40. Geography for NDA / CDS / AFCAT

• 0 Questions answered correctly
• 0 Questions answered incorrect
• 10 Questions unattempted

• 1

  Match the following : 

  	A.	Mantle		1.	Heavy rocks of lithosphere
  	B.	Sima		2.	Layer below earth's crust
  	C.	Sial		3.	Light rocks of lithosphere
  	D.	Bill		4.	Small peninsula

   

  • A

    A B C D

    3 1 4 2

  • B

    A B C D

    4 3 2 1

  • C

    A B C D

    2 1 3 4

  • D

    A B C D

    1 2 3 4

  Explanation

  Answer: (c) 2 1 3 4

  Explanation:

  A. Mantle (2): The mantle is the layer beneath the Earth's crust, extending to a depth of about 2,900 kilometers. It is composed mainly of silicate rocks rich in iron and magnesium.

  B. Sima (1): 'Sima' refers to the lower layer of the Earth's crust, predominantly composed of rocks rich in silica and magnesium. These are denser, forming the oceanic crust.

  C. Sial (3): 'Sial' denotes the upper layer of the Earth's crust, rich in silica and aluminum. These lighter rocks constitute the continental crust.

  D. Bill (4): A 'bill' is a term used to describe a small peninsula, a landform projecting into a body of water.

  Incorrect Options:

  (a) 3 1 4 2: This suggests Mantle = Light rocks of lithosphere, which is incorrect; the mantle is beneath the crust.

  (b) 4 3 2 1: This matches Mantle = Small peninsula, which is incorrect; the mantle is a geological layer, not a landform.

  (d) 1 2 3 4: This matches Mantle = Heavy rocks of lithosphere, which is partially correct but doesn't accurately describe the mantle's position below the crust.

• 2

  The term ‘rock’ comprises :

   

   

  • A

    (a)  an aggregate of minerals, usually two or more

     

  • B

    (b)  a naturally occurring mass of solid, inorganic or organic

     

  • C

    (c)  forming a firm and coherent mass of the earth’s crust

     

  • D

    (d) all of the above

  Explanation

  Answer: (d) all of the above

  Explanation:

  (a) an aggregate of minerals, usually two or more: Rocks are typically composed of multiple minerals aggregated together.

  (b) a naturally occurring mass of solid, inorganic or organic: Rocks are natural solid masses that can be inorganic (e.g., granite) or contain organic material (e.g., coal).

  (c) forming a firm and coherent mass of the earth’s crust: Rocks constitute the solid and coherent mass forming the Earth's crust.

  Since all statements accurately describe rocks, option (d) is correct.

• 3

  The most ideal conditions for the chemical weathering are found in :

   

   

  • A

    (a) cold and dry regions

     

  • B

    (b) cold and humid regions

     

  • C

    (c) hot and dry regions

     

  • D

    (d) hot and humid regions

     

  Explanation

  Answer: (d) hot and humid regions

  Explanation:

  Chemical weathering is most effective in hot and humid climates because high temperatures and abundant moisture accelerate chemical reactions that break down rocks. 

  Incorrect Options:

  • (a) cold and dry regions: These conditions slow down chemical reactions, making chemical weathering less effective.
  • (b) cold and humid regions: While moisture is present, low temperatures inhibit chemical reactions.
  • (c) hot and dry regions: High temperatures are present, but the lack of moisture limits chemical weathering.
• 4

  Which of the following predominantly acts as the agent of chemical erosion of soil ?

   

   

  • A

    (a) Glacier

     

  • B

    (b) Seawave

     

  • C

    (c) Underground water

     

  • D

    (d) Wind

     

  Explanation

  Answer: (c) Underground water

  Explanation:

  Underground water can cause chemical erosion through processes like dissolution, where soluble minerals are dissolved, leading to features like sinkholes and caves. 

  Incorrect Options:

  • (a) Glacier: Glaciers primarily cause physical erosion through abrasion and plucking.
  • (b) Seawave: Seawaves mainly cause physical erosion through the mechanical action of waves.
  • (d) Wind: Wind causes physical erosion by transporting and abrading particles, known as deflation and abrasion.
• 5

  Which of the following is a chemical weathering process ?

   

   

  • A

    (a) Frost Action 

     

  • B

    (b) Hydraulic Action

     

  • C

    (c) Oxidation

     

  • D

    (d) Thermal Expansion

     

  Explanation

  Answer: (c) Oxidation

  Explanation:

  Oxidation is a chemical weathering process where minerals, especially those containing iron, react with oxygen to form oxides, leading to the breakdown of the rock. 

  Incorrect Options:

  • (a) Frost Action: This is a physical weathering process where water freezes in cracks, expands, and causes the rock to break apart.
  • (b) Hydraulic Action: This refers to the physical process of water eroding rock, not a chemical weathering process.
  • (d) Thermal Expansion: This is a physical weathering process where temperature changes cause rocks to expand and contract, leading to disintegration.
• 6

  What is Weathering ?

   

   

  • A

    (a) Removal of earth’s material by river action

     

  • B

    (b) Removal of earth’s material by wind action

     

  • C

    (c) Breaking up and disintegration of rocks

     

  • D

    (d) Hardening up of rocks due to weather conditions

  Explanation

  Answer: (c) Breaking up and disintegration of rocks

  Explanation:

  Weathering refers to the process by which rocks are broken down into smaller particles through physical disintegration, chemical decomposition, or biological activity, without the removal of material.

  Incorrect Options:

  • (a) Removal of earth’s material by river action: This describes erosion, specifically fluvial erosion, not weathering.
  • (b) Removal of earth’s material by wind action: This describes aeolian erosion, not weathering.
  • (d) Hardening up of rocks due to weather conditions: This is not related to weathering; in fact, weathering leads to the breakdown, not hardening, of rocks.
• 7

  The Himalayas are formed due to :

   

   

  • A

    (a) internal pressure of two large land forms

     

  • B

    (b) faulting of the earth’s crust

     

  • C

    (c) folding of the earth’s crust

     

  • D

    (d) folding of the geo-syncline named Tethys

     

  Explanation

  Answer: (d) folding of the geo-syncline named Tethys

  Explanation:

  The Himalayas were formed from the collision between the Indian Plate and the Eurasian Plate. This collision caused the sedimentary rocks in the Tethys geosyncline, a vast marine basin, to fold and uplift, leading to the creation of the Himalayan mountain range. 

  Incorrect Options:

  • (a) internal pressure of two large land forms: While tectonic pressures are involved, the specific process was the collision and subsequent folding of the Tethys geosyncline sediments.
  • (b) faulting of the earth’s crust: Faulting involves the breaking and displacement of rocks along fractures, which is not the primary process responsible for the formation of the Himalayas.
  • (c) folding of the earth’s crust: This is partially correct, but it lacks the specificity of the Tethys geosyncline's role in the formation of the Himalayas.
• 8

  Molten rock below the surface of the earth is called :

   

   

  • A

    (a) Basalt      

  • B

     (b) Laccolith

     

  • C

    (c) Lava          

  • D

     (d) Magma

  Explanation

  Answer: (d) Magma

  Explanation:

  • Magma: Magma is molten rock located beneath the Earth's surface.

  Incorrect Options:

  • (a) Basalt: Basalt is an extrusive igneous rock formed from the rapid cooling of lava at the surface.
  • (b) Laccolith: A laccolith is a dome-shaped intrusive igneous body formed from magma that has intruded between rock layers.
  • (c) Lava: Lava is molten rock that has erupted onto the Earth's surface.
• 9

  Which metal is most abundant in the earth's crust ?

   

   

  • A

    (a) Calcium    

  • B

    (b) Magnesium

     

  • C

    (c) Aluminium 

  • D

     (d) Iron

  Explanation

  Answer: (c) Aluminium

  Explanation:

  • Aluminium: Aluminium is the most abundant metal in the Earth's crust, constituting about 8.23% by weight.

  Incorrect Options:

  • (a) Calcium: Calcium makes up approximately 4.15% of the Earth's crust.
  • (b) Magnesium: Magnesium accounts for about 2.33% of the Earth's crust.
  • (d) Iron: Iron constitutes roughly 5.63% of the Earth's crust.
• 10

  In which type of rocks are coal and petroleum found ?

   

   

  • A

    (a) Granite       

  • B

    (b) Igneous

     

  • C

    (c) Metamorphic   

  • D

     (d) Sedimentary

  Explanation

  Answer: (d) Sedimentary

  Explanation:

  • Sedimentary Rocks: Coal and petroleum are formed from the accumulation and compaction of organic material over geological timescales, processes that occur in sedimentary environments.

  Incorrect Options:

  • (a) Granite: Granite is an igneous rock, formed from the cooling of magma, and does not contain fossil fuels.
  • (b) Igneous: Igneous rocks form from solidified magma or lava and typically lack the organic material necessary for coal and petroleum formation.
  • (c) Metamorphic: Metamorphic rocks arise from the transformation of existing rock types under heat and pressure, conditions not conducive to the formation of coal and petroleum.