Rocks and Earth Sciences

11. Convection currents, which move the tectonic plates, are found in whic

Convection currents, which move the tectonic plates, are found in which layer of the earth?

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Crust
Mantle
Outer core
Inner core
This question was previously asked in
UPSC CAPF – 2021
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The correct answer is B) Mantle.
– Convection currents are driven by heat differences and density variations within a fluid or semi-fluid medium.
– In the Earth’s interior, these currents occur in the mantle, which is primarily solid but behaves plastically over long geological timescales, particularly in the upper part called the asthenosphere.
– The convection in the mantle is the primary driving force behind the movement of the tectonic plates that make up the Earth’s crust.
– The crust is the rigid outermost layer and is moved by the underlying mantle convection.
– The outer core is liquid iron-nickel, but convection here is responsible for generating the Earth’s magnetic field, not directly driving plate tectonics.
– The inner core is solid and extremely hot, but its convection is not relevant to plate movement.

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12. Caves, arches, stacks and stumps are the landscape features of which o

Caves, arches, stacks and stumps are the landscape features of which one of the following?

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River
Wave
Limestone
Wind
This question was previously asked in
UPSC CAPF – 2021
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The correct answer is B) Wave.
Caves, arches, stacks, and stumps are sequential landforms created by the erosional action of waves along coastlines. Waves erode weak points in cliffs, forming sea caves. Over time, two caves on opposite sides of a headland may meet, or a single cave may erode through, forming a sea arch. When the roof of the arch collapses, an isolated pillar of rock, known as a sea stack, is left. Further erosion reduces the stack to a mere stump visible only at low tide.
River erosion creates features like gorges, valleys, meanders, and deltas. Limestone landscapes (karst topography) feature sinkholes, caves (formed by dissolution), and underground drainage. Wind erosion creates landforms such as sand dunes, yardangs, and deflation hollows, primarily in arid environments. The specific sequence of caves, arches, stacks, and stumps is characteristic of coastal erosion by waves.

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13. Which one of the following is not a type of chemical weathering?

Which one of the following is not a type of chemical weathering?

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Carbonation solution
Salt crystal growth
Hydrolysis
Oxidation
This question was previously asked in
UPSC CAPF – 2021
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The correct answer is (B) Salt crystal growth.
Chemical weathering involves the decomposition of rocks and minerals through chemical reactions, such as hydrolysis, oxidation, reduction, solution, and carbonation. Salt crystal growth, also known as salt weathering or crystallization, is a physical weathering process where salts dissolve in water, penetrate rock pores, and crystallize upon evaporation, exerting pressure that causes the rock to disintegrate.
Types of chemical weathering include:
– Carbonation: Reaction of carbonic acid (formed from CO2 dissolved in water) with minerals, especially carbonates.
– Solution: Minerals dissolving directly into water.
– Hydrolysis: Reaction between water molecules and rock-forming minerals, leading to decomposition.
– Oxidation: Reaction of minerals with oxygen, often involving iron-bearing minerals (rusting).
Types of physical weathering include freeze-thaw (frost wedging), exfoliation, thermal expansion/contraction, abrasion, biological activity (root wedging), and salt crystal growth.

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14. Which one of the following karst landforms is the largest in size ?

Which one of the following karst landforms is the largest in size ?

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Polje
Uvala
Swallow Hole
Sink Hole
This question was previously asked in
UPSC CAPF – 2020
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The correct option is A. Among the given options, a Polje is typically the largest karst landform.
– Karst landforms are features created by the dissolution of soluble rocks, primarily limestone.
– A Swallow Hole (Ponor) is a point where surface water disappears underground, typically small in size.
– A Sink Hole (Doline) is a closed depression in the ground surface caused by dissolution or collapse, larger than a swallow hole but generally smaller than uvalas and poljes.
– An Uvala is a compound sinkhole formed by the merging of several dolines, thus larger than a single sinkhole.
– A Polje is a large, flat-floored depression in a karst region, often elongated and bounded by steep walls. They can be several kilometers long and wide and are the largest karst depressions.
Karst topography is characterized by features like sinkholes, caves, disappearing streams, and underground drainage systems. The size of karst landforms varies significantly depending on the scale and intensity of the dissolution processes.

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15. A long narrow stretch of sand and/or shingle with one end attached to

A long narrow stretch of sand and/or shingle with one end attached to the mainland is called

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Sand spit
Sand bar
Sand dune
Tombolo
This question was previously asked in
UPSC CAPF – 2020
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A long narrow stretch of sand and/or shingle with one end attached to the mainland is called a sand spit.
A spit is a depositional landform found along coasts, formed by the deposition of sediment carried by longshore drift. It extends from the land into the sea, often with a curved or hooked end.
A sand bar is a submerged or partially submerged ridge of sand. A sand dune is a hill of sand formed by wind. A tombolo is a spit or bar connecting an island to the mainland or to another island.

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16. Match List I with List II and select the correct answer using the code

Match List I with List II and select the correct answer using the code given below the Lists :

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List I
(Landform)		List II
(Agent)
A. Loess1. Wind deposited
B. Tombolo2. Glacier deposited
C. Point bars3. River deposited
D. Moraines4. Sea deposited

Code :

1 4 3 2
1 3 4 2
2 3 4 1
2 4 3 1
This question was previously asked in
UPSC CAPF – 2019
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The correct matching of landforms with the agents responsible for their deposition is as follows:
A. Loess is a fine, unconsolidated deposit of wind-blown silt, hence it is wind deposited. (Matches with 1)
B. A Tombolo is a spit or bar that connects an island to the mainland or to another island, typically formed by wave action and deposition in the sea. (Matches with 4)
C. Point bars are crescent-shaped accumulations of sand and gravel deposited on the inside bend of a meandering river. They are formed by river deposition. (Matches with 3)
D. Moraines are accumulations of glacial debris (till) deposited by a glacier, typically forming ridges, mounds, or plains. They are glacier deposited. (Matches with 2)
Thus, the correct code is A-1, B-4, C-3, D-2.
– Loess is an aeolian (wind-driven) deposit.
– Tombolos are coastal features formed by marine deposition.
– Point bars are fluvial features formed by river deposition.
– Moraines are glacial features formed by glacial deposition.
Landforms are natural features of the solid surface of the Earth. Geomorphic agents like wind, water (rivers, seas), and ice (glaciers) are responsible for the erosion, transportation, and deposition of material, leading to the formation of various landforms.

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17. Which one of the following is NOT a palaeoclimatic geological indicato

Which one of the following is NOT a palaeoclimatic geological indicator ?

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Lacustrine deposits
Ice sheets and ice cores
Evaporite deposits
Sedimentary deposits
This question was previously asked in
UPSC CAPF – 2019
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The correct answer is D) Sedimentary deposits. While many types of sedimentary deposits are excellent palaeoclimatic indicators (such as lacustrine deposits, evaporites, tills, coal seams, etc.), the term “Sedimentary deposits” itself is too general. Not all sedimentary deposits provide clear palaeoclimate information, and it is the specific characteristics or type of sedimentary deposit that makes it an indicator, unlike the other options which represent specific types of deposits known to be valuable palaeoclimate proxies.
– Palaeoclimatic geological indicators are geological features, structures, or deposits that contain evidence about past climate conditions.
– Lacustrine deposits (lake sediments) often preserve pollen, microfossils, and sediment layers that reflect changes in precipitation, temperature, and vegetation.
– Ice sheets and ice cores contain trapped gases, isotopes, and impurities that provide high-resolution records of past atmospheric composition and temperature.
– Evaporite deposits (e.g., salt, gypsum) form in environments with high evaporation rates, indicating arid or semi-arid conditions.
– Sedimentary deposits encompass a vast range of rocks and unconsolidated sediments formed by deposition. While climate influences many sedimentary processes and products, some sedimentary deposits are formed primarily by tectonic or erosional processes without a strong, direct, or easily interpretable climate signal. The term is too broad to be a specific indicator type in the same way as the others listed.
Specific types of sedimentary rocks like glacial till (indicating past glaciation), coal (indicating warm, humid, swampy conditions), loess (wind-blown silt indicating arid/semi-arid conditions), and certain marine sediments are indeed used as palaeoclimate indicators. However, “Sedimentary deposits” as a general category is not a specific indicator type itself.

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18. Springs are common in which of the following areas? 1. Well jointed

Springs are common in which of the following areas?

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  • 1. Well jointed rocks
  • 2. Arid areas with underlying rocks
  • 3. Karst topography
  • 4. Tilted strata

Select the correct answer using the code given below.

1 and 3 only
1, 3 and 4
2 and 4
3 and 4 only
This question was previously asked in
UPSC CAPF – 2018
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Springs are common in areas with well-jointed rocks, karst topography, and tilted strata.
Springs occur where groundwater flows out onto the surface. This typically happens in areas where geological conditions facilitate the movement and emergence of groundwater.
1. **Well-jointed rocks:** Fractures and joints act as conduits for groundwater flow, allowing water to reach the surface. (Correct)
2. **Arid areas with underlying rocks:** Arid conditions generally mean low precipitation, low groundwater recharge, and deep water tables, making springs less common than in humid regions. (Incorrect)
3. **Karst topography:** Limestone or other soluble rocks are dissolved by groundwater, creating caves, sinkholes, and extensive underground drainage systems. Springs, often large ones (karst springs), are characteristic features of karst landscapes as groundwater emerges from these systems. (Correct)
4. **Tilted strata:** Layers of permeable rock (aquifers) between impermeable layers can become confined aquifers when tilted. If the impermeable upper layer is breached (e.g., by erosion or a fault), the pressurized water in the aquifer can rise to the surface as an artesian spring. (Correct)
The location and flow rate of springs are influenced by factors such as precipitation, aquifer properties, land use, and geological structures.

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19. Which of the following statements concerning the circum-pacific belt a

Which of the following statements concerning the circum-pacific belt are correct?
1. It is an active volcanic realm
2. It is an active seismic realm
3. It is a divergent plate boundary
4. It is prone to Tsunami
Select the correct answer using the code given below:

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1 and 2 only
3 and 4 only
1, 2 and 4 only
1, 2, 3 and 4
This question was previously asked in
UPSC CAPF – 2016
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The correct option is C) 1, 2 and 4 only.
The Circum-Pacific Belt, also known as the Ring of Fire, is a major area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur. This high activity is due to the presence of numerous plate boundaries, primarily convergent ones, where tectonic plates are colliding or subducting.
Let’s evaluate each statement:
1. **It is an active volcanic realm:** Correct. The Ring of Fire contains a vast majority of the world’s active and dormant volcanoes.
2. **It is an active seismic realm:** Correct. It is the most seismically active region globally, experiencing frequent and powerful earthquakes.
3. **It is a divergent plate boundary:** Incorrect. While there are some segments of divergent boundaries (like the East Pacific Rise) and transform boundaries within or connected to the Ring of Fire, the dominant type of plate interaction responsible for the intense volcanism and seismicity in most parts of the belt is **convergent**, involving subduction zones. Divergent boundaries are typically associated with mid-ocean ridges.
4. **It is prone to Tsunami:** Correct. Tsunamis are often triggered by large underwater earthquakes, volcanic eruptions, or landslides, particularly those associated with subduction zones found along convergent plate boundaries like those prevalent in the Ring of Fire.
Therefore, statements 1, 2, and 4 are correct, while statement 3 is incorrect.

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20. Which one among the following plains is associated with Limestone Topo

Which one among the following plains is associated with Limestone Topography ?

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Bajada plain
Alluvial plain
Karst plain
Pene plain
This question was previously asked in
UPSC CAPF – 2015
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Limestone topography is also known as Karst topography. It is a landscape formed from the dissolution of soluble rocks, such as limestone, dolomite, and gypsum. Characteristics of karst topography include sinkholes (dolines), caves, underground drainage systems, and the absence of surface rivers or lakes over large areas. A plain developed in such a region would be termed a Karst plain, often featuring numerous sinkholes or other dissolution features.
Karst landscapes are specifically associated with the chemical weathering (dissolution) of soluble bedrock, most commonly limestone.
Bajada plains are formed by the coalescing of several alluvial fans along the base of a mountain front in arid or semi-arid regions. Alluvial plains are level landform areas built by deposition of sediment by rivers. Peneplains are low-relief plains that form over long periods as a result of erosion wearing down highlands, often approaching a base level. None of these are primarily defined by limestone dissolution processes.

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