Download Soil Formation

SOIL
Kim Lachler
NCES: 6.E.2.3 & 2.4
Updated 11/11/14
Soil Composition
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Consists of:
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Weathered rock
Decayed organic matter
Mineral fragments
Water
Air
Soil Composition
Organic Matter
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Majority of it is dead vegetation
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Rest is dead animals and micro-organisms
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Humus
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is dark material made from organic matter
provides nutrients for plants
Soil Composition
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There are spaces
between the particles of
soil
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When the soil is dry they
are filled with air
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When the soil is wet they
are filled with water
Soil Texture
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The size of the particles of the rocks and minerals
makes up the texture.
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Clay  Silt  Sand  Gravel  Rock
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Clays feel sticky.
Silt feels smooth.
Sand feels gritty.
Loam soil
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a soil with roughly equal proportions of sand, silt, and clay.
Soil Profile
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Soil Profile
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Horizons
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Is made up of all the
layers of soil
What the layers of soil
are called
Most soil profiles have
3 horizons
Soil Profile
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A horizon
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Also known as topsoil
Top layer
May be covered with litter (leaves, twigs, etc)
Soil Profile
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B horizon
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Middle layer
Lighter in color
Less fertile (less nutrients)
Has the most leached material
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Leaching –
when minerals are dissolved in water in the A horizon and
carried down by the water to the B horizon.
Soil Profile
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C Horizon
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Bottom horizon
Made from weathered rock
Contains little leaching or organic matter
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What is under the C Horizon?
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Bed rock
Soil Formation
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There are 5 factors that
affect soil formation
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Climate
Parent material
Vegetation
Slope
Time
Soil Formation
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Climate
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Dry climates have less
organic matter thus
thinner soils than wetter
climates
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Cold climates also have
less organic matter thus
thinner soils the
temperate climates
Soil Formation
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Vegetation
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Areas with lots of vegetation like prairies and
forest have more organic matter, therefore richer
top soils
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Richer top soils encourage more vegetation growth
so which came first?
Soil Formation
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Parent rock
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The minerals that make
up the bedrock is what
determines the minerals
in the soil.
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This will affect the type
of vegetation
Soil Formation
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Slope
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Since gravity pulls things down hill
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Soils near the top of a slope are thinner
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Soils near the bottom of a slope are thicker
Soil Formation
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Time
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The longer the bed rock has been weathered the
more minerals will be in the soil.
Bibliography
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Glencoe
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Google images, soil, www.googleimages.com, accessed 11/21/2011
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Google images, humus soil, www.googleimages.com, accessed 11/21/2011
Google images, leaching soil, www.googleimages.com, accessed 11/21/2011
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Colorado state University Extension, CMG garden notes, http://www.ext.colostate.edu/mg/gardennotes/214.html, accessed 11/11/14