A soil profile is a vertical section of the soil continuum that extends from the surface through various horizons to parent material, consolidated substrate or unconsolidated material to a selected depth.

Most soil profiles have three major horizons called the surface horizon, the subsoil, and the substratum. Each horizon differs in colour, texture, structure, reaction, consistency, mineral and chemical composition, and arrangement in the soil profile.

Because of the inherent lateral and vertical variability of the soil continuum it is necessary to describe the soil profile across a given range of values and properties in each of horizon. This allows the soil profile to be classified and also allows interpretation of the limiatations to .

Information about a soil profile of interest can be obtained using soil pits, existing vertical exposures, relatively undisturbed soil cores or auger boring. The most preferable way is from a soil pit or relatively undisturbed vertical exposure. What is also necessary is information about the site. This gives the reader of the soil profile information a better understanding as to the development of the soil profile.

In addition, soil samples can also be collected and taken back to the laboratory for chemical and physical analysis.  terraGIS contains raster files of the spatial distribution of some of the more important soil property information collected at various depths (i.e. 0-0.30, 0.30-0.60, 0.60-0.90 and 6-12 m).  The soil property information that can be viewed includes:

• Texture (e.g. clay, silt and sand),
• Chemistry (e.g. pH, ECe),
• Cations (e.g. Ca and Mg),
• Stability (e.g. ESP and ESI), and
• Hydrology (e.g. Hydraulic conductivity and Available Water Content)

In the following section a brief introduction is provided on each of these soil properties to enable easier interpretation of the data shown in terraGIS.