5.9.1.2 The Earth’s Early Atmosphere

Question 1

Why is evidence for the early atmosphere limited?

Answer 1

• time scale of 4.6 billion years
• theories have changed/developed

Question 2

What does one theory suggest about the Earth’s existence during the first billion years?

Answer 2

• intense volcanic activity that released gases that formed the early atmosphere

Question 3

What was the Earth’s atmosphere like at the start of its existence?

Answer 3

• similar to Mars and Venus today; mainly carbon dioxide with little to no oxygen

Question 4

What did volcanoes produce?

Answer 4

• nitrogen, which gradually built up in the atmosphere

Question 5

What other gases may have been present in small proportions?

Answer 5

• methane
• ammonia

Question 6

What did condensed water vapour form?

Answer 6

• oceans

Question 7

How was the amount of carbon dioxide removed from the atmosphere in the past?

Answer 7

• it dissolved in water
• carbonates were precipitated, producing sediments
• so reducing the amount in the atmosphere