Soils

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Soils
Soil Composition
Comparing Soil Types
Soil and Roots
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Ecosystem
Living and non living things and their
interactions
Ecology
The study of the Ecosystem
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What is soil made of?
Weathering of parent rock
Organic material
Open spaces
Water
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All soil originates from parent rock. Parent rock
is broken down by weathering into small mineral
particles. The sizes of the mineral particles
determine the texture of the soil. One way of
classifying soils is by their texture.
Particles larger than 2 mm are called gravel. Par
ticles between 2 mm and 0.05 mm are called
sand. Particles between 0.05 mm and 0.002 mm are
called silt. Particles less than 0.002 mm
are called clay. Soil made up of a mixture of
all three sizes of particles is called loam
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Soil Defined
Soil is the total mixture of mineral particles of
many sizes, organic matter, open spaces, water,
and salt solutions in a defined structure.
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Formation of Soil
Parent Rock begins to break down into smaller and
smaller pieces.
Organic matter (dead plant and animal material)
accumulates at the surface
Over time the weathering process forms soil at
deeper levels and the layer of soil on the top
becomes thicker.
As separate layers of soils become identifiable
they are known as Horizons
Horizon A is known as topsoil
Horizon B is known as subsoil
Horizon C most closely resembles parent rock
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All of the Horizons together are known as a soil
profile
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Although different locations and types of parent
material will form soils at varying rates, it is
believed to take centuries to form a complete
profile
Some scientists believe that it takes 200 to 300
years to form one centimeter of soil form parent
rock and some well formed soil profiles can be
hundreds of centimeters thick.
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How do roots effect soil?
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Sources

1. Pictures provided by Google Images
2. Fast 1 Curriculum University Hawaii
3. General Science A Voyage of Adventure, Chapter
   20 Soils Prentice Hall 1989