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Teacher Information!
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Necessary materials:
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PowerPoint Guide
Soil Formation
Pgs 46-50 in Ch.4 of Managing Our Natural Resources
Soil and Water Resources
Students will be able to…
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Discuss how soil is formed.
Describe weathering processes.
Soil
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Geologic definition: Loose surface of the
earth as distinguished from solid bedrock
(support of plant life not required).
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Traditional definition: Material which
nourishes and supports growing plants
(includes rocks, water, snow, air).
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Organic + Inorganic material
Soil
 Mixture
of inorganic matter (mineral),
organic matter, water, and air.
Air 25%
Mineral Matter
45%
Water 25%
Organic Matter 5%
% Soil components varies:
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Type of vegetation
Amount of mechanical compaction
Amount of soil water present.
Soil matters
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Inorganic matter
 Rock slowly broken down into small
particles
Organic matter
 Decaying plants and animals
 Decomposers are vital!
Soil formation is slow!
Parent material
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Minerals
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Examples?
Rocks
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Aggregates of minerals
Three types
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Igneous
Sedimentary
Metamorphic
More parent material
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Glacial deposits
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Loess deposits
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Windblown silt
Eastern Mississippi Valley soils
Alluvial and marine deposits
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Common in the Midwest U.S.
Water-borne sediments
Organic deposits
Weathering forces
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Rocks & minerals break down 
smaller pieces
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Temperature changes
Water action
Plant roots
Ice expansion
Mechanical grinding
Organic Matter
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Only about 5% of most soils
Small proportion but very important
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WHY is organic matter important?
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Organic Matter
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Decayed plants and animals
Two types
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Original tissue—still recognizable
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Humus—matter is too decomposed 
unrecognizable
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Examples?
Examples?
WHAT causes decomposition?
Review
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Discuss how soil is formed.
Describe weathering processes.