A carbon sink is anything, natural or artificial, that absorbs more carbon from the atmosphere than it releases, and stores some carbon-containing chemical compound for an indefinite period, thereby removing carbon dioxide from the atmosphere. Carbon sinks are a type of carbon pool, which is all the places where carbon can be, including the atmosphere, oceans, soil, plants, and fossil fuels. Carbon sinks are important in understanding the carbon cycle, which is a process that has been perfectly balanced for thousands of years. The ocean, soil, and forests are the worlds largest carbon sinks. Carbon sources, on the other hand, release more carbon than they absorb, and examples of carbon sources include the burning of fossil fuels, deforestation, and volcanic eruptions. Carbon reservoirs are carbon-storing natural features, such as forests or land masses, that exchange carbon with other reservoirs. Mature forests are carbon reservoirs but are not carbon sinks.