Earth

Types of soil and classification

The soil covers approximately a third of the whole Earth’s surface, with a thickness that ranges from tens of metres to a minimum of few centimetres, according to the intensity and duration of the rock changing processes. The factors that are responsible for soil formation create different types of soil in large geographic areas and inside small regions. The soil, in fact, is different in each area of the world: each area has its own climate, rocks and vegetation and, therefore, its own soil, with unique characteristics. You can find some examples on the images. There are many methods to classify the soil. They all aim at organizing the different types of soil according to determined criteria, based either on a paedogenesis factor or on another specific characteristic of the soil. Although there are many links between the different official classifications, it would be useful to have one international classification, which is valid for all countries. Among the main soil classifications, we can mention the American Agricultural Department classification (U.S.D.A.), F.A.O. (United Nations Organization for agriculture and food in the world), and U.N.E.S.C.O. (United Nations Organization for education, science and culture).