Rocks and Earth Sciences Archives

41. Consider the following features about a geographical phenomenon : 1.

Consider the following features about a geographical phenomenon :

1. Torrents of snow and ice roaring down a steep mountain side
2. It is hazardous to skiers and mountaineers
3. It involves a mix of falling, rolling, sliding and flowing of materials

Which of the following phenomena can be identified with the above features?

Slump and earthflow

Avalanche

Landslide

Rockslide

This question was previously asked in

UPSC NDA-1 – 2022

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The description of “Torrents of snow and ice roaring down a steep mountain side” is characteristic of an avalanche. Avalanches are rapid mass movements composed mainly of snow and ice. They are a significant hazard in mountainous regions, particularly for skiers and mountaineers. The movement in an avalanche often involves a mix of falling, rolling, sliding, and flowing snow/ice and debris.

An avalanche is a specific type of rapid mass wasting involving snow and ice on a slope.

While landslides can involve rock, debris, or earth, the mention of “snow and ice” specifically points towards an avalanche. Rockslides involve primarily rock material. Slumps and earthflows are types of mass movements involving soil and unconsolidated material, usually less rapid and not primarily composed of snow and ice.

42. Which of the following statements in respect of landslides are correct

Which of the following statements in respect of landslides are correct?

These occur only on gentle slopes during rain.
They generally occur in clay-rich soil.
Earthquakes trigger landslides.

Select the correct answer using the code given below.

1 and 2 only

1 and 3 only

2 and 3 only

1, 2 and 3

This question was previously asked in

UPSC NDA-1 – 2022

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Statement 1 is incorrect because landslides occur primarily on steep slopes where gravity is a significant factor, not only on gentle slopes. While rain is a common trigger, landslides can occur due to other factors as well. Statement 2 is correct as clay-rich soils become unstable when saturated, increasing the risk of landslides. Statement 3 is correct as earthquakes are well-known triggers for landslides due to ground shaking.

Landslides are mass movements occurring on slopes. Their occurrence is influenced by factors like slope angle, soil/rock type, water content, and external triggers like rain or earthquakes.

Factors contributing to landslides include geological factors (weak materials, jointing), morphological factors (steep slopes, erosion), physical factors (intense rainfall, seismic activity), and human factors (deforestation, construction). Clay soils are particularly prone to landslides due to their low shear strength when wet.

43. While travelling to a hilly region, you notice a massive boulder, whic

While travelling to a hilly region, you notice a massive boulder, which was loosened by heavy rains and moved downhill. This has resulted due to which of the following processes?

Mass wasting
Erosion
Weathering

Select the correct answer using the code given below.

1 only

1 and 2 only

2 and 3 only

1, 2 and 3

This question was previously asked in

UPSC NDA-1 – 2022

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The scenario describes a process involving multiple geological phenomena. Heavy rains contribute to weathering by saturating the ground and potentially expanding cracks, which helps *loosen* the boulder or the material supporting it. Heavy rains also act as a trigger for mass wasting by increasing the weight of the material, reducing friction (lubrication), and increasing pore water pressure. Erosion by the heavy rain could also potentially undercut the boulder’s support. The actual *movement* of the boulder downhill under the influence of gravity is a clear example of mass wasting (potentially a rockfall or part of a landslide). Thus, weathering contributed to the loosening, erosion by rain contributed to the triggering mechanism, and mass wasting is the process of movement.

Weathering weakens material, making it susceptible to movement. Mass wasting is the downslope movement under gravity. Erosion is the transport of material by agents like water. In this scenario, all three processes are likely involved or contribute to the event.

Mass wasting events like landslides or rockfalls are often preceded by weathering and triggered by events like heavy rainfall or earthquakes. Heavy rain can cause significant erosion, which further destabilizes slopes and contributes to the trigger.

44. A large body of magmatic material that cools in the deeper depth of th

A large body of magmatic material that cools in the deeper depth of the Earth’s crust and develops in the form of large domes is known as

Batholiths.

Lacoliths.

Lopoliths.

Phacoliths.

This question was previously asked in

UPSC NDA-1 – 2021

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A Batholith is a very large body of intrusive igneous rock (pluton) that forms when molten rock (magma) cools and solidifies beneath the Earth’s surface. Batholiths are the largest type of intrusive igneous features.

Batholiths are typically irregular in shape and can extend over vast areas (hundreds or thousands of square kilometers) and to significant depths. They are formed by multiple intrusions of magma over millions of years and are characteristic of convergent plate boundaries where mountain building occurs.

Laccoliths are mushroom-shaped or lens-shaped intrusions that have pushed overlying rock layers upwards into a dome. Lopoliths are basin-shaped or saucer-shaped intrusions. Phacoliths are lens-shaped intrusions parallel to the bedding planes in folded strata. While laccoliths form domes, batholiths fit the description of a “large body… cools in the deeper depth… develops in the form of large domes” (often exposed by erosion as large areas of igneous rock).

45. Basket-of-eggs topography is related to

Basket-of-eggs topography is related to

Drumlins.

Eskers.

Cirques.

Moraines.

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UPSC NDA-1 – 2021

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The correct answer is Drumlins.

“Basket-of-eggs topography” is a descriptive term used for landscapes characterized by a large number of drumlins. Drumlins are streamlined, elongated hills formed by glacial ice acting on underlying unconsolidated material. They are typically shaped like an inverted spoon or half-buried egg, with the blunt end facing upstream (towards the ice flow) and the tapered end pointing downstream. When numerous drumlins are present together in a region, they create a distinctive pattern resembling a basket filled with eggs from an aerial view.

Eskers are ridge-like deposits left by meltwater streams within or under a glacier. Cirques are bowl-shaped depressions carved by glacial erosion at the head of a valley. Moraines are accumulations of rock debris deposited by glaciers, forming various features like ridges (lateral, medial, terminal moraines) or irregular deposits (ground moraine). Only drumlins occur in clusters that create the “basket-of-eggs” appearance.

46. The process whereby certain minerals absorb the water, expand and chan

The process whereby certain minerals absorb the water, expand and change is called as

Hydration.

Oxidation.

Hydrolysis.

Carbonation.

This question was previously asked in

UPSC NDA-1 – 2021

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The correct answer is Hydration.

Hydration is a process of chemical weathering where certain minerals absorb water into their crystal structure. This absorption causes the minerals to swell and expand, leading to stress within the rock and eventual disintegration. Examples include the hydration of feldspars into clay minerals.

Oxidation is a process where minerals react with oxygen, often in the presence of water, leading to rust formation in iron-bearing minerals. Hydrolysis involves the chemical reaction of water with a mineral, breaking down the mineral by replacing ions with hydrogen or hydroxyl ions from water. Carbonation is the reaction of minerals with carbonic acid (formed when carbon dioxide dissolves in water), common in the weathering of limestone. While water is involved in all these processes, the specific process of mineral absorption of water leading to expansion and change is defined as hydration.

47. Advantage(s) of tectonic activity in Iceland include(s): 1. Source o

Advantage(s) of tectonic activity in Iceland include(s):

1. Source of natural geothermal energy
2. Creation of new land
3. Attraction of tourists

Select the correct answer using the code given below :

1 only

2 and 3 only

1 and 3 only

1, 2 and 3

This question was previously asked in

UPSC NDA-1 – 2021

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The correct answer is D) 1, 2 and 3.

Iceland is located on the Mid-Atlantic Ridge, a divergent plate boundary, making it one of the most geologically active places on Earth. This tectonic activity manifests as frequent volcanic eruptions and geothermal activity. Geothermal energy (from hot springs, geysers, etc.) is a major source of heating and electricity in Iceland (Statement 1 is correct). Volcanic eruptions can lead to the creation of new landforms, including islands (like Surtsey) and lava fields (Statement 2 is correct). The dramatic volcanic and glacial landscapes resulting from this tectonic activity, such as geysers, hot springs, volcanoes, and unique rock formations, are major attractions for tourists worldwide (Statement 3 is correct).

Iceland is often referred to as the “Land of Fire and Ice” due to the coexistence of glaciers and volcanoes, both products of its geological setting. The abundance of geothermal energy makes Iceland a leader in renewable energy use. The continuous geological processes shape its unique and appealing landscape for tourism.

48. Which one of the following is not a minor plate ?

Which one of the following is not a minor plate ?

Cocos Plate

Nazca Plate

Caroline Plate

Antarctic Plate

This question was previously asked in

UPSC NDA-1 – 2021

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The correct answer is D) Antarctic Plate.

The Earth’s lithosphere is divided into several large and small tectonic plates. Major plates are generally considered to be the Pacific Plate, North American Plate, Eurasian Plate, Indo-Australian Plate, African Plate, South American Plate, and Antarctic Plate. Minor plates are smaller and often located in complex zones between major plates. The Cocos Plate, Nazca Plate, and Caroline Plate are all classified as minor or intermediate-sized tectonic plates. The Antarctic Plate is one of the seven principal major tectonic plates.

Minor plates include the Arabian Plate, Caribbean Plate, Scotia Plate, Philippine Sea Plate, Fiji Plate, and many others. The classification into “major” and “minor” can sometimes vary slightly depending on the source, but the Antarctic Plate is universally recognized as a major plate due to its large size and significant tectonic boundaries.

49. Which one of the following is an example of Salt-Crystal growth ?

Which one of the following is an example of Salt-Crystal growth ?

Chemical weathering

Physical weathering

Biological weathering

Bio-chemical weathering

This question was previously asked in

UPSC NDA-1 – 2019

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Salt-crystal growth is a form of mechanical weathering (also known as physical weathering) where salts crystallize within the pores and cracks of rocks.

– Salt crystallization occurs when saline water evaporates, leaving salt crystals behind.
– As these crystals grow, they exert pressure on the surrounding rock, causing it to disintegrate.
– This process is particularly effective in arid and semi-arid regions where evaporation rates are high, and in coastal areas exposed to salt spray.

Physical weathering breaks down rocks into smaller pieces without changing their chemical composition. Other examples of physical weathering include frost wedging, thermal expansion and contraction, exfoliation, and abrasion. Chemical weathering involves chemical changes in the rock composition (e.g., dissolution, oxidation, hydrolysis). Biological weathering involves the action of living organisms. Bio-chemical weathering is a combination of biological and chemical processes.

50. Which of the following statements about Ring of Fire is/are correct?

Which of the following statements about Ring of Fire is/are correct?

1. It is a zone of convergence plate boundaries
2. It is an active seismic and volcanic zone
3. It is associated with deep trench

Select the correct answer using the code given below :

1 and 2 only

2 and 3 only

1 only

1, 2 and 3

This question was previously asked in

UPSC NDA-1 – 2018

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The Ring of Fire is a region around the rim of the Pacific Ocean characterized by frequent earthquakes and volcanic activity.
1. It is a zone of convergence plate boundaries: Correct. The Ring of Fire largely follows the boundaries of several tectonic plates, where many convergent plate boundaries exist, leading to subduction.
2. It is an active seismic and volcanic zone: Correct. The high incidence of earthquakes and volcanoes gives the region its name.
3. It is associated with deep trench: Correct. Deep oceanic trenches (like the Mariana Trench, Peru-Chile Trench, etc.) are characteristic features of convergent plate boundaries where subduction occurs, and many of the world’s deepest trenches are located within or along the Ring of Fire.
All three statements accurately describe characteristics of the Ring of Fire.

The Ring of Fire is a direct consequence of plate tectonics, particularly the subduction of oceanic plates beneath continental or other oceanic plates.

Approximately 90% of the world’s earthquakes and 80% of the world’s largest earthquakes occur along the Ring of Fire. It contains 452 volcanoes, more than 75% of the world’s active and dormant volcanoes.