The lithosphere of Earth comprises the crust and the uppermost mantle. The lithosphere consists of separate tectonic plates. The uppermost part of the lithosphere has undergone chemical and physical processes to form a soil layer called the pedosphere. The pedosphere is vital to life on Earth and an intrinsic part of all terrestrial ecosystems. The pedosphere provides a substrate for primary producers, i.e., plants, which are in turn vital for all other life on Earth. The pedosphere is also a vital part of the hydrological cycle, as groundwater feeds streams and soil and groundwater is taken up by plants.