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Outcomes

Students will:

  • Investigate the characteristics and formation of surface geology, specifically soil.
  • Differentiate soil profiles across Canada, and understand the mechanical, chemical, and biological processes that contribute to their formation.
Key Terms

Humic Material
Mesic Material
Peat
Permafrost
Plate Tectonics
Soil Horizons


What is a Soil Profile?

A soil profile is a vertical cross section of the ground. Soil profiles can show distinct or indistinct layers called soil horizons (see Figure 11). Soil profiles can be used to quickly compare ground characteristics between different locations and to assess whether or not a location is suitable for tasks such as farming.


Figure 11 shows a deep soil profile with a few distinct horizons. Image by Mike Kolman.

Figure 12 shows distinct soil horizons. Original image by HolgerK.


What is a Soil Horizon?

Soil horizons form through a variety of physical, biological, and chemical processes that impact varying materials to at different depths within the soil. These processes include weathering, erosion, leaching, eluviation, illuviation, acidification, (de)calcification, (de)salinization, decomposition, mineralization, and many others. A few examples of these processes are listed below.

How do Soil Horizons Form?

Soil horizons form through a variety of physical, biological, and chemical processes that selectively move around materials to various depths within the soil. These processes include weathering, erosion, leaching, eluviation, illuviation, acidification, (de)calcification, (de)salinization, decomposition, mineralization, and many others. A few examples of these processes are listed below.

  • Physical
    • Water flowing down horizons will transport solid and dissolved materials to lower horizons through eluviation and leaching respectively.
    • Weathering and erosion in the soil will break down rocks, altering the texture and appearance.
  • Biological
    • Decomposing materials introduce new nutrients into the topsoil that will eventually make its way into lower horizons.
    • Plants absorb nutrients out from the upper layers of soil, changing the soil chemistry and possibly colour, depending on the nutrients remaining.
  • Chemical
    • Acidic solutions in the water can react with minerals and rocks, altering the appearance, texture, and chemistry of that horizon.
    • Leaching can remove salts and calcium, among many other chemicals and elements, which alters the appearance, texture, and chemistry of the soil.


Soil Profiles Across Canada
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