Carbon

Question 1

How has the extraction and burning of hydrocarbons changed the carbon cycle?

Answer 1

Since the industrial revolution, particularly in the western world, we have burnt increasing quantities of fossil fuels to power industries, transport and domestic purposes.

When plants lived millions of years ago, they sequestered carbon from the Earth’s atmosphere. These plant remains were buried deep under other sediments which became sedimentary rocks. As the remains were compacted they formed oil and natural gas.

Question 2

How have land use changes caused change in the carbon cycle?

Answer 2

1. Change from intensive to extensive farming practices, associated with this is increased demand from a growing global population and increased demand for meat from new middle classes in developing countries.
2. Deforestation and planting of palm oil palms and soya plantations. Also conversion of forest to grassland for grazing
3. Draining of wetlands which are a massive carbon if they are maintained, because organic matter falls into the water and decomposition is very slow - so the carbon is locked away. When drained, this can’t happen.

Urbanisation means that areas which were once soil and vegetation are concreted / tarmaced over. More urban areas also means more industry and transport (so more fossil fuel use).

Question 3

How has deforestation cause change in the carbon cycle?

Answer 3

1. When trees are burnt, CO2 is released into the atmosphere. The soil is more prone to erosion, becomes less fertile and hold less CO2.
2. Trees are felled or burnt so that the timber can be used for other purposes (commercial farming, hydroelectric power, cattle ranching and mining).

Question 4

What is a carbon sink?

Answer 4

A store that absorbs more carbon than it releases.

Question 5

What’s a carbon source?

Answer 5

A store that releases more carbon than it absorbs.

Question 6

What are carbon fluxes?

Answer 6

The change in the amount of carbon held in each store over time (from minutes to millions of years)

Question 7

How is carbon stored in permafrost? By what processes?

Answer 7

• organic matter Rabat frozen in the soil in tundra regions cannot decompose, which prevents the release of carbon dioxide and methane into the atmosphere / water / soil
• increased melting of the permafrost. Due to climate change it is leading to a transfer of CO2 and methane into the atmosphere as the ice melts.

Question 8

How is carbon stored in the atmosphere?

Answer 8

• held in the atmosphere as carbon dioxide
• in recent decades, the amount carbon dioxide has increased due to emissions from power stations, vehicles and deforestation. This has led to the enhanced greenhouse effect and climate change.

Question 9

How is carbon stored in living vegetation? By what processes?

Answer 9

• plants convert energy from the sun unto carbohydrates that support life.
• plants can store carbon for many years and transfer it to the soil, oceans, seabed, or atmosphere when they die.
• deforestation releases this carbon back into the environment.

Question 10

How is carbon stored in rocks?

Answer 10

• this is the largest store. It’s a long term store, with rocks gaming millions of years to form.
• rocks eg chalk and limestone are mainly composed of carbon (fossilised remains of marine animals)
• fossilised organic matter is also trapped within the lithosphere, stored in coal, oil and natural gas.

Question 11

How is carbon stored in soil?

Answer 11

• soil contains rotting organic matter and weathered rock, and are important long term stored of carbon - it can be stored for 100s of years.
• deforestation, land use change and soil regions can however release this stored carbon very quickly.

Question 12

How is carbon stored in the ocean?

Answer 12

• dissolved carbon is stored in surface ocean waters.
• living organisms including plankton and shelled organisms extract carbon from the water and use it to form their shells and bodies.
• when organisms die, they sink to the ocean floor where carbon is stored as ocean sediments. They also decay releasing CO2 to deep ocean waters. This sinking of carbon is called the carbon pump and is a slow process.

Question 13

How do cold conditions affect stores and transfers of carbon?

Answer 13

• when cold, soils freeze over vast areas of land, stopping transfers of carbon
• decomposers would have been less effective, so carbon transfers to the soil would have been reduced
• less water would have flowed into the oceans as it is locked in ice and snow on land. There would be less sediment transfer along rivers and less build up of sediment on the ocean floor
• chemical weathering processes would have been more active as cold water can hold more carbon dioxide
• forest coverage would be very different both in: total area and geographical location. This would have affected the significance and distribution of processes such as photosynthesis and respiration

Question 14

How do warm conditions affect the stores and transfers in the carbon cycle?

Answer 14

Carbon stored within permafrost (containing gases such as methane) is now being released into the atmosphere which further enhances the greenhouse effect, leading to increased warming. This is an example of a positive feedback loop leading to a further destabilisation of the system.

Question 15

How can wildfires have regional impacts?

Answer 15

They turn forests from carbon sinks to carbon sources, because combustion returns huge quantities of carbon back into the atmosphere.

Question 16

What are fossil fuels composed of?

Answer 16

Hydrocarbons

Question 17

How much is land use responsible for global carbon emissions?

Answer 17

10%

Question 18

Give examples of farming processes that release carbon.

Answer 18

• ploughing
• harvesting
• rearing livestock
• using machines powered by fossil fuels
• artificial fertilisers

Question 19

How do cattle release methane?

Answer 19

They ruminate (regurgitate food and mask ate it a second time - chewing the cud) which produces methane as a by-product.

Question 20

How many tonnes of methane do cows release into the atmosphere in the USA?

Answer 20

5.5 million

Question 21

How much are cattle in the USA responsible for carbon emissions?

Answer 21

20%

Question 22

Explain how trees could be carbon neutral.

Answer 22

In a natural system, when a tree dies, it naturally decomposes very slowly and releases carbon over a long period of time. During that time, new vegetation begins to grow the quickly compensates for the carbon being released by the dead tree 🌳

Question 23

Urban areas occupy about __% of the total land area.

Answer 23

2

Question 24

What are the major sources of carbon emissions in urban areas?

Answer 24

• transport
• development of industry
• conversion of land from natural to urban
• cement production for building sector

Question 25

How do farming practices cause change in the carbon cycle?

Answer 25

1. Most artificial fertilisers are made from fossil fuels. Spreading here on the land puts carbon into rivers as surface runoff and then into the atmosphere. 2. Digestion by livestock (particularly ruminants) releases methane. More meat and dairy we eat = more methane. 3. Methane also released as a byproduct of some arable farming (it's produced by bacteria during decomposition). 4. Rice grows in water - the perfect environment for methane releasing bacteria during anaerobic respiration.

Question 26

What is the carbon budget?

Answer 26

It uses data to describe the amount of carbon that is stored and transferred within the carbon cycle.

Question 27

What is carbon commonly measured in?

Answer 27

Petagrams (pg)

Question 28

Why is a relatively low amount of carbon stored in the atmosphere and plants?

Answer 28

Because the carbon transfers are extremely active, with carbon constantly flowing back and forth between the atmosphere and the land.

Question 29

Anthropogenic activities include...

Answer 29

Burning of fossil fuels, combustion.

Question 30

How does vegetation impact upon global climates?

Answer 30

Because vegetation removes carbon dioxide and releases water and oxygen.

Question 31

Why may regions with dense vegetation experience increased levels of humidity and cloud cover?

Answer 31

Because in these areas, there is more photosynthesis and respiration.

Question 32

What does carbon stored in grass provide?

Answer 32

Fodder for animals

Question 33

What does carbon in the form of organic matter provide?

Answer 33

It is essential for plant growth and the production of food.

Question 34

How can volcanic eruptions have a small scale impact on climate?

Answer 34

Because when they erupt, they release carbon dioxide into the atmosphere along with ash and other gases. This absorbs mire incoming radiation from the sun and can lead to a volcanic winter - a reduction in global temperatures.

Question 35

How may increased oceans temperatures cause more clouds to form?

Answer 35

Because these warmer temperatures along with more sunshine attract marine phytoplankton (which release DMS), which promote condensation - and therefore cloud formation over the ocean in a negative feedback loop.

Question 36

How do higher temperatures create a positive feedback loop? (Vegetation).

Answer 36

Higher temperatures = increased growing season for plants = increased absorption of CO2 from the atmosphere

Question 37

How do higher temperatures lead to a positive feedback loop? (Permafrost).

Answer 37

Higher temperatures = melting permafrost (particularly in Siberia) = organic matter trapped in this permafrost (acts as an important store) = on melting, the organic matter in the permafrost starts to decompose as oxygen is introduced = the bacteria involved in decomposition produce carbon dioxide and methane as a waste product = the gases bubble to the surface and escape into the atmosphere

Question 38

Impacts of warm conditions on carbon stores and transfers?

Answer 38

- carbon is stored within the permafrost (along with other gases eg methane) and is now released into the atmosphere where it further increases the greenhouse effect, leading to increased warming.

Question 39

Impacts of cold conditions on carbon stored and transfers?

Answer 39

- chemical weathering processes more active because cold water can hold more carbon dioxide - forest coverage would have been different in terms of geographical location and total area. This affects the significance and distribution of processes such as photosynthesis and respiration - decomposers less effective, so carbon transfer to soils reduced - soil frozen over vast areas of land, stops transfers of carbon - less water flows into the ocean as if is locked up as snow and ice on land. This means less sediment transfer along rivers and less sediment buildup along ocean floor

Question 40

How can volcanic activity lead to sedimentary rocks?

Answer 40

Volcanic eruptions create igneous silicate ricks which are weathered which converts atmospheric CO2 to carbonate minerals in solution. These become ocean sediments and may become sedimentary rocks.