The carbon cycle and energy security EQ1

Question 1

What does carbon moving between the carbon pathway refer to?

Answer 1

Carbon existing in gas, liquid and solid forms and biotic and abiotic forms.

Question 2

Why has the balance of atmospheric gases changed over geological time?

Answer 2

Because of Earth’s changing systems and processes.

Question 3

What happened to the atmosphere during the Precambrian period?

Answer 3

Volcanic activity added carbon dioxide, water and sulphur dioxide to the atmosphere at an exponential rate.

Question 4

What happened when primitive bacteria such as cyanobacteria started photosynthesising 3 billion years ago?

Answer 4

Oxygen was added to the atmosphere, while carbon dioxide was absorbed from it.

More complex organisms developed, due to higher oxygen levels.

Question 5

How is limestone formed by marine organisms?

Answer 5

Calcium carbonate.

Marine phytoplankton absorb carbon through photosynthesis.

Remains accumulate on the seabed.

Over time, this is compacted to form limestone rock.

Question 6

How else is limestone formed?

Answer 6

Direct precipitation of calcium carbonate from salt/freshwater.

Evaporation of sea water, which leaves behind calcium carbonate deposits.

Question 7

What happens to carbon during chemical weathering?

Answer 7

Rain falls through the air - becomes a carbonic acid.

Dissolves calcium carbonate.

Erosion processes transfer dissolved carbon, forming deposits on the seabed, eventually forming new rock.

Question 8

What is the first stage in the formation of coal?

Answer 8

The highest temperatures/pressures concentrate carbon to produce anthracite, which has a high energy potential. Source material must contain 2 per cent of organic carbon for this to happen.

Question 9

What percentage of source material must organic carbon contain for carbon to produce anthracite?

Answer 9

2%.

Question 10

What is the second stage in the formation of coal?

Answer 10

Anaerobic reactions convert over 90 per cent of organic carbon into crude oil.

Question 11

What happens to the crude oil in the formation of coal?

Answer 11

Crude oil moves into permeable and porous rock layers, due to low density.

Becomes trapped within anticlines of impermeable rock.

Question 12

What is an anticline?

Answer 12

Upfold of impermeable rock.

Question 13

What percentage of carbon, and what percentage of hydrogen does crude oil contain?

Answer 13

85% carbon.

13% hydrogen.

Question 14

How is methane created?

Answer 14

Created during coal and oil formation - trapped within the sedimentary rock layers.

Question 15

What does diagenesis refer to?

Answer 15

The long-term process where sediments are changed into sedimentary rocks.

Question 16

How do tectonic forces release carbon into the atmosphere?

Answer 16

Carbon-rich sedimentary rocks come into contact with extreme heat, which causes chemical changes and the release of carbon dioxide into the atmosphere.

Question 17

How many million tonnes of carbon dioxide does volcanic activity release?

Answer 17

300 million tonnes every year.

Question 18

Why is carbon dioxide the most common volcanic gas?

Answer 18

Least soluble - is degassed earlier in eruptions.

Question 19

What happens to carbon at subduction zones?

Answer 19

Carbon dioxide is released at shallow crustal depth.

Question 20

Why is Mount Etna in Italy the most actively degassing volcano in Europe?

Answer 20

Because of limestone and dolomite rocks from Tethys Ocean underneath.

Question 21

What does the biological carbon pump refer to?

Answer 21

Carbon entering the food web via other organisms that use carbon to make their shells and skeletons (calcium carbonate).

Question 22

Which type of water holds more gas; cold/deep water or warm/shallow water?

Answer 22

Cold/deep water. Slow-moving deep ocean currents hold carbon dioxide.

Question 23

Explain why the Southern Ocean may not be such an effective carbon sink in the future.

Answer 23

Deep water rises very gradually to the surface, where it absorbs carbon dioxide from the atmosphere.

Question 24

What is the role of large gyres?

Answer 24

Moving warm tropical water towards the poles, and colder water towards the equator.

Question 25

What happens to the water in thermohaline circulation?

Answer 25

Cold dense salty water sinks, while warmer water upwells, replacing it.

Question 26

What is the world-scale thermohaline circulation driven by?

Answer 26

Differences in density.

Question 27

Why does it take hundreds/thousands of years for deep ocean water to return to the surface?

Answer 27

The flow rate is slow (1-3 km per day), due to high density.

The volume of water moving in the deep ocean is 400,000 km3.

Question 28

How is methane produced?

Answer 28

Anaerobic decomposition of organic matter by termite digestive processes.

Question 29

What is the process called when the Earth moves around the Sun over long timescales?

Answer 29

The Milankovitch cycle.

Question 30

Why is the sun’s energy able to pass through denser gases of the lower atmosphere?

Answer 30

Short wavelength.

Question 31

Why is it difficult for the heat energy that is reflected back towards space from the Earth’s surface, to travel through denser gases, such as carbon dioxide and methane?

Answer 31

Longer wavelength - atmosphere absorbs heat.

Question 32

What is the name of the geological period we are living in today?

Answer 32

Holocene.

Question 33

What have scientists in Antartica and Greenland found there to be a positive correlation between?

Answer 33

Carbon dioxide, methane and temperature, which corresponds to ice ages and the past inter-glacial periods.

Question 34

What is the name of the cells that carbohydrates are created in?

Answer 34

Autotrophs.

Question 35

How does photosynthesis balance respiration?

Answer 35

Combines oxygen with the carbohydrate and releases carbon dioxide and water.

Question 36

Give two ways how oxygen and carbon dioxide can be released.

Answer 36

By the weathering of sedimentary rocks and water vapour.