Therefore there must be another mechanism. One process by which carbon dioxide is removed from the atmosphere is rock weathering, where rainwater and carbon dioxide combine with rocks to form carbonates. Lovelock, Margulis and others discovered that the process is greatly accelerated by the presence of soil bacteria. The carbonates are washed away into the ocean, where microscopic algae use them to make tiny shells. When the algae die, their shells sink to the bottom of the ocean, forming limestone sediments.
Limestone is so heavy that it gradually sinks underneath the Earth's mantle, where it melts.
Eventually some of the carbon dioxide contained in the limestone will be fed back into the atmosphere through another volcano. Since the soil bacteria are more active in high temperatures, the removal of carbon dioxide is accelerated when the planet is hot. This has the effect of cooling the planet. Therefore the whole massive cycle forms a feedback loop. Lovelock and Margulis identified a number of other feedback loops which operate in a similar way.