Rocks and Earth Sciences

21. Which one among the following is NOT a minor plate ?

Which one among the following is NOT a minor plate ?

[amp_mcq option1=”Nazca” option2=”Arabia” option3=”Philippines” option4=”Antarctica” correct=”option4″]

This question was previously asked in
UPSC CAPF – 2015
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The correct answer is D. Antarctica is considered a major tectonic plate, while Nazca, Arabia, and Philippines (Philippine Sea Plate) are generally classified as minor tectonic plates.
The Earth’s lithosphere is broken into several large plates (major plates) and many smaller ones (minor plates) that float on the asthenosphere. There are typically identified as 7 major plates: African, Antarctic, Eurasian, Indo-Australian, North American, Pacific, and South American plates. Minor plates include the Arabian Plate, Caribbean Plate, Cocos Plate, Juan de Fuca Plate, Nazca Plate, Philippine Sea Plate, Scotia Plate, etc.
Major plates are the largest rigid slabs of the lithosphere. Minor plates are smaller sections, often situated between major plates or in complex tectonic regions. The interaction between these plates at their boundaries is the cause of most seismic and volcanic activity on Earth. The Antarctica plate covers the continent of Antarctica and surrounding oceans and is a significant part of the global plate system.

22. Various landforms observed on the surface of the earth are due to the:

Various landforms observed on the surface of the earth are due to the:

  • 1. differences in the type and structure of the crustal material
  • 2. differences in the land forming processes
  • 3. differential rates of the processes at different places on the Earth’s surface

Select the correct answer using the code given below :

[amp_mcq option1=”1 only” option2=”1 and 2 only” option3=”2 and 3″ option4=”1, 2 and 3″ correct=”option4″]

This question was previously asked in
UPSC CAPF – 2015
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The correct answer is D, stating that various landforms are due to all three listed reasons.
– The surface of the Earth is constantly shaped and reshaped by various geological processes.
– **Statement 1 (differences in the type and structure of the crustal material):** Different rock types (e.g., hard granite vs. soft sedimentary rock) and their structure (e.g., folded, faulted, horizontal strata) respond differently to erosional and tectonic forces, leading to varied landforms (e.g., differential erosion creating mesas and buttes).
– **Statement 2 (differences in the land forming processes):** Both endogenic processes (like volcanism, earthquakes, plate movements causing uplift and faulting) and exogenic processes (like weathering, erosion, deposition by rivers, glaciers, wind, waves) create different types of landforms. The presence and dominance of these processes vary globally.
– **Statement 3 (differential rates of the processes at different places on the Earth’s surface):** Even the same processes operate at different intensities and speeds depending on factors like climate, topography, vegetation cover, etc. For example, river erosion rates vary with rainfall, slope, and rock type. These differential rates result in diverse landforms across the globe.
Landform development is a complex interplay of forces originating from within the Earth (endogenic) and those acting on the surface (exogenic). The nature of the material being acted upon and the varying intensity and type of processes across space and time are fundamental controls on landform diversity.

23. Which of the following statements regarding landslides is/are correct?

Which of the following statements regarding landslides is/are correct?

  • 1. They are sudden and sporadic.
  • 2. They result when the slope is gentle.
  • 3. Mining activity is also responsible for landslides.

Select the correct answer using the code given below.

[amp_mcq option1=”1 and 2 only” option2=”1 and 3 only” option3=”3 only” option4=”1, 2 and 3″ correct=”option2″]

This question was previously asked in
UPSC CAPF – 2013
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B) 1 and 3 only
Let’s evaluate each statement regarding landslides:
1. Landslides can be sudden and catastrophic events, occurring without much warning, especially when triggered by intense rainfall or seismic activity. The term “sporadic” also fits, as they are not constant but happen at irregular intervals or locations. While some landslides (like creep) are slow, major destructive landslides are often sudden. This statement is generally correct in describing a common characteristic of significant landslides.
2. Landslides occur when the force pulling material downslope (primarily gravity) exceeds the shear strength of the slope material. This failure is more likely to occur on steeper slopes where the gravitational force parallel to the slope is greater. Gentle slopes are less susceptible to mass movements like landslides, although they can experience very slow forms of movement like creep. Thus, stating that they result when the slope is gentle is incorrect; they are more likely on steeper slopes.
3. Mining activities, such as excavation, blasting, removal of vegetation, changes in drainage patterns, and placement of waste piles, can destabilize slopes and significantly increase the risk of landslides. This is a recognised anthropogenic cause of landslides. This statement is correct.
Based on the analysis, statements 1 and 3 are correct, while statement 2 is incorrect.
Landslides are a type of mass wasting, which is the movement of rock, debris, or earth down a slope due to gravity. Triggers for landslides can be natural (rainfall, earthquakes, volcanic activity) or human-induced (mining, construction, deforestation, irrigation).

24. Which one among the following processes is NOT part of chemical weathe

Which one among the following processes is NOT part of chemical weathering ?

[amp_mcq option1=”Solution” option2=”Hydration” option3=”Reduction” option4=”Thawing” correct=”option4″]

This question was previously asked in
UPSC NDA-2 – 2024
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Thawing is the process of ice melting into water. While it is part of the freeze-thaw cycle, which is a significant process of *physical* weathering, thawing itself is not a chemical reaction that alters the composition of the rock.
– Chemical weathering involves the alteration of the chemical composition of rocks and minerals through processes like dissolution, oxidation, reduction, hydrolysis, hydration, and carbonation.
– Solution: Minerals dissolving in water (e.g., salts, limestone in acidic water).
– Hydration: Minerals absorbing water molecules into their structure (e.g., anhydrite to gypsum).
– Reduction: Gaining electrons; often involves changes in oxidation states of elements like iron, common in anaerobic environments.
– Thawing: The physical change of state from solid (ice) to liquid (water). Freeze-thaw weathering occurs because water expands when it freezes in cracks, exerting pressure that widens the cracks. Thawing allows more water to enter, continuing the cycle, but it is the freezing/expansion that causes mechanical breakdown, not a chemical change during thawing.
Physical weathering breaks down rocks into smaller pieces without changing their chemical composition. Other physical weathering processes include abrasion, exfoliation, granular disintegration, and biological activity (like root wedging). Chemical weathering is more effective in warm and humid climates, while physical weathering is prominent in areas with significant temperature fluctuations and frost action.

25. Which one of the following is correct ?

Which one of the following is correct ?

[amp_mcq option1=”Pyroxene is commonly found in meteorites” option2=”Amphiboles form about 20% of the Earth’s crust” option3=”Quartz is soluble in water” option4=”The word ‘sedimentary’ is derived from the Latin word kelimentum” correct=”option1″]

This question was previously asked in
UPSC NDA-2 – 2024
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The statement that Pyroxene is commonly found in meteorites is correct. The other statements are incorrect.
– Pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rocks. They are also abundant minerals in stony meteorites, particularly in chondrites and achondrites like basalts and dunites originating from asteroids.
– Amphiboles are also common rock-forming silicate minerals, but they constitute a smaller percentage of the Earth’s crust compared to feldspars and quartz. Their abundance is estimated to be around 5-7% of the continental crust.
– Quartz (silicon dioxide, SiO2) is highly insoluble in ordinary water under surface conditions, which contributes to its resistance to chemical weathering. It can be dissolved under extreme conditions (e.g., high temperature and pressure, or presence of specific chemicals), but not in typical rainwater or groundwater.
– The word ‘sedimentary’ is derived from the Latin word ‘sedimentum’, which means “a settling” or “a depositing”.
Feldspars are the most abundant mineral group in the Earth’s crust, making up over 50% by weight. Quartz is the second most abundant mineral in the continental crust. The study of minerals found in meteorites provides valuable insights into the composition and formation of the early solar system and other planetary bodies.

26. Lithosphere consists of

Lithosphere consists of

[amp_mcq option1=”upper and lower mantle.” option2=”crust and core.” option3=”crust and uppermost solid mantle.” option4=”mantle and core.” correct=”option3″]

This question was previously asked in
UPSC NDA-2 – 2019
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C
The Earth’s internal structure can be described in terms of both chemical composition and physical (rheological) properties. The lithosphere is defined by its physical properties; it is the rigid, outermost shell of the Earth. It consists of the crust (both continental and oceanic) and the uppermost, rigid part of the mantle (also known as the lithospheric mantle). It sits atop the asthenosphere, which is a more ductile layer of the upper mantle.
The lithosphere is typically about 100 km thick, though its thickness varies significantly, being thinner under oceanic crust (around 50-100 km) and thicker under continental crust (up to 200 km or more beneath old mountain ranges). The movement of the lithospheric plates over the asthenosphere is the basis of plate tectonics.

27. Which one of the following is a major plate ?

Which one of the following is a major plate ?

[amp_mcq option1=”Pacific Plate” option2=”Cocos Plate” option3=”Arabian Plate” option4=”Philippine Plate” correct=”option1″]

This question was previously asked in
UPSC NDA-2 – 2019
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A
The Earth’s lithosphere is divided into several large tectonic plates. Major plates are the largest ones. The generally accepted list of major plates includes the Pacific Plate, North American Plate, Eurasian Plate, African Plate, Antarctic Plate, Indo-Australian Plate, and South American Plate. The other options listed – Cocos Plate, Arabian Plate, and Philippine Plate – are typically classified as minor or secondary plates due to their smaller size.
There are roughly seven to nine major tectonic plates and numerous minor plates. Major plates cover vast areas, often including both continental and oceanic crust. Minor plates are smaller fragments of the lithosphere. Plate tectonics is the theory describing the large-scale motion of these plates, which is responsible for earthquakes, volcanic activity, mountain building, and ocean basin formation.

28. Stalactite, stalagmite and pillars are the depositional landforms of

Stalactite, stalagmite and pillars are the depositional landforms of

[amp_mcq option1=”running water.” option2=”wind.” option3=”glacier.” option4=”underground water.” correct=”option4″]

This question was previously asked in
UPSC NDA-2 – 2019
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Stalactites, stalagmites, and pillars are depositional landforms typically found in karst topography, which is shaped by the action of underground water dissolving and redepositing soluble rock, primarily limestone.
Stalactites hang from the ceiling of caves, formed by calcium carbonate deposited from dripping water. Stalagmites rise from the cave floor as water drips from above. Pillars are formed when a stalactite and a stalagmite meet.
These features are formed through the process of precipitation of dissolved minerals (calcite) as the water, supersaturated with calcium bicarbonate, loses carbon dioxide upon exposure to the cave air. Underground water is the primary agent responsible for both the dissolution (creating caves) and deposition (forming these structures) in karst regions.

29. In which one of the following folds is the axial plane found to be vir

In which one of the following folds is the axial plane found to be virtually horizontal ?

[amp_mcq option1=”Isoclinal” option2=”Anticlinal” option3=”Recumbent” option4=”Monoclinal” correct=”option3″]

This question was previously asked in
UPSC NDA-2 – 2019
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Folds are bends in layers of rock or sediment. The axial plane is an imaginary plane that bisects the angle between the limbs of the fold and contains the hinge line. In an Isoclinal fold, the limbs are parallel to each other, but the axial plane can be vertical, inclined, or horizontal. An Anticlinal fold is an upward fold, typically with a vertical or steeply dipping axial plane. A Monoclinal fold is a step-like bend. A Recumbent fold is a type of fold where the axial plane is essentially horizontal or nearly horizontal, causing the upper limb to be overturned.
– Recumbent fold: Axial plane is horizontal or near-horizontal.
– Isoclinal fold: Limbs are parallel (axial plane can be any orientation).
– Anticlinal fold: Upward fold (axial plane typically steep).
– Monoclinal fold: Step-like fold.
Recumbent folds indicate significant compressional forces where rock layers have been severely deformed and often transported horizontally over distance (resulting in nappe structures in extreme cases). They are common in intensely deformed mountain belts.

30. Which one of the following is not a process of chemical weathering?

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

[amp_mcq option1=”Solution” option2=”Carbonation” option3=”Oxidation” option4=”Exfoliation” correct=”option4″]

This question was previously asked in
UPSC NDA-2 – 2018
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The correct answer is D) Exfoliation.
Exfoliation is a type of physical weathering process, not chemical weathering. Chemical weathering involves the decomposition of rocks through chemical reactions, such as solution, carbonation, and oxidation.
Chemical weathering processes include Solution (minerals dissolving in water), Carbonation (reaction with carbonic acid, often formed from CO2 in water), Oxidation (reaction with oxygen, e.g., rusting), Hydration (addition of water to mineral structures), and Hydrolysis (reaction of water with minerals to form new compounds). Physical weathering processes, like exfoliation, involve the breakdown of rocks into smaller pieces without changing their chemical composition. Exfoliation is the process where outer layers of rock peel off due to pressure release or thermal expansion/contraction.
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