The Earth's Atmosphere

Question 1

Rank the gases in the present-day atmosphere (200 million years until now) from the highest percentage to lowest:
1.
2.
3.
4.

Answer 1

1. Nitrogen.
2. Oxygen.
3. Carbon dioxide.
4. Other gases.

Question 2

During the first billion years, there was intense ____________________.

Volcanoes __________________ that formed into the __________________.

Answer 2

volcanic activity

released gases
atmosphere

Question 3

Volcanoes released water vapour.

As the ______________, the water vapour _____________________________.

Answer 3

Earth cooled
condensed to form the oceans

Question 4

Volcanoes released huge amounts of ____________________.

So in the early stages, the Earth mainly consisted of __________________ with very little ____________________________.

Answer 4

carbon dioxide

carbon dioxide
nitrogen and oxygen

Question 5

Volcanoes released nitrogen which ___________________ in the atmosphere because nitrogen is _______________.

Answer 5

gradually built up
unreactive

Question 6

In the early stages, volcanoes released small amounts of other gases such as ____________ and _____________.

Answer 6

methane
ammonia

Question 7

From 200 million years ago to present day,
carbon dioxide levels ______________.
oxygen levels ______________.
nitrogen levels ______________.

Answer 7

decreased
increased
increased

Question 8

When water vapour condensed into oceans, carbon dioxide ___________________ to form a _______________ (_____________________________).

This is because carbon dioxide is a very _______________.

Answer 8

dissolved in oceans
weak acid
soluble carbonate compounds

soluble gas

Question 9

The carbonate compounds __________ with ______________ in the sea to form _______________.

Over time, forming ________________________ on the ______________.

Answer 9

reacted
minerals
precipitates

carbon rock sediment
sea bed

Question 10

Some carbon dioxide in the ocean was used to make __________ and _________________________.

When they die, the form the sedimentary rock:______________.

So carbon dioxide is ______________ from the atmosphere.

Answer 10

corals
shells of organisms

limestone

removed

Question 11

Around 2.7 billion years ago, ___________________________.

Photosynthesis ____________________ and __________________________ from the atmosphere,

Answer 11

photosynthetic algae evolved

produced oxygen
removed carbon dioxide

Question 12

Over billions of years, plants ___________.
_______________ the amount of oxygen in the atmosphere.

The level of oxygen reached the point where ____________________________.

Answer 12

evolved
Increasing

animals could evolve

Question 13

True or false: Carbon is trapped in fossil fuels.

Answer 13

True.

Question 14

What is coal formed from?

Answer 14

Remains of ferns and trees.

Question 15

Give 2 reasons why coal cannot decompose in marshy wetlands:

Answer 15

1. Lack of oxygen.
2. Acidic conditions.

Question 16

__________ cannot carry out _________________ in marshy wetlands, so plant remains are ________________________.

And under _________________ and _____________ coal is formed.

Answer 16

Bacteria
decomposition
compressed with sediment

high temperature
pressure

Question 17

What is crude oil formed from?

Answer 17

Plankton.

Question 18

When plankton _____ they settle in _____ on the sea bed.

If oxygen is not present, they __________________________ because oxidation cannot take place.

Over time, they are _______________________. __________________ converts plankton into _____________.

Answer 18

die
mud

do not decompose

compressed by sediment
Heat and pressure
crude oil

Question 19

What does natural gas mainly consist of?

Answer 19

The hydrocarbon: methane.

Question 20

What is natural gas formed from?

Answer 20

Plankton.

Question 21

Where is natural gas mainly found?

Answer 21

On top of crude oil deposits.

Question 22

All fossil fuels contain trapped carbon.

Which is part of the carbon dioxide taken in by what process?

Answer 22

Photosynthesis.

Question 23

True or false: Oxygen levels decreased due to photosynthesis of plants.

Answer 23

False. Oxygen levels increased.

Question 24

What are 2 indirect evidences of the composition of the Earth’s early atmosphere?

Answer 24

1. Composition of rocks as old as the Earth.
2. Fossilised remains of organisms alive at different times since the early atmosphere.