For a long time, it was believed that the ground beneath our feet was generally void of any living organisms.
Life is known to exist on the surface and in the uppermost soil layers.
This region of life forms the biosphere. Within the last decade, however, geologists have found substantial populations of bacteria deep below the earth's surface. Evidence for the existence of life below the surface came during the late 1980's, when scientists began examining deep core samples. Both geologists and biologists are slowly improving their understanding about the role of bacteria and other life forms below the surface. This knowledge will be important in developing effective and practical solutions to cleaning up contaminated soils and groundwater.