Soils
Soils
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Soil is the loose covering of broken rock particles and
decaying organic matter
Soil is the end result of physical and chemical
weathering.
Soil forms as rock is broken down be weathering and
mixes with other material on the surface.
The longer a soil has been forming, the thicker it is.
Climate has a great affect on soil formation.
Temperature and precipitation play an important role.
How is soil created?
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Decaying organic matter
is called humus.
It is often leaf litter that
is broken down by
decomposers.
Ex. Are ants, worms, etc.
Soil Formation
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During its development, soil forms in
layers vertically.
Solid bedrock from which weathered
pieces of rock first break off is known as
the parent rock.
The weathered material then rests on top
of the parent rock.
Residual vs. Transported
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Residual soil is soil that
comes from the bedrock
that it sits upon.
A transported soil is soil
that has been moved
from a different location
Soil Profile
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A soil profile is a
vertical sequence of soil
layers.
A distinct layer is called
a soil horizon
The three major layers
are: A, B, C
Soil Horizons
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A Horizon- TopsoilSoil rich in humus and
usually dark colored
B Horizon- SubsoilRich in clay minerals
C Horizon- Weathered
bedrock (parent rock).
Texture
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Size of soil particles is soil
texture.
Particles are classified
according to size.
In order from largest to
smallest they are:
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Gravel
Sand is the largest .05- 2 mm
Silt is the middle .0002 - .05
mm
Clay is smallest >.002 mm
Fertility and Color
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Soil Fertility is the
measure of how well a soil
can support plant growth.
A soils’composition and
climate are main factors in
determining its color.
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Red/Yellow= Fe oxidation
Dark Colored= Humus
Gray/Blue= low O2
Loam
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A loam is a soil that is
equal parts of clay, sand
and silt.
It is the best for growing
plants!
Soil Types
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Climactic conditions are
the main influences on
soil development.
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Polar Soil
Temperate Soil
Desert Soil
Tropical Soil