4.9.1 The composition and evolution of the Earth's atmosphere Flashcards
What are the main components of the Earth’s atmosphere?
About four-fifths (approximately 80%) nitrogen and about one-fifth (approximately 20%) oxygen, with small proportions of various other gases.
What was the composition of the Earth’s early atmosphere?
The early atmosphere may have consisted mainly of carbon dioxide with little or no oxygen gas, similar to Mars and Venus today.
How did volcanic activity influence the early atmosphere?
Intense volcanic activity released gases that formed the early atmosphere and produced nitrogen, methane, and ammonia.
What role did oceans play in the early atmosphere?
When oceans formed, carbon dioxide dissolved in the water, reducing its amount in the atmosphere.
How did oxygen levels in the atmosphere increase?
Oxygen was produced by algae and plants through photosynthesis, starting about 2.7 billion years ago.
What processes decreased carbon dioxide levels in the atmosphere?
Carbon dioxide levels decreased due to photosynthesis by algae and plants, and the formation of sedimentary rocks and fossil fuels.
What should students be able to describe regarding atmospheric changes?
Students should describe the main changes in the atmosphere over time and the likely causes of these changes.
What should students explain about fossil fuel formation?
Students should explain the formation of deposits of limestone, coal, crude oil, and natural gas.
