6.B/C

Question 1

Limestone rocks

Answer 1

Contain high concentration of calcium carbonate formed partly by the shell building organisms such as coral.

They extracted minerals from the seawater and from marine phytoplankton which absorb carbon via photosynthesis which would accumulate on ocean floor over long periods of time:

-Cemented and lithified together.

Question 2

Biologically derived carbon

Answer 2

• Biologically derived carbon in rocks such as shale when carbon from organisms is embedded in layers of mud.
• Over millions of years heat and pressure compress the mud and carbon, forming shale.

Question 3

Carbon fossil fuels

Answer 3

• Made up to 300 million years ago from the remains of dead organic material.
• Organisms once dead sink to the bottom of rivers and sewer and are covered in mud and silt which cause them to decay anaerobically which happens over a millennia.
• When the organic matter builds up faster than it can decay, layers of organic carbon become fossil files instead on shale.

Question 4

Geological carbon release

Answer 4

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Question 5

Weathering

Answer 5

• Rain water in carbonic acid takes in CO2 from the air and then dissolves it in rock materials to form new minerals such as calcium carbonate.
• Rivers carry these minerals to the sea where they are deposited and buried eventually forming new rock.

Question 6

Tectonic forces

Answer 6

-Tectonic forces may bring carbon-rich sedimentary rocks into contact with extreme heat which causes chemical changes and the release of CO2 back into the atmosphere.

Question 7

Volcanic activity

Answer 7

• Volcanic activity at subduction zones, constructive plate boundaries or intra-plate locations cause gases (including CO2) to be released into the atmosphere.
• The out-gassing is also common in geothermal area as, such as the CO2-rich hot springs in Yellowstone, Iceland and New Zealand.

Question 8

Volcanic activity facts

Answer 8

• Releases 300 million tonnes of CO2 every year.
• CO2 is the second most abundant volcanic gas as CO2 is the least soluble and so degassed earlier in the eruption.
• Carbon is recycled at subduction zones with carbonate rocks dragged into the mantle, creating an upper mantle carbon concentration of between 50 and 250 ppm.