Petrology is explained in a brief way to understand about rocks

1. ENGINEERING GEOLOGY
UNIT: 1 INTRODUCTION & WEATHERING OF ROCKS
Importance of Petrology
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2. The study of rocks in all their aspects including
their mineralogies,
textures,
structures (systematic description of rocks in hand specimens);
origin and
their relationships to other rocks is called as
PETROLOGY
PETROLOGY

3. Rocks are divided according to their origin into 3
groups viz.,
IGNEOUS (eg: Granite, Syenite, Charnockite,
Gabbro, Dolerite, Rhyolite),
SEDIMENTARY (eg: shale, sandstone, limestone etc)
and
METAMORPHIC (eg: Quartzite, Marble, Slate etc)

4. IGNEOUS ROCKS

5. Igneous Rocks are formed when hot molten
rock material called magma solidifies (or)
igneous rocks form through
cooling and crystallization of molten rock material

6. If the molten
material is below
the Earth’s surface,
it is called magma or
else it comes out
about the surface ,
it is known as lava

7. The molten material of rock is semi-solid in nature
and consists of liquid , gas and earlier formed
crystals
Molten material also consists of volatiles and
elements like O2, Si, Al, Ca, Na, K, Fe, Mg etc

8. GRANITE
SYENITE
DUNITE
DOLERITE
IGNEOUS ROCKS

9. Importance of igneous rocks

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Granite is used for
kitchen tops,
for construction of monuments,
bridges,
office buildings,
aggregates,
flooring and interior decoration.
Granite looks smooth and shiny when polished and is
used for flooring purpose

11. The weathering and erosion of igneous
rock produces very rich and productive
soils for growing plants
Bath Scrub (Pumice) & Kerb Stone (Granite)

12. Diorite was used
extensively by ancient
civilizations for vases
and other decorative
artwork

13. SEDIMENTARY ROCKS

14. Sedimentary Rocks are formed due to
weathering and erosion of the
pre-existing rocks
Sedimentary rocks are classified on the
basis of the character of the material and
process which leads to its deposition

15. In addition,
the depositional environment plays a
major role in the formation of
sedimentary rocks ie
deposited the material by
wind action or water action

16. Sedimentary rocks
Greywacks arkose sandstone limestone
Chert Conglomerate shales Dolomite
Siltstone Mudstone / claystone Breccia
SANDSTONE GREYWACKE LIMESTONE SHALE

17. Importance of sedimentary rocks

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Sedimentary rocks tell us what the Earth's surface was
like in the geologic past
They contain fossils that tell us about the animals and
plants or show the climate in an area
Sedimentary rocks are also important because they
may contain water for drinking or oil and gas

19. limestone and sand can help us in
making cement,
which is important for foundations
Fuel is one of the major sources of fuel
which comes from coal
Coal is a sedimentary rock that is formed
through compaction of plant debris

20. METAMORPHIC ROCKS

21. Metamorphic rocks are formed through the
transformation of the pre-existing rocks under
increased temperature and pressure conditions
This process of transformation is known as
metamorphism

22. Formation of metamorphic rocks from
pre–existing (igneous or sedimentary) rock is
controlled by the following parameters
Composition of the rock ;
Temperature; Pressure; Chemically active fluids (common fluid is water)
Foliation (under differential stress conditions)
Non-foliation ( under hydrostatic stress )

23. Quartzite Phyllite Marble
Amphibolite Eclogite Schist
Gneiss Khondalite Slate
SCHISTGNEISS

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Quartzite and marble are the most commonly used
for building materials and artwork.
Marble is used for statues and decorative items
Gneiss has many uses as a building
material such as
flooring, ornamental stones,
facing stones on buildings and work
surfaces

25. Slate is a fine-grained, foliated
metamorphic rock that is formed
by the alteration of shale by low-
grade regional metamorphism.
It is popular for a wide variety of
uses such as roofing, flooring,
writing purpose
Slate

26. PETROLOGY is important from civil
engineering point of view because it provides a
proper concept and logical basis for interpreting
certain properties,
structure and
chemical composition of rocks

27. IMPORTANCE OF PETROLOGY

28. Properties reveal the types of rocks which are
suitable for various civil engineering operations
Rocks provide information about the composition
of the Earth and Mantle

29. •The study of petrology is important for a civil engineer
in selection of building stones, road metal etc
•The rocks reflect, either directly or indirectly,
the production and redistribution of heat within the earth
•The study of petrology is fundamental to understand
the large-scale geodynamics of our planet

30. Thank you
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