millions of years
Carbon cycles quickly between organisms and the atmosphere. Cellular respiration releases carbon into the atmosphere as carbon dioxide. Carbon is also released when organisms decompose. Human actions, such as the burning of fossil fuels, also release carbon into the atmosphere. Natural processes, such as volcanic eruptions, release carbon from magma into the atmosphere. Warm ocean waters also release carbon, whereas cold ocean water dissolves carbon from the atmosphere. Photosynthesis autotrophs removes carbon dioxide from the atmosphere and uses it to make organic compounds. Carbon cycles far more slowly through geological processes such as sedimentation. Runoff, rivers and streams dissolve carbon in rocks and carry it to the ocean. Sediments from dead organisms may form fossil fuels or carbon-containing rocks. Carbon may be stored in sedimentary rock for millions of years.