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?

  The Earth 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 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
• What happened to the carbon in algae and plants after they died?

  They became buried and formed sedimentary rock
• What is the result of photosynthesis in terms of atmospheric gases?

  It takes in CO2 and produces oxygen
• What types of fossil fuels are formed from dead plankton?

  Crude oil and natural gas
• What is coal primarily made from?

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

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

  1. Intense volcanic activity produced CO2 and other gases.
  2. Water vapor condensed to form oceans.
  3. Algae and green plants evolved and photosynthesized.
  4. CO2 levels decreased while oxygen levels increased.
  5. Sedimentary rock and fossil fuels formed from dead organisms.
• 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 current composition of the Earth's atmosphere?

  Mostly oxygen and nitrogen
• How did the evolution of plants and algae contribute to complex life forms?

  Increased oxygen levels allowed complex life to evolve
• What is the time frame for the evolution of the Earth's atmosphere?

  4.6 billion years
• How did the early atmosphere of Earth compare to that of Mars and Venus?

  It was mostly carbon dioxide like theirs