Download 8-Weathering of Rocks - sir cr reddy college

SAI TEJA.P
1st B.sc MPG
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Weathering of rocks is constant and it destroy the
rocks.
weathering is the breaking down of rocks ,
soils and minerals
weathering produces rocks waste are transported
are called EROSION
Weathering is of two types
1)Mechanical (or) Physical weathering
2)Chemical weathering
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In this type of weathering the rocks are break
and disintegrate
They loose broken material will be angular in
shape
In mechanical (or) physical weathering is three
types:a)Thermal Weathering
b)Exfoliation
c)Frost Action
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Thermal weathering is by a sudden breaking rocks
by temperature changes
More common in diserts areas because temperature
changes rapidly
And also forest fires and lightning will weathering
the rocks
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Rocks breaking along the joints .The joints are
breaking will be parallel to the surface.
Slowly rocks will fall down layers by layers.
This will produce large dome like structure
called EXFOLIATION DOMES.
Rocks and boulders will show rounded form
called SPHEROIDAL WEATHERING.
Exfoliation joints have modified the nearsurface portions of massive granitic rocks
in Yosemite National Park
Exfoliation joints in granite at
Enchanted Rock State Natural Area,
Texas, USA
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River water enters the cracks and joints of the
rocks. This water will freeze during the night.
Frozen water will create pressure and
temperature and increase the cracks.
Frost action is common in high areas (Hill
stations & Gardens) exposed to rain and snow.
A rock in Abisko, Sweden fractured by mechanical frost
weathering or thermal stress
Chemical weathering is done by rain water.
Chemical weathering will decompose and form
solutions.
 Chemical weathering changes the chemical
composition of the mineral.
EX:-Felspar mineral changes to clay mineral.
 It depends on composition of original material and
depth of the mineral.
 This weathering is by the process of
SOLUTIONS, OXIDATION, HYDRATION, AND
FORMATION OF CARBONATES.
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Comparison of unweathered (left)
and weathered limestone. (right)
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River water will have carbon-dioxide which
reacts with minerals.
EX:-CALCIUM MINERALS & IRON OXIDE etc…,
Carbonates changes into bi-carbonates.
solutions will fall down.
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It is the chemical composition with oxygen.
Water having oxygen will react with iron
minerals.
Solutions are formed and FERROUS IRON
changes into FERRIC IRON.
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Hydration is the chemical reaction with water.
Water removes soluble material by
LEACHING.
Some chemical reactions form HYDROUS
OXIDE & HYDROUS SILICATES.
Water reaction will bring another change called
HYDROLYSIS
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Erosional features formed due to weathering.
Atmospheric conditions like temperature, wind
directions, rain water will form different
features. They are bad lands, cuestas, misas,
buttes, hogbacks etc..,
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End product of weathering is soils. There are
different types of soils LATERITIC SOIL,
SANDY SOIL, BLACK COTTON SOIL,
LOAMY SOIL, CLAYEY SOIL, PEAT SOIL
etc…,
Lateritic soil, Black soil, Peat soil are good for
agriculture.
Loamy soil and sandy soil are not good for
agriculture.
Mr .
P.C. Swaroop sir
Department of Geology