Parent material is the underlying geological material (generally bedrock or a superficial or drift deposit) in which soil horizons form. Soils typically inherit a great deal of structure and minerals from their parent material, and, as such, are often classified based upon their contents of consolidated or unconsolidated mineral material that has undergone some degree of physical or chemical weathering and the mode by which the materials were most recently transported.
Consolidated
Parent materials that are predominantly composed of consolidated rock are termed residual parent material. The consolidated rocks consist of igneous, sedimentary, and metamorphic rock, etc.
Residual
Soil developed in residual parent material is that which forms in consolidated geologic material.
Unconsolidated
This parent material is loosely arranged, particles are not cemented together, and not stratified. This parent material is classified by its last means of transport. For example, material that was transported to a location by glacier, then deposited elsewhere by streams, is classified as stream-transported parent material, or glacial fluvial parent material.
Ice-transported
Glacial till (Morainal)
thumb|A macro photo of basal till parent material|border
thumb|A macro photo of ablation till parent material|alt=A macro photo of ablation till parent material. The right side of the image has a scale bar showing the size of particles from over a centimetre in length, to smaller than a millimetre. The colour of the soil is generally orangeish.
The material dragged with a moving ice sheet. Because it is not transported with liquid water, the material is not sorted by size. There are two kinds of glacial till:
- Basal tillcarried at the base of the glacier and laid underneath it. This till is typically very compacted and does not allow for quick water infiltration.
- Ablation tillcarried on or in the glacier and is laid down as the glacier melts. This till is typically less compacted than basal till.
Glacio-lacustrine
alt=A macro photo of glacio-lacustrine parent material. There are many layers within the photo, called varves, which start as an orange-ish brown and gradually become darker and more grey.|thumb|A macro photo of glacio-lacustrine parent material with clear [[Varve|varves]]
Parent material that is created from the sediments coming into lakes that come from glaciers. The lakes are typically ice margin lakes or other types formed from glacial erosion or deposition. The bedload of the rivers, containing the larger rocks and stones is deposited near the lake edge, while the suspended sediments are settle out all over the lake bed.
Glacio-fluvial
alt=A macro photo of glacio-fluvial parent material. The right side of the image has a scale bar showing the size of particles from over 1cm in length, to smaller than 1mm. The colour of the soil varies from orangeish to blueish-grey.|thumb|A macro photo of glacio-fluvial parent material
Consist of boulders, gravel, sand, silt and clay from ice sheets or glaciers. They are transported, sorted and deposited by streams of water. The deposits are formed beside, below or downstream from the ice.
Glacio-marine
These sediments are created when sediments have been transported to the oceans by glaciers or icebergs. They may contain large boulders, transported by and dropped from icebergs, in the midst of fine-grained sediments.
Water-transported
Within water-transported parent material there are several important types. A macro photo of glacio-lacustrine parent material with clear varves from annual deposition of material.
Alluvium
alt=A macro photo of fluvial parent material. The right side of the image has a scale bar showing the size of particles to be smaller than a centimetre. The colour of the soil is generally blueish-grey with spots of orange.|thumb|A macro photo of fluvial parent material
Parent material transported by streams of which there are three main types. Floodplains are the parts of river valleys that are covered with water during floods. Due to their seasonal nature, floods create stratified layers in which larger particles tend to settle nearer the channel and smaller particles settle nearer the edges of A macro photo of marine parent material showcasing deposition of manganese. Cracks present in the photo are due to drying, but would be massive in the field.the flooding area.