TECTONICS, WEATHERING, EROSION AND SOILS - Physical Geography - page 69

Geography Reference

In-Depth Information

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Figure 3.4 A common classification for soil texture.

Chemical properties of soils

Soil chemical properties are strongly influenced by parent material

and organic matter content which provides an amount of tiny clay

and organic particles. Clay minerals are formed from the weather-

ing products of aluminium and silicate minerals. As clay minerals

are small, a volume of clay will have a large surface area around all

of its particles in total compared to the same volume of sand. To

test this out, measure the surface area of three soccer balls that fill a

box and then measure the surface area of the number of tennis or

golf balls it takes to fill the same box. An ion is an atom or group

of atoms with an electrical charge (either positive or negative).

Clay particles have a negative electrical charge so these ions can

attract and hold water and cations (positively charged particles).

Therefore, they have a fundamental influence on both the physical

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