Understanding Soil Formation

Five different factors that affect soil formation

2. Topography - the slope characteristics of the soil

1. Parent material - type of rock material from which the soil is formed

What are five different factors that affect soil formation?

3. Living organisms4. Time or weathering5. Climate

- the temperature and moisture characteristics of the area

Types of Parent Material• Most soils in Illinois have been formed from

material originally moved by glaciers.

Types of Parent Material

• About 64% of the soil in Illinois has been formed from loess.

• occurred from the blowing of the soil after the glaciers melted and dried

• most desirable single soil parent material – well-balanced mineral content– medium texture– excellent water-holding capacity

Types of Parent Material

• About 16% of the soil in Illinois has been formed from outwash.

• occurred when the glaciers melted

Types of Parent Material

• About 11% of the soil in Illinois is from glacial till.

• not layered• Pebbles and various sizes of boulders

Types of Parent Material

• 7% of the soil in Illinois is a result of recent sediments deposited by streams as they flood and is referred to as alluvium.

Types of Parent Material• Most of the shale, sandstone, or limestone

bedrock in Illinois is buried by loess, glacial till, outwash, or alluvium.

• About 2% of the soils in Illinois

Types of Parent Material

• Less than 1% of the soils in Illinois are classified as organic.

• occur where formerly shallow ponds supported swamp vegetation

• peat and muck– Muck is more decomposed than peat.

Other Factors

• Topography refers to the slope characteristics of a soil.

• It includes the degree or steepness, length, shape, and direction of a slope.

Other Factors

• Organisms that live in soil (i.e., plants, insects, and microbes) actively affect soil formation.

• The greatest affect on the development of soil is from plants that once grew in it, which is referred to as native vegetation

Other Factors• There are two types of weathering.

1. Physical weathering is caused by the effects of climatic factors (e.g., temperature, water, and wind).

2. Chemical weathering changes the chemical makeup of rock and breaks it down.