The Global Carbon Cycle

Question 1

Define carbon sink.

Answer 1

A store that absorbs more carbon than it releases.

Question 2

Define carbon source.

Answer 2

It releases more carbon than it absorbs.

Question 3

Define flux.

Answer 3

The amount of carbon held in each store is subject to change over a certain timescale.

Question 4

What are the six carbon stores?

Answer 4

• Marine sediments and sedimentary rocks
• Ocean
• Fossil fuel deposits
• Soil organic matter
• Atmosphere
• Terrestrial plants

Question 5

What % of wood is carbon?

Answer 5

50%

Question 6

Why is soil an important component of the carbon cycle?

Answer 6

Because it can absorb and store carbon over moderate time periods.

Question 7

Define vegetation succession.

Answer 7

Over 100s of years, the plant species evolves and becomes more diverse, benefitting from a supply of carbon from the soil.

Question 8

Define sere.

Answer 8

A vegetation succession that relates to a specific environment.

Question 9

What is a climatic climax?

Answer 9

When a sere reaches dynamic equilibrium - usually in response to the climate.

Question 10

Photosynthesis is a transfer. Define photosynthesis.

Answer 10

The process whereby plants use light energy from the sun to produce carbohydrates in the form of glucose.

Question 11

In photosynthesis, what does light energy do?

Answer 11

The energy converts carbon dioxide from the air and water from the soil into glucose. During this, oxygen is released as a byproduct.

Question 12

In respiration, what is the glucose used for?

Answer 12

Respiration

Question 13

What happens if not all of the glucose is used in respiration on photosynthesis?

Answer 13

It is converted into starch, which is insoluble but can then be converted back into glucose for respiration.

Question 14

What happens in respiration?

Answer 14

Glucose is converted into energy that can be used for growth and repair, movement and control of the body temperature in mammals.
Carbon dioxide is also then returned to the atmosphere - mostly by exhaled air.

Question 15

What happens during decomposition?

Answer 15

Carbon from the bodies of the dead animals is returned to the atmosphere as carbon dioxide.

Some organic material passes into the soil where it may be stored for 100s of years.

Question 16

What happens in combustion?

Answer 16

When organic material is burned in the presence of oxygen, it is converted into energy, carbon dioxide and water.

The CO2 is released into the atmosphere, returning the carbon that may have been stored for millions of years otherwise.

Question 17

What happens during burial and compaction?

Answer 17

Over millions of years when organic sediments containing carbon are buried and compacted, they form hydrocarbons such as coal and oil.

Question 18

What do corals and shelled organisms do?

Answer 18

They take up carbon dioxide from water and convert it into calcium carbonate to build up their shells. When they die, their shells accumulate on the sea bed. Some of the carbonates dissolve, releasing CO2. The rest compact to form limestone and store carbon for millions of years.

Question 19

What is carbon sequestration?

Answer 19

An umbrella term used to describe the transfer of carbon form the atmosphere to plants, soils, rock formations and oceans.

Question 20

What is Carbon Capture Storage (CCS)?

Answer 20

A recent term used to describe the technological capturing of carbon emitted from power stations.

Question 21

What does weathering involve?

Answer 21

The breakdown or decay of rocks in their original place, at or close to the surface.

This is due to CO2 being absorbed by rainwater and forming mildly acidic carbonic acid. Through a series of chemical reactions, rocks slowly dissolve with the carbon being held in solution.

Question 22

What is the carbon cycle?

Answer 22

The complex processes that carbon undergoes as it is transformed from organic carbon to inorganic carbon.

Question 23

What is organic carbon?

Answer 23

The form of carbon found in living organisms eg plants and trees.

Question 24

Important examples of carbon compounds include…

Answer 24

• carbon dioxide found in atmosphere, soils, oceans
• methane found in atmosphere, soils, oceans, sedimentary rocks
• calcium carbonate found in calcareous rocks, oceans, skeletons and shells of ocean creatures
• hydrocarbons found in sedimentary rocks
• bio-molecules

Question 25

What are bio-molecules?

Answer 25

Complex carbon compounds produced in living things.

Proteins, carbohydrates, fats, oils and DNA are all examples of them.

Question 26

What is the primary source of carbon?

Answer 26

The Earth’s interior. It was stored in the mantle when the Earth formed. It escapes from the mantle at destructive and constructive plate boundaries as well as hot-spot volcanoes.

Much of the CO2 released at destructive margins is derived from the metamorphism of carbonate rocks subduction with the ocean crust.

Question 27

Carbon is removed into long term storage by…

Answer 27

Burial of sedimentary rock layers (especially coal and black shales and carbonate rocks like limestone).