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 theory about the evolution of the atmosphere?

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

  About 4.6 billion years
• What characterized the Earth's atmosphere in the first billion years?

  It was dry with intense volcanic activity
• What gases were produced by volcanic activity?

  Carbon dioxide, water vapor, nitrogen, methane, ammonia
• 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 is the result of photosynthesis in terms of atmospheric gases?

  It takes in CO2 and produces oxygen
• What happened as water vapor condensed in the early atmosphere?

  It formed oceans and dissolved CO2
• What happened to carbon in algae and green plants after they died?

  They became buried and formed sedimentary rock
• 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 changes in Earth's atmosphere over billions of years?

  • First billion years: Volcanic activity produced CO2
  • Formation of oceans from condensed water vapor
  • Algae and plants evolved, reducing CO2 and increasing oxygen
  • Burial of organic matter formed sedimentary rock and fossil fuels
• What is the current state of the Earth's atmosphere?

  It is mostly nitrogen and oxygen
• What happens to carbon trapped in sedimentary rock and fossil fuels?

  It prevents carbon from re-entering the atmosphere
• What is the significance of the evolution of algae and green plants?

  They allowed more complex life to evolve
• What is the main takeaway from the video about Earth's atmosphere?

  It evolved from volcanic activity and photosynthesis