3.1.1.3 carbon cycle W&C

Question 1

what is the major source of carbon

Answer 1

the earths interior, it was stored in the mantle when the earth was formed

Question 2

where does carbon escape from the mantle

Answer 2

plate boundaries as well as hot spots

Question 3

where is carbon distributed in the world

Answer 3

CO2 in the atmosphere
dissolved in the oceans
held in biomass in living or dead organisms
in carbonate rocks

Question 4

how is carbon put into long term storage

Answer 4

by burial and compaction of sedimentary rock layers including coal, shale and limestone

Question 5

how is the amount of carbon measured

Answer 5

in gigatonnes

1 gigatonne is the equivalent to 1 billion tonnes

Question 6

what is carbon found in

Answer 6

all life forms as well as sedimentary rocks, diamonds, graphite, coal, oil and natural gas

Question 7

why is the recycling of carbon essential for life on earth

Answer 7

enables food to be provided for plants and animals and energy sources to be created for industrial development

Question 8

what are some important carbon compounds

Answer 8

CO2
CH4 (methane)
CaCO3 (calcium carbonate)
hydrocarbons

Question 9

what subsystems is carbon found in

Answer 9

lithosphere, atmosphere, hydrosphere, biosphere and cryosphere

Question 10

how much carbon is stored in the lithosphere

Answer 10

over 99.9%

Question 11

how much carbon is in the atmosphere

Answer 11

0.001%

Question 12

how much carbon is in the hydrosphere

Answer 12

0.04%

Question 13

how much carbon is in the biosphere

Answer 13

0.004%

Question 14

how much carbon is in the cryosphere

Answer 14

less than 0.01%

Question 15

what are transfers/fluxes

Answer 15

carbon moving from one store to another in a continuous cycle

Question 16

what is a net carbon sink

Answer 16

more carbon enters than leaves

Question 17

what is a net carbon source

Answer 17

more carbon leaves than enters

Question 18

what are the 7 major carbon flows

Answer 18

photosynthesis, respiration, decomposition, combustion, weathering, ocean uptake and loss (diffusion) and sequestration

Question 19

what is photosynthesis + extra detail for 4 marker

Answer 19

the transfer of carbon stored in the atmosphere to biomass

plants and phytoplankton use energy from the sun to change CO2 and water to glucose and oxygen which allows them to grow

CO2+H2O+sunlight > CH2O+O2

Carbon is then passed through the food chain and released through respiration and decomposition.

Question 20

what is respiration + extra detail

Answer 20

the transfer of carbon from living organisms to the atmosphere

Plants and animals break down glucose for energy, releasing CO2 and methane (which contains carbon) in the process

Respiration is the opposite of photosynthesis, these processes are not in balance however. Not all organic matter is oxidized. Some is buried in sedimentary rocks

Question 21

what is decomposition + extra detail

Answer 21

transfer carbon from dead biomass to the atmosphere and the soil

After death, bacteria and fungi break organisms down. CO2 and methane are released

Some carbon is transferred to the soil in the form of humus

Decomposition ensures that carbon can be continually recycled into the soil and made available for life

Question 22

what is combustion + extra detail

Answer 22

the transfer of carbon stored in living, dead or decomposed biomass to the atmosphere by burning

occurs when any organic material is burned in the presence of oxygen to five of CO2, water and energy

the organic material includes any vegetation or fossil fuel such as natural gas, oil or coal

Question 23

what is weathering + extra detail

Answer 23

chemical weathering transfers carbon from the atmosphere to the hydrosphere and biosphere

atmospheric carbon reacts with water vapour to form mildly carbonic acid, this acid rain falls onto rocks and a chemical reaction occurs to dissolve the rocks, this may be washed away to sea where it reacts with CO2 dissolved in the water to form calcium carbonate which is used by sea creatures to make their shells

Question 24

what is ocean uptake and loss (diffusion) + extra detail

Answer 24

CO2 is directly dissolved from the atmosphere to the ocean, it may be taken up by organisms that live in the water such as plankton

carbon is also transferred to the oceans when carbon rich water from deep in the oceans rises to the surface and releases CO2

Question 25

what is sequestration + extra detail

Answer 25

carbon from the atmosphere can be sequestered (captured and held) in sedimentary rocks or as fossil fuels, this effectively puts carbon into long term storage

Rocks and fossil fuels form over millions of years when dead animals and plant material in the ocean falls to the floor and is compacted

Question 26

how does carbon change in stores over time

Answer 26

some carbon flows are relatively fast (photosynthesis and respiration) whereas some are much slower (it takes millions of years for carbon to be sequestered into sedimentary rocks)

Question 27

how does carbon change in stores over scale

Answer 27

occur at plant scale, seral scale, ecosystem scale and continental scale

Question 28

what is primary succession

Answer 28

when bare rock is colonised by plant and animal communities over time, at the climax community the cycling of carbon is greater than at the beginning

Question 29

what are the two changes to the carbon cycle over time due to natural variation

Answer 29

Wildfires and volcanic activity

Question 30

how do wildfires cause change to the carbon cycle over time

Answer 30

They rapidly transfer large quantities of carbon from biomass (or soil) to the atmosphere as a result of combustion

As wildfires result in a loss of vegetation in the short term, photosynthesis decreases so less carbon is removed from the atmosphere.

In the longer term, however, fires can encourage the growth of new plants. Secondary succession can occur as plants recolonise the area. As succession takes place more carbon will be taken from the atmosphere as a result of photosynthesis

Question 31

how does volcanic activity cause change in the carbon cycle over time

Answer 31

Carbon stored within the Earth in magma is released during volcanic eruptions. The majority enters the atmosphere as CO. This returns carbon that has been trapped for millions of years in rock deep

Recent volcanic eruptions have released much less CO2, than human activities (e.g. fossil fuel burning). At present, volcanoes emit between 130 and 380 million tonnes of CO2 per year

Question 32

what are the 4 changes in the carbon cycle of time due to human activity

Answer 32

Hydrocarbon fuel extraction and burning, deforestation, urbanisation and land use change

Question 33

what are hydrocarbons

Answer 33

fossil fuels are composed of carbon and hydrogen so are known as hydrocarbons

Question 34

how does hydrocarbon fuel extraction and burning cause change in the carbon cycle over time

Answer 34

Extracting and burning (combustion) of fossil fuels releases CO2 into the atmosphere.

Without human intervention, the carbon would remain sequestered in the lithosphere for
thousands or millions of years to come

Today, most of the world’s gas and oil is extracted from rocks that are 70-100 million years old.
The carbon has remained locked up in these deposits for all that time but, when burnt to generate energy and power, the stored carbon is released as CO2 into the atmosphere, accelerating the cycling of this carbon

Since the industrial revolution fossil fuels have been burnt in increasing quantities

According to the Intergovernmental Panel on Climate Change (IPCC), about 90% of the anthropogenic (human related) carbon release comes from the combustion of fossil fuels, primarily coal, but also oil and gas

Question 35

how do farming practices cause change in the carbon cycle over time

Answer 35

Agricultural activities release carbon dioxide into the atmosphere:

livestock release C02 and methane when they respire and digest food, this is the largest source of C02 within agriculture

Ploughing releases carbon stored in the soil, air is mixed in when soil is turned which increases soil microbial activity, results in soil ,alter being broken down more rapidly

Growing rice in rice paddies releases a lot of methane. This helps accounts for over 40% of agriculture-related greenhouse gas outputs occur in Asia

As the world’s population has risen, so has food production. As a result, carbon emissions from farming practices have increased. Mechanisation of farming has also increased CO2 emissions as more tractors and other farm vehicles are used across the globe

Question 36

how has deforestation cause change in the carbon cycle over time

Answer 36

Forests may be cleared for agriculture, logging, or to make way for development and urban sprawl

The UN Food and Agriculture Organisation (FAO) estimates that about 13 million hectares (an
area the size of Greece) of the world’s forests are cut down and converted to other land uses
every year.

if the cleared forest is burned, there is a
rapid flow of carbon from the biosphere to the atmosphere

Question 37

how does land use change cause change in the carbon cycle over time

Answer 37

the change of land use from natural or agricultural to urban is a major source of carbon. Replacing open countryside with concrete and tarmac is known as urbanisation

Vegetation is removed, or covered up, to make way for buildings – this reduces carbon storage in the biosphere

Globally, urban areas occupy 2% of the total land area. However, these account for 97% of all
anthropomorphic CO2 emissions

Question 38

what is the carbon budget

Answer 38

the difference between inputs and outputs of carbon into/out of a subsystem

Question 39

what is examples of the carbon budget

Answer 39

For example, in the atmosphere, inputs of carbon come from volcanic eruptions, burning fossil
fuels, respiration and ocean loss, and outputs occur through photosynthesis, sequestration,
decomposition, chemical weathering and ocean uptake

Question 40

what does the balance of inputs and outputs determine

Answer 40

whether it acts as a carbon source or sink

Question 41

where do natural systems ‘bank’ carbon

Answer 41

in biomass and by dissolution in the ocean system

Question 42

why is carbon important to ‘the land’

Answer 42

• allows plants to grow (photosynthesis, respiration and decomposition)
• because plants are primary producers in ecosystems, all consumers including livestock and humans depend on plants

Question 43

what effect would the carbon cycle have on ‘the land’

Answer 43

• more CO2 is available to plants and longer growing season due to warmer temps, more photosynthesis and plant growth, growth limits will depend on water and nutrient availability
• An increase in global temperatures could increase the frequency of wildfires, further increasing atmospheric CO2

Question 44

why is carbon important for the ocean

Answer 44

• organisms such as phytoplankton and seaweed use the CO2 during photosynthesis and other marine organisms to form calcium carbonate shells and skeletons

Question 45

what is the effect of carbon on the oceans

Answer 45

• More CO2 in the atmosphere means more acidic oceans as the oceans initially absorb more CO2 (ocean uptake). There has been a 30% change in ocean acidity since 1750. This is adversely affecting marine life, including coral reefs. Reef loss is linked to a fall in marine diversity
• Warmer oceans are certainly causing sea ice to melt. Arctic sea ice has retreated by 40% in the last 35 years. The loss of sea ice is resulting in a loss of a habitat for species of algae that support marine consumers as well as a loss of hunting grounds for larger predators like polar bears

Question 46

why is carbon important for the atmosphere

Answer 46

• The carbon cycle affects the amount of gases containing carbon (e.g. CO2 and methane) in the atmosphere. These are greenhouse gases and ensure that the climate is warm enough to support life on Earth

Question 47

what effect will carbon have on the atmosphere

Answer 47

• the concentration of greenhouses gases in the atmosphere increases temperatures are expected to rise causing rapid global warming. Greenhouse gas emissions have increased significantly in recent decades due to human activities such as deforestation and fossil fuel combustion. This has led to an enhanced greenhouse effect

Question 48

why is carbon important for the global climate (vegetation

Answer 48

• Vegetation plays a pivotal role in the carbon cycle and on global climates. Plants remove carbon dioxide and release water and oxygen. Regions with dense vegetation (e.g. tropical rainforests) experience high rates of photosynthesis and respiration. This increases levels of humidity, the amount of cloud cover and affects rainfall.
• Regions experiencing large-scale deforestation may become drier and less humid