Slow carbon cycle

• Define residence time

  the length of time that a molecule of water or carbon dioxide etc remains in natural storage (eg atmosphere or oceans)
• How much carbon is circulated by the SCC?

  Between 10 - 100 million tonnes a year
• What is the residence time for carbon held in rocks

  150 million years
• How are carbon rich sedimentary rocks created?

  CO2 diffuses from the atmosphere into oceans.

  Marine organisms make their shells and skeletons by fixing dissolved carbon with calcium to form calcium carbonate.

  When they die their remains sink to the ocean floor

  They accumulate and over millions of years heat and pressure convert them into carbon rich sedimentary rocks.
• What do fossil fuels as well as deep-ocean sediments act like?

  carbon sinks