Soil is the thin, fragile surface layer of Earth. It is a dynamic, loose and porous body of variable thickness (between a few centimetres and a few metres). Soil is formed by continuous transformations of rock or deposit through physical, chemical and biological processes. It is one of the two main components of Earth — the other being oceans — in which life is particularly active. Soil is the source and site of many human activities, and human life greatly depends on it. In Canada, agricultural, environmental and natural-resource scientists are at the forefront of research on soil.