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3. When this peat is deeply buried, water and other compounds are squeezed out from the
increasing pressure and the lowest quality of coal, lignite, begins for form.
4. Continued burial, resulting in increasing pressures and temperatures, causes this low
quality lignite coal to be transformed into higher quality "black coals". First lignite becomes
sub-bituminous coal, then bituminous coal, and finally the highest quality anthracite coal. As
these transformations occur, the amount of water and other compounds in the coal decreases
and the coal becomes more dense. Along with this comes a higher carbon concentration.
Soil formation:
Figure 24.2 (Soil formation)
Factors affecting soil formation:
Soils form from the interplay of five main factors namely Parent material, Time,
Climate, Relief and Organisms.
Parent material:
This refers to the mineral material, or organic material from which the soil is formed.
Soils will carry the characteristics of its parent material such as color, texture,
structure, mineral composition and so on. For example, if soils are formed from an
area with large rocks (parent rocks) of red sandstone, the soils will also be red in
color and have the same feel as its parent material.
Time:
Soils can take many years to form. Younger soils have some characteristics from
their parent material, but as they age, the addition of organic matter, exposure to
moisture and other environmental factors may change its features. With time, they
settle and are buried deeper below the surface, taking time to transform. Eventually
they may change from one soil type to another.
Climate: