AQA · A-Level · Geography

    Course version: 7037 · Version from Sept 2018

    Global distribution, and size of major stores of carbon – lithosphere,…

    Full specification wording

    The carbon cycle: Global distribution, and size of major stores of carbon – lithosphere, hydrosphere, cryosphere biosphere, atmosphere.

    The global carbon cycle comprises five major stores of varying sizes and distributions.

    Checked against the AQA 7037 specification (opens in a new tab) on .

    • Point 1 of 4
    • 4 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    The global carbon cycle comprises five major stores of varying sizes and distributions. The lithosphere is the largest store, containing over 99.9% of global carbon (approximately 100,000,000 PgC), primarily in sedimentary rocks like limestone and fossil fuels. The hydrosphere is the second largest (approximately 38,000 PgC), with most carbon dissolved in the deep ocean. The biosphere (approximately 3,190 PgC) stores carbon in living vegetation, soils, and peat, distributed heavily in tropical rainforests and boreal forests. The cryosphere stores carbon in permafrost (approximately 1,400 PgC), mainly in tundra regions. The atmosphere is the smallest major store (approximately 750 PgC) but is highly active, distributing carbon globally.

    What earns the marks

    • Identify the lithosphere as the largest carbon store, containing sedimentary rocks and fossil fuels.
    • Describe the hydrosphere's role, noting that the deep ocean stores significantly more carbon than the surface ocean.
    • Explain the distribution of the biosphere, highlighting the concentration of terrestrial carbon in tropical and boreal biomes.
    • Recognise the cryosphere as a significant store of frozen organic carbon in permafrost regions.
    • Compare the relative sizes of the stores, noting the atmosphere is comparatively small but crucial for regulating global temperatures.

    Common mistakes and how to put them right

    • Confusing the sizes of the biosphere and atmosphere.

      Put it right: The biosphere is significantly larger than the atmosphere.

    • Ignoring the cryosphere as a distinct carbon store.

      Put it right: Ensure permafrost is recognised as a major, vulnerable carbon reservoir.

    • Assuming the surface ocean holds the most marine carbon.

      Put it right by stating the deep ocean holds the vast majority of dissolved inorganic carbon.

    Exam tips

    • Learn approximate values in petagrams of carbon (PgC) or gigatonnes of carbon (GtC) to support comparisons of store sizes.
    • When discussing distribution, link specific stores to geographical biomes, such as the biosphere to tropical rainforests.
    • Use the term 'store' or 'reservoir' rather than 'sink' when referring to the absolute amount of carbon held in these spheres.

    Try the lesson

    The start of the The carbon cycle: Global distribution, and size of major stores of carbon – lithosphere, hydrosphere, cryosphere biosphere, atmosphere. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Which of the following represents the largest global store of carbon?

    Listen

    The global carbon cycle comprises five major stores of varying sizes and distributions. The lithosphere is the largest store, containing over 99.9% of global carbon (approximately 100,000,000 PgC), primarily in sedimentary rocks like limestone and fossil fuels. The hydrosphere is the second largest (approximately 38,000 PgC), with most carbon dissolved in the deep ocean. The biosphere (approximately 3,190 PgC) stores carbon in living vegetation, soils, and peat, distributed heavily in tropical rainforests and boreal forests. The cryosphere stores carbon in permafrost (approximately 1,400 PgC), mainly in tundra regions. The atmosphere is the smallest major store (approximately 750 PgC) but is highly active, distributing carbon globally. A strong answer earns marks for these points. Identify the lithosphere as the largest carbon store, containing sedimentary rocks and fossil fuels. Describe the hydrosphere's role, noting that the deep ocean stores significantly more carbon than the surface ocean. Explain the distribution of the biosphere, highlighting the concentration of terrestrial carbon in tropical and boreal biomes. Recognise the cryosphere as a significant store of frozen organic carbon in permafrost regions. A common slip: Assuming the surface ocean holds the most marine carbon. Instead, stating the deep ocean holds the vast majority of dissolved inorganic carbon. Exam tip: Learn approximate values in petagrams of carbon (PgC) or gigatonnes of carbon (GtC) to support comparisons of store sizes.

    See it

    A top-to-bottom flowchart of the five major carbon stores in order of size. The first node is the lithosphere, described as the largest store, containing over 99.9% of global carbon. An arrow leads down to the hydrosphere, the second largest store. An arrow leads down to the biosphere, storing carbon in living vegetation, soils and peat. An arrow leads down to the cryosphere, storing carbon in permafrost in tundra regions. A final arrow leads down to the atmosphere, the smallest major store but highly active.
    The five major carbon stores ranked from largest to smallest, with the lithosphere the largest and the atmosphere the smallest.

    Put it in order

    Put these steps in the order they happen.

    1. 1. Hydrosphere: second largest store
    2. 2. Biosphere: living vegetation, soils and peat
    3. 3. Lithosphere: largest store, over 99.9% of global carbon
    4. 4. Atmosphere: smallest major store but highly active
    5. 5. Cryosphere: permafrost in tundra regions

    Key words

    Say what each word means before you turn the card.

    Carbon reservoirs

    Try answering aloud or in your head before turning the card.

    Lithosphere

    Try answering aloud or in your head before turning the card.

    Hydrosphere

    Try answering aloud or in your head before turning the card.

    Cryosphere

    Try answering aloud or in your head before turning the card.

    See every definition
    Carbon reservoirs
    Major stores of carbon of varying sizes and distributions, including the lithosphere, hydrosphere, cryosphere, biosphere and atmosphere.
    Lithosphere
    The largest store, containing over 99.9% of global carbon, primarily in sedimentary rocks like limestone and fossil fuels.
    Hydrosphere
    The second largest store, with most carbon dissolved in the deep ocean.
    Cryosphere
    A store of carbon in permafrost, mainly in tundra regions.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 2 boxes numbered instead of named. A top-to-bottom flowchart of the five major carbon stores in order of size. The first node is the lithosphere, described as the largest store, containing over 99.9% of global carbon. An arrow leads down to the hydrosphere, the second largest store. An arrow leads down to the biosphere, storing carbon in living vegetation, soils and peat. An arrow leads down to the cryosphere, storing carbon in permafrost in tundra regions. A final arrow leads down to the atmosphere, the smallest major store but highly active.

    • 1Box 1

    • 2Box 2

    0 of 2 labelled

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