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1
SoilsSoil is made up of a number of different layers.
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Different Layers of Soil
Upper layer (O) known as litter
Topsoil layer (A) contains humus
Subsoil layer (B) stones mixed with some humus
Bedrock (C)
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Layers of Soil
Litter Layer
Topsoil Layer
Subsoil Layer
Bedrock
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Layers of Soil
Litter Area on top of soil
contains leaves, dead plants and organisms.
Reduces water loss Limits changes in
temperature
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Layers of Soil
Topsoil Humus Layer….Plants
and decaying animal matter
Roots of plants Small particles of rock Darker in color
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Layers of Soil
Subsoil More rocks than topsoil Less humus than
topsoil Lighter in color
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Layers of Soil
Bedrock Solid rock found
beneath subsoil Can be seen at the
surface if other layers are washed away
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Groundwater Versus Surface Water
Groundwater…water which moves down through the soil.
Surface water... water which runs on the ground and collects in lakes, ponds and oceans
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Percolation
Process which happens when surface water is pulled downward by gravity to form ground water.
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Leaching
Occurs when water dissolves and takes nutrients from the soils.
Occurs during percolation Takes nutrients from plants leaving soils
more infertile
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pH of Soils
Soils can be acidic (pH less than 7)Soils can be basic (pH greater than
7)Soils can be neutral
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Factors affecting pH of soils
Type of rock Alkaline minerals in
rocks can cause high pH’s
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Factors affecting pH of soils
Type of Plants Decaying plants can
cause soils to have lower pH levels and become acidic.
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Factors affecting pH of soils
Burning of fossil fuels
When acid rain enters the soil it lowers pH.
Takes nutrients from the topsoil.