The global carbon cycle and its stores

Overview

Four main carbon stores on Earth, approximate size of the ocean carbon store and carbon sequestration.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Name the four main carbon stores on Earth.

   Model answer

   The lithosphere in rocks and sediments, the oceans, the terrestrial biosphere and soils, and the atmosphere.

2. 2

   Which store holds by far the most carbon?

   Model answer

   Sedimentary rock such as limestone and shale, which holds many millions of billions of tonnes and dwarfs every other store.

3. 3

   State the approximate size of the ocean carbon store.

   Model answer

   In the order of 38,000 billion tonnes of carbon, most of it dissolved in the deep ocean.

4. 4

   How does the atmospheric carbon store compare in size with the ocean store?

   Model answer

   The atmosphere holds under a thousand billion tonnes of carbon, only about a fortieth of the amount held in the oceans.

5. 5

   In what form is most of the ocean's carbon held?

   Model answer

   As dissolved inorganic carbon, mainly bicarbonate ions, in the deep ocean.

6. 6

   Compare the size of the soil carbon store with that of living vegetation.

   Model answer

   Soils hold roughly 1,500 billion tonnes of carbon, around three times as much as is held in living vegetation.

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