The slow carbon cycle and the sea

The idea

Over millions of years buried organisms become fossil fuels, whose burning releases their carbon as CO2 quickly; oceans absorb CO2 as carbonate and bicarbonate ions, taken up by phytoplankton and shell-formers, and store carbon on the ocean floor.

Coal and oil

Coal, oil and gas are burnt for cooking, heating and travel.

Where did the carbon in them come from, and how long did it take?

• Dead plants and animals, over millions of years
• From the Sun directly, in a day
• From the sea in one year

Buried, burnt, dissolved

Press Next step.

Slow to make, quick to burn

Fossil fuels take millions of years to form, but burning returns their carbon to the air as CO₂ very quickly. The ocean also takes in CO₂ from the air, and some of that carbon is stored on the ocean floor for a long time.

Over millions of years buried organisms become fossil fuels, whose burning releases carbon as CO₂ quickly. Oceans absorb CO₂ as carbonate and bicarbonate ions, used by phytoplankton and shell-formers, and store carbon on the ocean floor.

Notes

The slow cycle turns buried organisms into fossil fuels over millions of years; burning returns CO₂ quickly. Oceans absorb CO₂ as carbonate and bicarbonate ions and store carbon on the ocean floor.

Check yourself

Over what time do dead plants and animals become fossil fuels?

When fossil fuels are burnt, on what time scale is the carbon released as CO₂?

In what form does ocean water hold CO₂ that it absorbs from the atmosphere?

What happens to the organic matter of marine organisms that die?

• Millions of years — correct. Yes!
• Days to years. Days to years is the time scale of the fast carbon cycle.
• A single season. Fossil fuels form from buried organisms over millions of years.
• Millions of years. Fossil fuels took millions of years to form, but their carbon is released as CO₂ on a very short time scale.
• A very short time scale — correct. Yes!
• The same time it took to form them. Burning releases the carbon much faster than the time it took to form the fuels.
• Coal and oil. These are fossil fuels in the geosphere.
• Glucose in the air. The ocean water absorbs atmospheric CO₂ to form carbonate and bicarbonate ions.
• Carbonate and bicarbonate ions — correct. Yes!
• They sink to the ocean floor and the matter is stored as carbon for a long period — correct. Yes!
• It is burnt at once. The chapter says it is stored as carbon for a long period on the ocean floor.
• It rises into the atmosphere as CO₂ at once. The chapter says dead organisms sink to the ocean floor and their organic matter is stored as carbon for a long period.