Parent Material

In British Columbia as well as most of Canada, the majority of soils have developed from deposits left on the earth’s surface by the last glacial period that ended about 10,000 years ago. The nature of the parent material strongly influences soil properties such as texture, pH, fertility, and mineralogy. For example, coarse-grained, quartz-rich parent material such as glacial outwash generates soils that are often gravely and with a coarse (sandy) texture.

Soil parent material may be broadly grouped into the following classes:

1. Residual or sedentary – developed in place (in situ) from the underlying rock. Typically it experienced long and intense weathering. Residual parent materials can be found overlying any rock type – provided that the landscape has been stable for a sufficient period of time for weathering to occur. This situation and type of parent material are uncommon in Canada.
2. Transported – loose sediments or surficial materials (i.e., weathering products of rocks that are not cemented or consolidated) that have been transported and deposited by gravity, water, ice, or wind. These materials are classified on the basis of the agents responsible for their movement and deposition (see table below).
3. Cumulose – organic deposits that have developed in place from plant residues and have been preserved by a high water table (or some other factor retarding decomposition). These deposits are widespread and not restricted to any climatic zone. Examples include peat (undecomposed or slightly decomposed organic matter) and muck (highly decomposed organic material).