Weathering
can be defined as breaking down of rock into smaller particles to form soil.
There are three types of weathering:
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There are three types of weathering:
1.
Physical
weathering
2.
Chemical
weathering
3.
Biological
weathering
PHYSICAL WEATHERING
Various
agents of physical weathering include:
a.
Temperature: Rock expands when temperature is high during
the day and contrasts at night when the temperature cools down. As a result of
continuous expansion and contraction rock becomes weakened and broken down into
small pieces to form soil
b.
Ice: When water
accumulates in the hollow of a rock the volume increases when water freezes,
this increase forces the rock to expand and the rock contrast when the
temperature is high and some of the water sink into the crack of the rock. when
this continues for a long time the rock becomes weak and disintegrate to form
soil.
c.
Water: Running water do
carry materials such as rock particle, when such particles are rubbed against
one another they further breakdown into smaller pieces to form soil.
d.
Wind: A moving air is
called wind, when air is moving it carries along sand particles. When these sand
particles blow against a rock it breaks down the rock through a gradual process
to form soil.
e.
Human Activities: Human activities
such as road construction, construction of building e.tc. leads to the breaking
down of rocks for use, the unused particles now form soil.
f.
Pressure: Pressure exerted by
human beings or animals on rock is capable of breaking it down to form soil.
CHEMICAL
WEATHERING
This can
be referred to as changes in the composition of rock materials which is brought
about by chemical oxidation.
a. Carbonation: Rain water that passes through atmosphere
combines with Co2 to form a weak acid known as carbonic acid. When
carbonic acid comes in contact with rock especially marble rock it breaks it
down to form soil. C02 + H20 H2C03
b.
Oxidation and
reduction:
Oxidation is the addition of oxygen to a substance while reduction is the
removal of oxygen from a substance. Rock and minerals that contains iron and
manganese are subjects to chemical weathering by oxidation and reduction.
c.
Hydration: This is the
combination of water with another substance and the hydrated substance formed
increases in volume thereby increasing or hasting the weathering process clay
and ironite are hydrated this way:
Fe203 + 3H20 Fe203 3H30
CuS04 + 5H20 CuS04 5H20
d.
Hydrolysis: Water causes reaction in a chemical reaction
with the soil. Water reacts with carbonate and stimulates a double
decomposition type of reaction.
Na2C03 + 2H20 2Na20H + H2C03
3Mg
+ CS0 + 2H20
e.
Solution: Water is able to
dissolve an easy soluble universal in the rock and carry it away through
drainage; if there is no drainage such mineral accumulates to form a
particulars soil.
BIOLOGICAL
WEATHERING
The pressure exerted
on rocks by animals such as elephant, cattle and human beings moving about
causes smaller fragment of rock to disintegrate or breakdown. The activities of
earthworm, termite and other soil organisms have similar effects on the rock.
The root of growing trees may penetrate the cracks in the rock and exert
considerable pressure which leads to the breakdown of the rock.
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