SC20-21

• what was earth's early atmosphere made up of?

  mainly carbon dioxide with smaller amounts of water vapour and other gases. There was little to no oxygen.
• how did volcanoes affect earth's early atmosphere?

  they released large amount of gas such as carbon dioxide, water vapour and small amounts of other gases (including nitrogen).
• what was there a lot of on early earth that probbaly helped form its atmosphere?

  volcanoes
• what are the atmospheres of Venus and Mars mainly made up of?

  carbon dioxide, thought to be released by volcanoes.
• In context to one of Saturn's moons, Titan, what do some scientists think that early earth's atmosphere was made up of?

  nitrogen. Titan's atmosphere is 98.4% nitrogen, probably also released by volcanoes.
• what evidence is there to show that earth's early atmosphere is less likely to have been like Titan's?

  space probes have shown that Titan has an icy exterior, unlike earth.
• how long ago did the earth cool down?

  4 billion years ago
• in terms of the earth cooling down, how were oceans formed?

  the water vapour in the atmosphere cools and condenses into water to form oceans.
• in earth's early atmosphere, where did oxygen come from?

  • iron pyrite
  • microorganisms
• what happened to the earth's atmosphere over time?

  oxygen levels increased and carbon dioxide levels decreased.
• what is degassing?

  the earth's surface cooled and a thin crust formed, but volcanoes kept erupting, releasing gases from inside the earth.
• what happened to the earth as a result of degassing?

  it released mainly carbon dioxide, but also steam, methane, and ammonia.
• how was nitrogen put into the atmosphere?

  it was formed by ammonia reacting with oxygen, and was released by denitrifying bacteria.
• how did the amount of nitogen in the atmosphere increase?

  nitrogen isnt very reactive so the amount of nitrogen in the atmosphere increased, because it was being made but not broken down.
• why did the oxygen levels increase and the carbon dioxide levels decrease in earth's atmosphere?

  green plants evolved over most of the earth. As they photosynthesised, they removed carbon dioxide and produced oxygen.
• what happened to carbon dioxide as a result of green plants evolving around the earth?

  carbon dioxide levels decreased, it eventually got locked up in fossil fuels and sedimentary rocks.
• what happened as a result of the build up of oxygen in earth's atmosphere?

  it killed off early microorganisms that couldn't tolerate it.
• what did the killing off of early microorganisms allow?

  the evolution of more complex organisms that made use of the oxygen.
• what created the o-zone layer?

  the build-up of oxygen in the atmosphere.
• what did the o-zone layer do?

  blocked harmful rays from the sun and enabled even more complex organisms to evolve.
• how can you test for oxygen?

  by checking if gas will relight a glowing splint.
• what is today's atmosphere made up of?

  • 78% nitrogen
  • 21% oxygen
  • 1% other gases (carbon dioxide, water vapour, noble gases)
• what does the sun give out?

  electromagnetic radiation
• what happens to the electromagnetic radiation with short wavelenths that are emitted by the sun?

  absorbed by the earth, warming the planet.
• what happens to some electromsgnetic radiation at most wavelengths that are emitted by the sun?

  passes through the atmosphere.
• why is the greenhous gas effect important?

  it keeps the earth warm enough for humans to live on.
• what are greenhouse gases?

  the gases in the atmosphere that can absorb and reflect heat radiation. They're only present in small amounts. Carbon dioxide, water vapour, and methane are the 3 greenhouse gases.
• what happens if the concentration of greenhouse gases in the atmosphere increases?

  an enhanced greenhouse effect. This is where more heat radiation from the Earth is absorbed and less is re-emitted back into space. This causes the atmosphere to heat up.
• what keeps the earth warm?

  the greenhouse gas effect. It's the reabsorption and re-emission of IRcradiation by greenhouse gases.
• what does the increased energy consumption come from?

  mainly from the burning of fossil fuels, which released more carbon dioxide.
• as the consumption of fossil fuels increases, what else increases?

  the concentration of carbon dioxide in the atmosphere.
• a larger population means more land is needed to build houses and grow food. This space is made through what?

  chopping down trees, deforestation.
• what is carbon dioxide produced by?

  • burning fossil fuels
  • erupting volcanoes
• what was significant in the reduction of carbon dioxide in early earth's atmosphere?

  the formation of oceans
• what human activities caused the atmospheric concentrations of greenhouse gases to increase?

  • landfill sites
  • burning fossil fuels
  • agriculture
  • deforestation
• how does agriculture increase greenhouse gas concentrations in the atmosphere?

  farm animals release methane during digestion.
• how does burning fossil fuels increase greenhouse gas concentrations in the atmosphere?

  it releases carbon in the form of carbon dioxide. This carbon has been stored away for millions of years previously.
• how does land fill sites increase greenhouse gas concentrations in the atmosphere?

  The number and size of land fill sites are increasing. This means that more mounds of waste are decomposing. This process of decomposition released methane.
• how does deforestation increase greenhouse gas concentrations in the atmosphere?

  as we cut down trees, the global rate of photosynthesis will decrease. Carbon dioxide is a reactant in photosynthesis meaning less carbon dioxide will be removed from the atmosphere.
• what are the stages of the greenhouse effect?

  1. Short wavelength infrared radiation emitted by the sun enters the atmosphere and travels to the Earth's surface.
  2. The Earth absorbs a portion of this radiation, but longer wavelength radiation is reflected back into the atmosphere.
  3. Greenhouse gases absorb some reflected wavelength radiation before re-radiating it as heat energy, some of which heads back to Earth.
  4. The temperature of Earth's surface increases.