Carbon Cycle

The carbon cycle describes the movement of carbon in the atmosphere, where it is in the gaseous form carbon dioxide, through organisms, and then back into the atmosphere and the oceans. Carbon is a central element of the huge diversity of organic chemicals found in living things, such as the many kinds of carbohydrates, proteins, and fats. Energy is contained in the chemical bonds that hold the atoms of carbon and other elements together in these organic compounds. Organisms use chemical energy from organic compounds to carry out all the processes necessary to life.

Carbon is released into the atmosphere through three major processes: cellular respiration, the burning of fossil The carbon cycle. Illustration by Hans & Cassidy. Courtesy of Gale Group. fuels, and volcanic eruptions. In each of these processes, carbon is returned to the atmosphere or to the ocean.

Another way that carbon is released into the atmosphere is through volcanic eruptions. When a volcano erupts, it sends huge amounts of ash and soot high into the atmosphere. Some of this ash and soot is derived from ancient carbon-rich sediments, and the cloud of debris that results from a volcanic eruption returns large amounts of carbon to the atmosphere.