Earth and Space Sciences Regents practice

Earth and Space Sciences Regents, August 2026, question 24

The Model of the Global Carbon Cycle in Gigatons of Carbon (GtC) shows boxes for the amount of carbon stored, in gigatons, and arrows for the amount moved each year, in gigatons per year. Stores: Atmosphere 750; Vegetation 610, Soils and decomposed matter 1580, Total 2190; Surface ocean 1020; Marine life 3; Dissolved organic carbon less than 700; Intermediate and deep ocean 38,100; Surface sediment 150. Arrows: 61.4 and 60.0 between the atmosphere and the vegetation and soils box; 90 from the surface ocean up to the atmosphere and 92 from the atmosphere down to the surface ocean; 5.5 from Fossil fuels and cement production to the atmosphere; 40 and 50 between the surface ocean and marine life; 6 and 4 from marine life; 100 and 91.6 between the surface ocean and the deep ocean; 6 from dissolved organic carbon to the deep ocean; 0.2 from the deep ocean to surface sediment.
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What the figure shows

The Model of the Global Carbon Cycle in Gigatons of Carbon (GtC) shows boxes for the amount of carbon stored, in gigatons, and arrows for the amount moved each year, in gigatons per year. Stores: Atmosphere 750; Vegetation 610, Soils and decomposed matter 1580, Total 2190; Surface ocean 1020; Marine life 3; Dissolved organic carbon less than 700; Intermediate and deep ocean 38,100; Surface sediment 150. Arrows: 61.4 and 60.0 between the atmosphere and the vegetation and soils box; 90 from the surface ocean up to the atmosphere and 92 from the atmosphere down to the surface ocean; 5.5 from Fossil fuels and cement production to the atmosphere; 40 and 50 between the surface ocean and marine life; 6 and 4 from marine life; 100 and 91.6 between the surface ocean and the deep ocean; 6 from dissolved organic carbon to the deep ocean; 0.2 from the deep ocean to surface sediment.

How to think about it

First decide which Earth sphere each box belongs to: atmosphere (air), hydrosphere (water), biosphere (living things and their remains) or geosphere (rock and sediment). Then check each number in the choices. Boxes are amounts stored, arrows are amounts moved per year, and each arrow has a direction, so read the arrowhead before deciding what flows where.

Which statement correctly describes how the cycling of carbon between two Earth spheres is represented in the model?

Topic: Carbon cycling

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