We begin by establishing what is a soil. In the most general sense, a soil is a collection or accumulation of disintegrated rock fragments whose particle sizes can range from boulders measuring up to a few metres in dimension to much lesser sizes generally called soil, with particle sizes ranging somewhere close to 100 mm to sizes that cannot be seen by the naked eye-less than 0.0001 mm (in the micrometre range). Disintegration of rock produces fragments commonly referred to by the public as boulders, stones, gravel, sand, and clay-most often distinguished or characterized by particle (fragment) sizes, with the largest ones being stones and the smallest ones being clay. The forces and agents responsible for rock disintegration include mechanical, chemical, biologically mediated, and hydraulic.