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III. Soil Formation

III. Soil Formation. Soil is an important natural resource because it is essential to life on earth! It is found almost everywhere on earth. Soil is the loose covering of broken rock particles and decaying organic matter, called hums, overlying the bedrock of earth’s surface.

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III. Soil Formation

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  1. III. Soil Formation Soil is an important natural resource because it is essential to life on earth! It is found almost everywhere on earth.

  2. Soil is the loose covering of broken rock particles and decaying organic matter, called hums, overlying the bedrock of earth’s surface. It’s the result of mechanical and chemical weathering and biological activity over long periods of time!

  3. Burrowing animals, insects, bacteria, and fungi help add organic matter to soil

  4. During development, soil forms in layers

  5. Parent Rock The solid bedrock from which weatherized pieces of rock first break off

  6. Residual Soil • Soil located above the parent material.

  7. Transported Soil Has been moved to a location away from its parent bedrock.

  8. Soil Profiles A soil profile is the vertical sequence of soil layers.

  9. Topography • The topography of a region affects the thickness of developing soil. • In sloped areas, where runoff readily occurs, the coarser particles of soil remain on the slopes. • The smaller particles move downslope.

  10. Soil Horizons A distinct layer, or zone within a soil profile is called a soil horizon. There are 3 major soil horizons: A, B, and C

  11. Soil Types • Polar • Temperate • Desert • Tropical

  12. Polar Soil • Form at high latitudes (Canada, Antarctica) • Have good drainage • Shallow(only a few cm. deep) • Permafrost (frozen ground) is usually found beneath it.

  13. Temperate Soil • Vary greatly • Supports environments such as forests, grasslands, and prairies. • Annual rainfall greater than 50-60 cm

  14. Desert Soil • Receives low levels of precipitation. Less than 25 cm per year. • Has high levels of salts, light colored, and coarse • Supports only a limited amount of vegetation • Little or no organic matter • Very thin A horizon • Has abundant nutrients

  15. Tropical Soil • Found in High temperatures • Heavy rainfall • Weathered and infertile soil

  16. Soil Textures • Particles of soil are classified according to size as being: clay, silt, or sand. • Clay is the smallest • Sand is the largest • Look at pg. 172 in book at Table 7-2 and pg. 173 Figure 7-24.

  17. Soil Fertility Is the measure of how well a soil can support the growth of plants.

  18. Factors that affect soil fertility are: • Availability of minerals and nutrients • Number of microorganisms present • Amount of precipitation available • Topography • The level of acidity

  19. Soil Color 1. A soil’s composition and the climate in which it develops are main factors that determine the soil color. 2. Topsoil is usually dark-colored because it is rich in humus.

  20. Soil Color Continued.. • Color cannot predict fertility. • Red and yellow soils may be the result of oxidation of iron and minerals. • Grayish or bluish soils are common in poorly drained regions where soils are constantly wet and lack oxygen.

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