The term "soil" has many definitions, depending upon who is using the term. For example, to engineers "soil" is unconsolidated surficial material, whereas to many soil scientists it is mainly the medium for plant growth. A definition of soil that serves our purpose well is a slight modification of that given by Joffe'": a soil is described as a natural body consisting of layers or horizons of mineral and/or organic constituents of variable thicknesses, which differ from the parent material in their morphological, physical, chemical, and mineralogical properties and their biological characteristics; at least some of these properties are pedogenic (Fig. 1-1). Soil horizons generally are unconsolidated, but some contain sufficient amounts of silica, carbonates, or iron oxides to be cemented <...>
