The composition and evolution of the Earth's atmosphere：練習題

• a.

  0.04%

• b.

  20%

• c.

  50%

• d.

  80%

• a.

  4.6 billion years ago

• b.

  10,000 years ago

• c.

  200 million years ago

• d.

  2.7 billion years ago

• a.

  Mainly \(CO_{2}\) released by volcanoes \(\rightarrow\) decrease in \(CO_{2}\) by dissolution in oceans and photosynthesis \(\rightarrow\) increase in \(O_{2}\) by plants.

• b.

  Mainly \(N_{2}\) released by oceans \(\rightarrow\) increase in \(CO_{2}\) by respiration \(\rightarrow\) decrease in \(O_{2}\) by combustion.

• c.

  Mainly \(O_{2}\) released by volcanoes \(\rightarrow\) increase in \(N_{2}\) by photosynthesis \(\rightarrow\) decrease in \(CO_{2}\) by freezing.

• d.

  Equal parts \(O_{2}\) and \(N_{2}\) from the start \(\rightarrow\) increase in greenhouse gases by industrialisation \(\rightarrow\) loss of atmosphere to space.

• a.

  Volcanic eruptions

• b.

  The formation of sedimentary rocks

• c.

  Photosynthesis by algae and plants

• d.

  Condensation of water vapour

• a.

  By the formation of sedimentary rocks like limestone.

• b.

  By the process of photosynthesis in plants.

• c.

  By the intense volcanic activity during the first billion years.

• d.

  By the formation of fossil fuels containing carbon.

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