Unit 4: The Global Carbon Cycle

Question 1

Define the carbon cycle

Answer 1

The carbon cycle is a biochemical cycle by which carbon moves from one part of the planet to another

Question 2

What % of the planets biomass is made of carbon?

Answer 2

50%

Question 3

How many metric tonnes of carbon is stored in the biosphere?

Answer 3

560 billion

Question 4

What % of all the planets carbon is stored in the biosphere?

Answer 4

0.0012%

Question 5

How many metric tonnes of carbon is stored in the atmosphere?

Answer 5

750 billion

Question 6

What % of all the planets carbon is stored in the atmosphere?

Answer 6

0.0017%

Question 7

What % of all the planets carbon is stored in the pedosphere?

Answer 7

0.0031%

Question 8

What % of all the planets carbon is stored as fossil fuels?

Answer 8

0.004%

Question 9

What % of all the planets carbon is stored in the hydrosphere?

Answer 9

0.0038%

Question 10

How many metric tonnes of carbon is stored in the hydrosphere?

Answer 10

38,000 billion

Question 11

As part of the lithosphere where is over 99.9% of the worlds carbon stored?

Answer 11

Marine sediment and sedimentary rocks such as limestone.

Question 12

What time period does the slow carbon cycle operate over?

Answer 12

Between 100 and 200 million years

Question 13

A type of chemical weathering known as carbonation weathering requires carbonic acid. How and where does carbonic acids form?

Answer 13

Atmosphere contains CO2 which combines with water vapour to make carbonic acid

Question 14

The carbon in the ocean is used by what organisms and for what purpose?

Answer 14

Shells and skeletons of marine creatures as calcium carbonate.

Question 15

What happens to carbon in these organisms?

Answer 15

They die, fall to bottom of sea, over millions of years they will compact down to create sedimentary rocks like limestone under heat and pressure, carbon from organic matter trapped in the sediment is converted into fossil fuels.

Question 16

What is the name of the process in which atmospheric carbon is stored in a liquid or solid form in the lithosphere?

Answer 16

Sequestration

Question 17

What happens to the carbon stored on the ocean floor at convergent plate boundaries when subduction occurs?

Answer 17

Under extreme heat and pressure the carbon contained in the rocks is released and rushes back to the surface. Every year volcanoes around the world release about 200 million tonnes of carbon dioxide back into the atmosphere.

Question 18

Why is rainfall naturally acidic?

Answer 18

Due to CO2 in the air. Industry can make it more acidic.

Question 19

What happens to rocks containing calcium carbonate, such as limestone, when it comes into contact with acidic solutions?

Answer 19

It bubbles and the rocks/limestone gets cared away.

Question 20

Summarise the process of chemical weathering in the carbon cycle

Answer 20

1. Atmospheric carbon dioxide is dissolved in water vapour and forms carbonic acid, Precipitation is naturally acidic (carbonic acid)
2. Carbonic acid reacts with rocks containing calcium carbonate e.g. limestone through carbonation weathering and creates calcium bicarbonate
3. Calcium bicarbonate is soluble in water and is carried away in solution by runoff and percolating water
4. Soluble calcium bicarbonate is transferred to the ocean by river runoff

Question 21

Whats a Karst landscape?

Answer 21

Areas where limestone dominates the surface rock type will over millions of years’ experience extensive carbonation weathering, which overtime can lead to distinctive landscapes known as karst landscapes - a limestone pavement is an example. Location example = Malham Cove, Yorkshire, England

Question 22

What happens to the calcium bicarbonate?

Answer 22

1. rivers, throughflow and groundwater transport calcium bicarbonate to the oceans
2. at the bottom of the oceans large amounts of dissolved inorganic carbon accumulate (carbon sequestration) to form carbonate sediments Some of this sediment will be from the bicarbonate created by carbonation weathering.
3. In the oceans carbonate is used by marine organism such as plankton and shellfish to make their shells.

Question 23

What happens to the carbon stored on the ocean floor?

Answer 23

In subduction zones at convergent plate boundaries some of the carbon sediments are converted into magma which may result in volcanic eruptions, emitting CO2 back into the atmosphere. Each year about 200 million tons of CO2 are released into the atmosphere by volcanoes.

Question 24

What are other effects of Plate tectonics on the carbon cycle?

Answer 24

Fold mountains which form at convergent boundaries will force carbonate-rich sediments and rocks, such as limestone, upwards. An example of this is the Himalayas. Once exposed to precipitation carbonation weathering will occur - back to the starting point.

Question 25

What is the fast carbon cycle?

Answer 25

The fast carbon cycle is largely the movement of carbon through life forms on earth: the biosphere. The time it takes carbon to move through the fast carbon cycle is measured in the life span of a plant or animal. Between 1000-100,000 mullion metric tonnes of carbon move through the fast carbon cycle every year through all life forms.

Question 26

Describe the amount of carbon in the oceans?

Answer 26

The oceans contain 50 times the amount of carbon stored in the atmosphere. 7% of the carbon in the ocean is dissolved CO2 the remaining 93% is within the organisms that live there.

Question 27

Once diffused in the ocean the carbon can follow different pathways known as what?

Answer 27

The Physical (inorganic) pump
The Biological (organic) pump

Question 28

Describe the physical (inorganic) pump

Answer 28

Movement of dissolved CO2 around the ocean

CO2 can be moved around the ocean by thermohaline ocean currents, which form due to variations in ocean temperatures and salinity.
Carbon can be transferred from the surface to the deep ocean in areas where old dense surface waters sink known as ‘downwelling’ - usually in polar regions.
Carbon can be transferred from the deep ocean to the surface in areas where deep waters rise known as ‘upwelling’ - usually in Equatorial regions.

Question 29

Describe the biological (organic) pump

Answer 29

A major source of carbon sequestrain, driven by ocean phytoplankton absorbing CO2 via photosythesis

1. diffusion of CO2 in to ocean surface
2. phytoplankton photosynthesise and use diffused CO2 storing it in new biomass
3. as part of the ocean food chain phytoplankton are eaten by zooplankton which in turn are eaten by other marine organisms, passing the carbon in carbohydrates
4. when organisms respire they release CO2 some of which will pass back to the atmosphere
5. marine organisms die and sink to seafloor adding to carbon-rich sediments on the floor
6. over millions of years organic carbon-rich sediment can form fossil fuels

Question 30

What is photosynthesis?

Answer 30

A biochemical process operating in plants that convert CO2 and water into carbohydrates (glucose) and oxygen.

Question 31

What is respiration?

Answer 31

Its a chemical reaction that happens in all living cells, including plant cells and animal cells in which energy is released from glucose so that all the other processes needed for life can happen. CO2 is released back into the atmosphere as a by-product of respiration. Just like photosynthesis rates of respiration will vary across the planet.

Question 32

What is decomposition?

Answer 32

Plants and animals die and decompose. Decomposition is carried out by organisms known as decomposers such as fungi and bacteria which secrete enzymes that aid the breakdown of organic compounds. Other organisms known as detritivores such as earthworms aid decomposition as they feed on dead organic matter. The process of decomposition releases CO2 and CH4 back into the atmosphere.

Question 33

How do earthworms affect infiltration rates of soil?

Answer 33

They enhance soil structure which can improve the infiltration rates of water into the soil. The worms burrow through the soil which creates channels allowing water allowing to penetrate deep into the soil. The presence of earthworms increase the overall porosity of the soil.

Question 34

Whats combustion?

Answer 34

The process of combustion releases CO2 into the atmosphere. The two main stores of carbon that combust are living matter through wildfires, and fossil fuels (coal, oil and gas)

Question 35

What are some key facts about wildfires?

Answer 35

every year wildfires burn 3-4 million km^2of the earths land area
wildfires account for up to 20% of total global greenhouse gas emissions
climate change is increasing the risk of wildfires - a 1.5 C rise could lead to a 40% increase in wildfires

Question 36

What are 3 key components required to initiate a wildfire?

Answer 36

1. Fuel - vegetation, shrubs, leaf litter
2. Source of ignition - lightning
3. Climate and recent weather - arm, wet and windy enough

Question 37

What are natural causes of wildfires?

Answer 37

Lightning and hot volcanic material

Question 38

What are human causes of wildfires?

Answer 38

Clearing land for agriculture
Accidental - dropped cigarette, camp fire, fireworks
Malicious - arson

Question 39

Why are rainforests naturally fire resistant?

Answer 39

They are too wet so they lack the climate component

Question 40

How is human activity extending the range of areas affected by wildfires?

Answer 40

Deforestation and draining reduces places with natural fire resistance - creating a more flammable environment.

Question 41

What were the causes of the Australian wildfires in 2019?

Answer 41

Temperature, humidity, wind and dryness. Climate change. In some places there’d been no rain for years.

Question 42

What were the impacts of the Australian wildfires in 2019?

Answer 42

Thousands evacuated from their homes
Hundreds of schools closed
At least 3 people killed
Loss of property

Question 43

What were the causes of the Lincolnshire UK wildfire in 2022?

Answer 43

Hottest ever temp in the UK was recorded in Lincolnshire on 19th July - 40.3 C in Coningsby

Question 44

What were the impacts of the Lincolnshire UK wildfire in 2022?

Answer 44

Fire nearly reached a grain store, a propane tank and 4 houses
Half the country’s 48 fire engines now have access to the adapters to farmers tank to hold much more water.

Question 45

Describe the burning of fossil fuels

Answer 45

Fossil fuels are oil, gas and coal which form over millions of years from the burial of organic carbon-rich sediments. Oil and gas on the ocean floor. Coal from peat. 85% of global energy is derived from fossil fuels and is the main source of anthropogenic atmospheric CO2 - an important greenhouse gas. Burning of fossil fuels releases CO2 which is the major cause of climate change. Global average temperatures have increased by 1C since 1880.