The Atmosphere

Question 1

When did the Earth form?

Answer 1

-approximately 4.6 billion years ago

Question 2

Why can’t scientists be certain about the Earth’s early atmosphere?

Answer 2

-not enough direct evidence

-theories change as new discoveries are made

Question 3

Where did Earth’s early atmosphere come from?

Answer 3

-intense volcanic activity released gases, including carbon dioxide, nitrogen, water vapour, ammonia, and methane

Question 4

What were the main gases in the early atmosphere?

Answer 4

-large amount of carbon dioxide, little or no oxygen, and small amounts of ammonia and methane

Question 5

How did oceans form on Earth?

Answer 5

-water vapour from volcanoes condensed as Earth cooled, leading to ocean formation

Question 6

How did nitrogen build up in the atmosphere?

Answer 6

-released by volcanic activity, nitrogen stayed in the atmosphere because it is unreactive

Question 7

How was Earth’s early atmosphere similar to Mars and Venus?

Answer 7

-had high levels of carbon dioxide and little or no oxygen, like those planets today

Question 8

How did the formation of oceans affect carbon dioxide levels in the atmosphere?

Answer 8

-carbon dioxide dissolves readily in water

-it dissolved in the ocean to form soluble carbonate compounds

-reducing its levels in the atmosphere

Question 9

How were carbonate compounds removed from the oceans?

Answer 9

-were precipitated as sedimentary rocks, such as limestone

Question 10

How did photosynthesis affect carbon dioxide levels?

Answer 10

-early plants and algae absorbed carbon dioxide
-from the oceans during photosynthesis
-reducing atmospheric levels.

Question 11

How did fossil fuels form from early organisms?

Answer 11

-dead plants and animals were buried under sediments

-over millions of years heat and pressure

-turned them into crude oil, coal, and natural gas

Question 12

Why didn’t the remains of organisms oxidise when forming fossil fuels?

Answer 12

-were buried in sediments where there was a lack of oxygen, preventing oxidation

Question 13

How is natural gas related to crude oil?

Answer 13

-it’s often found on top of crude oil, trapped under sedimentary rock

Question 14

State two reasons why the amount of carbon dioxide in the atmosphere decreased over time

Answer 14

-carbon dioxide dissolved in the oceans
-primitive plants/algae used it for photosynthesis