The Earth`s Sea And Atmosphere

Question 1

how was the earth’s first atmosphere formed? what did it contain?

Answer 1

formed by gases produced by volcanic activity, it contained: a little or no oxygen, a large amount of carbon dioxide, water vapour and small amounts of other gases

Question 2

why is it difficult to be precise about the evolution of the atmosphere?

Answer 2

there are different sources of information, but not all evidence leads to the same conclusion (they tell us different things)

Question 3

how were the oceans formed?

Answer 3

the earth cooled and this caused water vapour to condense.

Question 4

how was the amount of carbon dioxide reduced in the atmosphere?

Answer 4

1) carbon dioxide dissolved in the oceans

2) marine organisms used the carbon dioxide to make calcium carbonate for shells

Question 5

how was oxygen produced?

Answer 5

green plants evolved over most of the earth. they removed carbon dioxide from the air and produced oxygen by photosynthesis. this caused the oxygen levels to gradually increase.

Question 6

what is the current composition of the atmosphere

Answer 6

large amounts of nitrogen(78%), oxygen(21%), argon(0.9%), carbon dioxide(0.04%), small amounts of other gases.

Question 7

how can small changes in the atmosphere occur

Answer 7

1) burning fossil fuels releases carbon dioxide into the atmosphere. sulfur dioxide can also be released from burning coal
2) farming affects the atmosphere, as cattle and rice fields release methane
3) deforestation adds carbon dioxide to the atmosphere. volcanoes emit sulfur dioxide and carbon dioxide when they erupt.
4) volcanic activity emits sulfur dioxide and carbon dioxide when they erupt.