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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.