's history?

  volcanoes
• what was the early atmosphere made up of?

  • mostly carbon dioxide
  • nitrogen
  • water vapour
  • small amounts of methane and ammonia
  • virtually no oxygen
• what is phase 2 of the theory of earth's early atmosphere?

  • when the water vapour condensed, it formed oceans
  • lots of carbon dioxide was removed as it dissolved in the oceans
  • dissolved carbon dioxide went through a series of reactions to form carbonate precipitates that formed sediments on the seabed
• what happened when the water vapour in the atmosphere condensed?

  it formed the oceans
• what is phase 3 of the theory of earth's early atmosphere?
• how did oxygen increase in the atmosphere?
• how was lots of carbon dioxide removed from the early atmosphere?

  • it dissolved in the oceans
  • went through a series of reactions to form carbonate preicpitates
  • which formed sediments on the seabed
• how did green plants and algae help remove carbon dioxide from the atmosphere?

  • they evolved and absorbed some of the carbon dioxide
  • so that they could carry out photosynthesis
• what did marine animal's shells and skeletons contain after evolving?

  carbonates from the oceans
• what happened to the carbon in marine animal's shells after they died?

  it became locked up in rocks and fossil fuels
• what happens when plants, plankton and marine animals die?

  • they fall to the seabed and get buried by layers of sediment

  
  

  • this traps the carbon within them and helps to keep carbon dioxide levels in the atmosphere reduced
• what happens to the buried plants, plankton and marine animals over millions of years?

  they become compressed and form sedimentary rocks, oil and gas
• how is the process where plants, marine animals and plankton become sedimentary rocks, oil and gas useful?

  • it traps the carbon within them
  • which helps to keep carbon dioxide levels in the atmosphere reduced
• what are some fossil fuels?

  • coal
  • crude oil
  • natural gas
• how are crude oil and natural gas formed?

  • from the deposits of plankon
  • from resevoirs under the seabed
  • when they get trapped in rocks
• what is coal?


  a sedimentary rock made from thick plant deposits
• what is limestone?


  • a sedimentary rock
  • mostly made of calcium carbonate deposits
  • from the shells and skeletons of marine organisms
• what is photosynthesis?


  when plants use light to convert carbon dioxide and water into sugars
• how was oxygen produced in the atmosphere?
• what evolved first algae or green plants?


  algae
• how long ago did algae evolve?

  1. 7 billion years ago
• what happened as oxygen levels built up in the atmosphere over time?

  more complex life could evolve (like animals)
• when did the atmosphere reach a composition similar to what it is today?

  200 million years ago
• what do greenhouse gases in the atmosphere do?

  • act like an insulating layer in the Earth's atmosphere
  • which allows the Earth to be warm enough to support life
• what radiation from the sun do greenhouse gases absorb?

  long wavelength radiation that gets reflected back off the Earth
• what do greenhouse gases do after absorbing long wavelength radiation?

  • they reradiate it in all directions (including back towards the Earth)
  • resulting in warming of the surface of the Earth
• what are examples of greenhouse gases?

  • carbon dioxide
  • water vapour
  • methane
• how does the greenhouse effect work?

  • radiation from the sun passes through the Earth's atmosphere
  • Earth absorbs some radiation and warms up

  some heat is radiated from the Earth as infrared

  • some is absorbed by greenhouse gases in the atmosphere
  • atmosphere warms up leading to greenhouse effect and global warming
• what are some human activities that affect the amount of greenhouse gases in the atmosphere?

  • deforestation
  • burning fossil fuels
  • agriculture
  • creating waste
• how does deforestation lead to an increase in greenhouse gases in the atmosphere?


  fewer trees means less carbon dioxide is removed from the atmosphere via photosynthesisSee an expert-written answer!We have an expert-written solution to this problem!
• how does burning fossil fuels lead to an increase in greenhouse gases in the atmosphere?


  carbon that was 'locked up' in these fuels is released as carbon dioxideSee an expert-written answer!We have an expert-written solution to this problem!
• how does agriculture lead to an increase in greenhouse gases in the atmosphere?

  more farm animals produce more methane through their digestive processes
• how does creating waste lead to an increase in greenhouse gases in the atmosphere?

  • more landfill sites and more waste from agriculture
  • means more carbon dioxide and methane released by decomposition of waste
• what do scientists believe extra carbon dioxide from human activities is causing?

  • increase in average temperature of the Earth's surface
  • leading to climate change
• how do scientists know that human activity is leading climate change?

  • evidence for this has been peer reviewed
  • so we know it is reliable