Geochemical Carbon and Oxygen Cycles

Question 1

How much do carbon and oxygen make up in the atmosphere (in percentages)?

Answer 1

Carbon = 0.04205

Oxygen = 21%

Question 2

What are the differences between organic and inorganic carbon?

Answer 2

Inorganic:

Carbon extracted from ores and minerals

Organic:

Found in nature from plants and living things e.g. phytoplankton

Question 3

What are the two ways carbon leaves the atmosphere?

Answer 3

1) Dissolved in rainwater to form carbonic acid

2) Direct removal of carbon from the atmosphere by silicate rocks

Question 4

What does weathering form when reacting with silicate rocks?

Answer 4

Silicate reacts with carbon dioxide to produce limestone (calcium carbonate)

Question 5

How is carbon put in long-term storage in the lithosphere?

Answer 5

Runoff from rocks moves carbonate ions into the ocean

Limestone and HCO3- buried by tectonic movements

Question 6

Where can limestone move after being buried?

Answer 6

Subducted into the mantle by tectonic forces

Forms silicate metamorphic rocks which releases CO2 into the mantle

CO2 from the mantle can then be released through volcanic degassing which completes the cycle

Can take a single carbon atom billions of years to complete this cycle

Question 7

What controls atmospheric CO2?

Answer 7

Ocean carbon cycling (MINOR)

Inorganic carbon cycle (MAJOR) - CO2 and silicate rocks to from limestone

Inorganic carbon cycle (MAJOR) - limestone carbonate forms CO2 and silicate rock

Biosphere carbon cycling (MINOR) - photosynthesis and respiration

Question 8

What are the geological impacts of oxygen?

Answer 8

Iron pyrite is very reactive and reacts with oxygen to from iron oxides

This process also produces sulphates which in the presence of water produces sulphuric acid

Sulphuric acid can then react with other carbon containing rocks to produce CO2 and/or carbonate ions

Question 9

What is the major long-term control of atmospheric oxygen?

Answer 9

Produced by the formation of pyrite

Removed by the weathering of pyrite

Question 10

What are some common misconceptions about trees and the uptake of CO2?

Answer 10

Planting trees removed CO2 by use in photosynthesis

Planting trees removes CO2 by storage in plant tissue

Oxygen levels are determined by trees and rainforests

Question 11

How were fossil fuels created?

Answer 11

Large plants fell into swamps during the carboniferous

Buried into the swamp before decomposition (fungi had not evolved yet)

Low oxygen environment and no decommission allowed the formation of fossil fuels