What happens in a soil? Soil system science.

A soil from a system perspective: The diagram below attempts to capture some of what happens in soils. The different combination of conditions and associated processes makes for a great diversity of soils.

In the above diagram, put a star next to all the components that may be a function of climate. What does this tell you about one important factor in classification.

Soil zonation: A zonation develops in the soil due to the movement of materials by vertical water movement and due to the concentration of organic activity at the top. The exact character of the zonation is a function of the variables above, including climate and time. The diagram below shows the three zones often distinguishable.


Soil classification is very complex. It helps to understand, because different environmental problems are typically associated with the different soil types as we will see.

University of Idaho site on the 12 orders of soil classification. Looking at this classification, what are the two critical factors in classification.

For our purposes I would like you to be familiar with four of the 12 soil orders - histosols, oxisols, aridisols, and mollisols. You should be familiar with several characteristics of each soil type.


Soil erosion

What are rates of erosion? How would you measure?

What are mechanisms of erosion?

What is human activity the promotes soil erosion?

Effect of plumes of sediment on aquatic ecosystems.

Possible solutions to soil erosion?

Website with nice summary of soil erosion, including some good images.
Engineering concerns related to soils.

Differential compaction (settling):

Swelling clays:

Soil creep.

Piping - subsurface erosion of fine soils, common in loess.

Drainage characteristics, especially for sewage tile fields.

Permafrost, associated with cryosols:


Harmon D. Maher Jr. reserves copyrights to the materials in this site. Material may be used for non-profit educational purposes as long as proper attribution is given. For permission for any other use please contact author. Thank you.