The Nature of the Soil

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The Nature of the Soil
Soil is the natural surface layer that contains
both inorganic weathered debris and living
matter. Soils are developed over a long period of
time through the combination of physical,
chemical, and weathering processes. The upper O
and A horizons usually contain the most organic
matter. Debris is moved down the profile
producing distinct layers or horizons.
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The Nature of the Soil
Exposure of the solum and regolith beneath it,
Little Tesque Creek, near Santa Fe, New Mexico.
An idealized diagram showing soil profile with
soil horizons.
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Soil Horizons
Most soils possess soil horizons distinctive
horizontal layers that differ in physical
composition, chemical composition, or organic
content or structure.
A column of soil will normally show a series of
horizons.
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Soils of the World
The soils of the world are classified into
groups, orders and suborders. The following map
shows the major areas of occurrence of the soil
orders. The soil orders and suborders are
correlated with global climate zones.
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Soils of the World
Key Boralfs Spodosols Tundra
Soils Udalfs Oxisols Highland
(Icesheet) Ustalfs Vertisols Xeralfs
Mollisols Ultisols Aridisols
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