Environmental Geology Lecture Outline - Soils

Two definitions for soil:

What are the initial materials soils are formed from?

What important factors control soil formation? Students should be able to expand a bit on each of the below.

What processes occur during soil formation and what approaches could you take to study these processes? Rephrasing the first question - how does rock turn into soil.

View of weathering pattern in a shallow Tertiary intrusive from the foot of the Chisos Mountains in Big Bend, Texas. Note the rectangular fracture pattern that outline weather blocks. The rock was originally all uniform in color and the banding represents oscillatory iron staining and reflects weathering that worked from the fracture margins into the interior of the blocks. The middle of the blocks are less weathered than the fracture margins. This is the same geometry and process that gives rise to spheroidal boulders when the more weathered material is eroded away.

View of desert soil near Moab, Utah. The reddish material is wind blown fine red sand. The red coloration is due to oxidation of the small bit of iron in the grains. Of distinct interest here is the dark, bumpy covering. To the touch it has a leathery feel, and under the microscope it is a complex community of unicellular plants and organisms called a cryptobiotic crust. This community thrives under the harsh arid desert conditions. It also serves as an important element in soil formation, by trapping sediment, moisture and seeds. The germination of seeds and growth of larger desert plants often depends upon this substrate being developed. Unfortunately the crust doesn't thrive underfoot, and new efforts are being made to educate people about the importance of this cryptobiotic crust to the desert soils and ecosytem.

What are the soil constituents that result from these processes?

What structures (order) exists in soils?

How can soils be classified?


What are environmental concerns associated with soils?

Soil erosion:

Soil salinization:

Nutrient overloading: runoff associated with soil erosion includes dissolved and suspended load material that serve as nutrients for algal growth. This is especially true for urban areas, and for fields were agrichemicals are used. When these standing bodies of water the nutrients can cause algal blooms, oxygen depletion and associated problems. The Mississippi provides enough nutrients to cause algal blooms and what are known as anoxic events in the nearshore Gulf Coast area. One is this is a major disturbance in the Nitrogen cycle.

Engineering concerns


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