Evolution of the atmosphere

• What is the composition of the Earth's atmosphere?

  About 80% nitrogen and 20% oxygen
• What gases make up less than one percent of the Earth's atmosphere?

  Carbon dioxide, water vapor, noble gases
• What role did volcanic activity play in the early atmosphere?

  It created a carbon dioxide-rich atmosphere
• How did algae and plants affect atmospheric composition?

  They reduced CO2 and increased oxygen levels
• What is the current status of the theory regarding atmospheric evolution?

  It is supported by evidence but remains a theory
• How long has the Earth been evolving its atmosphere?

  About 4.6 billion years
• What was the state of the Earth during its first billion years?

  It was dry with intense volcanic activity
• What gases were produced by volcanic activity in the early atmosphere?

  Carbon dioxide, water vapor, nitrogen, methane, ammonia
• What happened to carbon dioxide as water vapor condensed?

  It dissolved in the oceans
• What did the dissolved carbon dioxide in oceans form?

  Carbon precipitates and sediments
• When did algae begin to appear in Earth's history?

  About 2.7 billion years ago
• What process do algae and green plants use to produce oxygen?

  Photosynthesis
• How did the evolution of algae and plants impact life on Earth?

  Allowed more complex life like animals to evolve
• What happens to algae and green plants when they die?

  They become buried in sediment
• What do sedimentary rocks and fossil fuels trap?

  Carbon from dead organisms
• What determines the type of substance formed from buried organisms?

  The type of organism and conditions involved
• What is crude oil mainly formed from?

  Dead plankton
• What is coal made from?

  Thick deposits of dead plant material
• What is limestone primarily made of?

  Calcium carbonate from marine organisms
• What are the key stages in the evolution of the Earth's atmosphere?

  1. Intense volcanic activity produced CO2 and other gases.
  2. Water vapor condensed to form oceans, dissolving CO2.
  3. Algae and green plants evolved, reducing CO2 and increasing oxygen.
  4. Sedimentary rocks and fossil fuels formed from buried organisms.
• What is the current composition of the Earth's atmosphere?

  Mostly oxygen and nitrogen
• What is the significance of sedimentary rock and fossil fuels in relation to the atmosphere?

  They trap carbon and prevent it from re-entering
• What is the total time span of Earth's atmospheric evolution?

  4.6 billion years