Earths Atmosphere

• What is the atmosphere?


  a layer of gas surrounding the Earth
• What was the early atmosphere composed of?


  mostly carbon dioxide
• 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 to fossil fuels, precipitated as insoluble metal carbonates
• When did life start to appear, and what was the impact of this on oxygen in the atmosphere?

  about 2.7 billion years ago; amount of atmospheric oxygen increased as it was released in photosynthesis
• about 2.7 billion years ago; amount of atmospheric oxygen increased as it was released in photosynthesis


  increased slowly as it is a very stable molecule
• Why can scientists not be sure about the composition of the Earth’s early atmosphere?


  it was billions of years ago and evidence is limited
• What is the current composition of the atmosphere?


  approximately 80% nitrogen, 20% oxygen, and trace amounts of other gases such as carbon dioxide, water vapour, and noble gases
• What is a greenhouse gas?


  a gas that traps radiation from the Sun
• What type of radiation do greenhouse gases absorb?


  longer wavelength infrared radiation
• Name three greenhouse gases

  .

  methane, carbon dioxide, water vapour
• Give two ways recent human activities have increased the amount of atmospheric carbon dioxide.


  burning fossil fuels, deforestation
• Give two ways recent human activities have increased the amount of atmospheric methane


  rice farming, cattle farming
• What is global warming?

  an increase in the overall global average temperature
• What is global climate change?

  the change in long-term weather patterns across the planet
• What are some possible effects of climate change?

  sea levels rising, extreme weather events, changes in the amount and time of rainfall, changes to ecosystems and habitats, polar ice caps melting
• What is a carbon footprint?


  the amount of carbon a product, process, or person releases into the atmosphere over its lifetime
• How is carbon monoxide formed, and what is the danger associated with it?


  incomplete combustion; colourless and odourless toxic gas
• How are particulates formed, and what are the dangers associated with them?


  incomplete combustion; global dimming, respiratory problems, potential to cause cancer
• How is sulfur dioxide formed, and what are the dangers associated with it?

  sulfur impurities in fossil fuels react with oxygen during combustion; acid rain, respiratory problems
• How are oxides of nitrogen formed, and what are the dangers associated with them?


  atmospheric oxygen and nitrogen react in the heat of a combustion engine; acid rain, respiratory problems