The Canadian System of Soil Classification divides Canada's soil types into ten categories based on dominant characteristics and their formation processes. Each soil type is defined as an Order. Beneath each Order is a Great Subgroup, which delineates formative processes within each Order. Particularly important in all forms is the horizon, any given layer in the soil parallel to the ground's surface that possesses traits differing from horizons above and below. The Vertisolic, Cryosolic, Organic, Solonetzic and Podzolic Orders involve varying horizon traits.
Vertisolic Order soils contain a minimum of 60 percent clay, half of which is smectite. This gives the soils marked shrink-swell tendencies, creating a thick mire when saturated with water and a hard surface with deep, wide cracks when dehydrated. Major areas of Vertisolic soils appear in the grasslands of western Canada's interior plains. Cross-section identification requires that both slickenside and vertic horizons be present. Slickensides are irregularly shaped points of confluence between multiple separate horizons, while vertics display vertical cracks in the deep soil containing materials from the soil's surface.
Cryosolic Order soils are any form of organic or mineral soil that is frozen 1 meter or less from the surface. In soils with heavily mixed horizons due to heavy tectonic activity, this limit is increased to 2 meters. Because of Canada's distance from the equator, its upper one-third is composed entirely of Cryosolic soils.
Organic Order soils are primarily, though not entirely, located in lowland areas with poor drainage and high water tables. They equate to what we commonly call peat, muck, fen or bog. To be soil of the Organic Order, the soil must contain a minimum of 17 percent carbon from organic sources, equating to 30 percent organic matter by weight. While some other orders meet this requirement, the organic matter must extend through horizons a minimum of 40 cm below the surface, congruent with roughly 1,000 years of development.
Solonetzic Order soils were developed under grass and light-forest cover found throughout much of Canada's lowland plains. Though commonly found near Podzolic Order soils, Solonetzic soils retain their individuality because of their solonetzic B horizons. In other words, the layer of soil directly beneath the surface is very hard when dry and extremely sticky when wet. Also, the layer beneath that typically has a very high salt content; it is called a saline C horizon.
Podzolic Order soils are found beneath coniferous forests. They are mildly acidic, stay moist year-round and have a silty texture. They are distinguished by a B horizon that's a minimum of 10 cm thick containing deposits of decaying plant matter interspersed with nuggets of aluminum and oxidizing iron. Thanks to the rusting iron, this horizon starts out deep red and becomes progressively more yellow the deeper you dig.