Geography
What are soils
made up of?
Soil
Soils are made
up of:
Humus: organic matter (plants and animals) that
have been decayed.
Air: for example, oxygen, carbon dioxide, nitrogen
(micro-organisms supply nitrogen to the soil in a
soluble form of nitrates.)
Minerals: inorganic matter e.g iron compounds,
silicon
Living organisms: for example, earthworms, bacteria,
fungi
Water and water vapour in soil spaces.
Factors affecting
soil formation:
Weathering
Parent Material (Rock Type)
Climate
Vegetation
Time
How does weathering contribute
to soil formation?
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Weathering breaks down and loosens the
Weathering breaks down and loosens the
surface minerals of rock. Hence, the broken
rocks are transported to another place where it
decomposes and forms soil. The types of
weathering that take place within a region have
a major influence on soil composition and
texture. For example, in a warm climate, where
chemical weathering dominates, soils tend to be
richer in clay.
decomposes and forms soil.
How does the parent material contribute to soil
formation?
How does climate contribute to
soil formation?
How does vegetation and topography
contribute to soil formation?
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Soil can only develop where surface materials remain
in place and are not frequently moved away by mass
wasting. Soils cannot develop where the rate of soil
formation is less than the rate of erosion, so steep
slopes tend to have little or no soil.
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Vegetation plays an important part in the formation
of soils from solid rock. The acids released by the
roots of some plants act to breakdown the rock on
which the soil is forming. The vegetation on a soil is
particularly important in supplying the soil with
precious organic matter.
How does time contribute to soil
formation?
THE END!!!