DOWNLOAD MOBILE APPLICATION TO LEARN MORE: ROCK AND MINERALS FOR SSC CHSL
DOWNLOAD MOBILE APPLICATION TO LEARN MORE: ROCK AND MINERALS FOR SSC CHSL
DOWNLOAD MOBILE APPLICATION TO LEARN MORE: ROCK AND MINERALS FOR SSC CHSL
A rock is a natural mass of minerals found within the earth’s crust while minerals are substances that have a definite chemical composition and occur freely in nature.
Rocks can be are classified in three types on the basis of their texture and the process of formation i.e. igneous, sedimentary and metamorphic rocks. The igneous rocks are formed when molten lava from a volcano cools down. These rocks are also known as primary rocks as they are the first to be formed and are further of two types: extrusive and intrusive.
Extrusive igneous rocks are formed when magma flows out on to the earth’s surface and cools down rapidly by air to form solid fine-grained rocks. Intrusive igneous rocks are formed when molten magma cools down inside the earth’s crust.
Sedimentary rocks are formed by the sedimentation or deposition of smaller rock particles in layers called beds or strata. The smaller particles formed from these large rocks are called sediments.
Sometimes, during formation, sedimentary rocks may contain preserved remains of plants and animals trapped within the layers. These remains are called fossils.
Metamorphic rocks are formed when igneous and sedimentary rocks undergo great heat and pressure over time.
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DIFFERENT ROCK TYPES
Many different kinds of rocks are classified into three families based on their mode of formation.
Classification of Rocks:
| Igneous Rocks | Solidified from magma and lava |
| Sedimentary Rocks | The result of the deposition of fragments of rocks by exogenous processes |
| Metamorphic Rocks | Formed out of existing rocks undergoing recrystallization |
IGNEOUS ROCKS
- It is formed out of magma and lava from the interior of the earth.
- They are also known as primary rocks.
- When magma in its upward movement cools and turns into a solid form it is called igneous rock.
- The process of cooling and solidification can happen in the crust of the earth or on the surface of the earth.
- Igneous rocks are classified based on texture.
- If the molten material is
- Cooled slowly at great depths, mineral grains may be very large.
- Sudden cooling at the surface results in small and smooth grains.
- Intermediate conditions of cooling would result in intermediate sizes of grains making up igneous rocks.
- Granite
- Gabbro
- Pegmatite
- Basalt
- Volcanic
- Breccia
- Tuff
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SEDIMENTARY ROCKS
- Rocks of the earth’s surface area exposed to denudation agents and are broken up into various sizes of fragments.
- These fragments are carried by various exogenous agencies and deposited.
- These deposits through compaction turn into rocks. This process is called lithification.
- In several sedimentary rocks, the layers of deposits maintain their characteristics even after lithification.
- Sandstone, shale are some of the examples for Sedimentary Rocks.
- Depending upon the mode of formation, sedimentary rocks are categorized into three groups:
- Mechanically formed
- Eg: Sandstone, conglomerate, limestone, shale, loess, etc.
- Chemically formed
- Eg: Chert, limestone, halite, potash, etc.
- Organically formed
- Eg: Geyserite, chalk, limestone, coal, etc.
- Mechanically formed
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METAMORPIC ROCKS
- These rocks form under the action of volume, pressure, and temperature (PVT) changes.
- Metamorphism happens when rocks are forced down to lower levels by tectonic processes or when molten magma rising through the crust comes in contact with the crustal rocks or the underlying rocks are exposed to great amounts of pressure by overlying rocks.
- The materials of rocks chemically modify and recrystallize due to thermal metamorphism.
- There are two types of thermal metamorphism
- Contact metamorphism
- Regional metamorphism
- The rocks come in contact with hot intruding magma and lava and the rock materials recrystallize under high temperatures.
- The rocks experience recrystallization due to deformation caused by tectonic shearing together with high temperature or pressure or both.
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Table of Contents
ROCK AND MINERALS FOR SSC CHSL
1. A non-metallic mineral in the following minerals is
A. silver
B. copper
C. zinc
D. coal
2. Igneous rocks are
A. primary rocks
B. secondary rocks
C. tertiary rocks
D. soft rock
3. Which one of the following is the component of sand and granite?
A. Amphibole
B. Quartz
C. Pyroxene
D. Mica
4. The most abundant rocks found on the earth’s crust are
A. igneous rocks
B. sedimentary rocks
C. metamorphic rocks
D. granite rock
5. Rocks that were originally either sedimentary, igneous, or metamorphic and have been changed further by heat and pressure are called:
A. Volcanic
B. Sedimented
C. Metamorphic
D. None of the above
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6. Which one of the following is not a sedimentary rock?
A. Tillite
B. Borax
C. Breccia
D. Marble
7. Iron is a
A. ferrous metal
B. non-ferrous metal
C. precious metal
D. non-precious metal
8. What kind of colour does Pyroxene consist of?
A. Green
B. Black
C. Both A. and B.
D. None of the above
9. The minerals that do not contain metal contend are known as
A. precious minerals
B. ferrous minerals
C. non-metallic minerals
D. non-ferrous minerals
10. The parent material of soils is derived from
A. Igneous rocks
B. Metamorphic rocks
C. Sedimentary rocks
D. Biological action
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11. Coals and petroleum found in _________ types of rocks.
A: Granite rock
B: Igneous rock
C: Metamorphic rock
D: Sedimentary rock.
12. Which metal is the most abundant in the earth’s crust?
A: Iron
B: Zinc
C: Aluminium
D: Magnesium
13. What the molten rock is known when it stays under the surface of earth?
A: Lava
B: Magma
C: Basalt
D: Ignite
14. When molten rock comes out the surface of earth, it is known as –
A: Lava
B: Magma
C: Laccolith
D: Metamorphic
15. How the Himalayas are formed?
A: due to pressure of two large landform.
B: due to weakness of the earth crust
C: due to folding of the earth crust.
D: due to folding of the geosyncline named Tethys.
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16. Which process is known as chemical weathering process?
A: Expansion due to thermal energy
B: Frost action
C: Oxidation and Reduction
D: Hydraulic action.
17. The breakdown of minerals due to the decaying vegetation producing organic acid is called-
A: Biological weathering
B: Degradational weathering
C: Chemical weathering
D: Physical weathering
18. Wadi a kind of valley has occurred
A: at hot desert with occasional heavy rainfall.
B: at high mountain range where precipitation is high.
C: at the beach where enough sand exists.
D: at the polar region when ice starts to melt.
19. Which one of the following are the two main constituents of granite?
A. Iron and nickel
B. Iron and silver
C. Silica and Aluminium
D. Iron Oxide and potassium
20. Science of rocks is known as
A. Mineralogy
B. Mineral Science
C. Petrology
D. Iron ology
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ALSO VISIT: GEOGRAPHY
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ANSWERS:
| 1.d 2.a 3.b 4.a 5.c 6.d 7.a 8.d 9.c 10.c | 11.d 12.c 13.b 14.a 15.d 16.c 17.c 18. a 19.c 20.c |
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