Weathering & Erosion – NDA Geography PYQs

NDA 2019-II

Q. 1. Monadnock is:

(a) A deep depression formed by glacial action

(b) An isolated resistant hill standing above a peneplain

(c) A landform formed by wave erosion

(d) A deposition feature of rivers

Answer: (b) An isolated resistant hill standing above a peneplain

Explanation: A Monadnock (also called an inselberg in some contexts) is an isolated hill or rocky prominence that stands above a peneplain (a nearly flat erosional plain). It is formed when most of a landmass has been worn down to a flat surface by prolonged erosion, but a patch of more resistant rock survives and protrudes above the surrounding plain. The term comes from Mount Monadnock in New Hampshire, USA. Examples: Uluru (Ayers Rock) in Australia is often cited as a type of monadnock/inselberg. Concept Tested: Monadnock: isolated resistant hill rising above a peneplain; resistant rock survives when surrounding rock is eroded flat

NDA 2018-II

Q. 2. Deep chemical weathering is a characteristic feature of which type of climate?

(a) Polar

(b) Hot desert

(c) Humid tropical

(d) Mediterranean

Answer: (c) Humid tropical

Explanation: Chemical weathering is most intense in humid tropical climates because: 1. High temperature: accelerates chemical reaction rates (roughly double with every 10°C rise). 2. High humidity and rainfall: provides the water needed for hydrolysis, hydration, carbonation, and oxidation reactions. In humid tropical regions, the chemical weathering profile can extend to depths of 30–60 metres or more, producing deep laterite soil. In polar regions, chemical weathering is minimal (too cold). In hot deserts, mechanical weathering dominates (little water for chemical reactions). Mediterranean climates have seasonal weathering. Concept Tested: Deep chemical weathering in humid tropical climate: high temperature + abundant water accelerate chemical reactions

NDA 2016-II

Q. 3. Frost action is an example of:

(a) Chemical weathering

(b) Biological weathering

(c) Deposition

(d) Mechanical weathering

Answer: (d) Mechanical weathering

Explanation: Frost action (freeze-thaw weathering) is a mechanical weathering process. Water seeps into cracks in rocks. When temperatures drop below freezing, the water expands by about 9% as it freezes into ice. This expansion exerts tremendous pressure on the surrounding rock, widening cracks. Repeated freeze-thaw cycles eventually break the rock apart into angular fragments (scree/talus). No chemical change in rock composition occurs: it is purely physical/mechanical. Concept Tested: Frost action (freeze-thaw): mechanical weathering; water freezes and expands in rock cracks, breaking rock apart

NDA 2016-I

Q. 4. Rias are:

(a) Drowned river valleys

(b) Glaciated valleys

(c) River valleys in lower course

(d) Broad valleys between two mountains

Answer: (a) Drowned river valleys

Explanation: Rias (or ria coastlines) are formed when sea level rises and floods the lower portion of river valleys. The result is a wedge-shaped inlet (wide at the sea, narrowing inland): a drowned river valley. Rias are found on coastlines of emergent seas: where the land has subsided or sea level has risen. Examples: the rias of northwestern Spain, the estuaries of southwestern England, and the coast of Brittany (France). Rias differ from Fjords (which are drowned glacial valleys) in that rias have a V-shaped cross-section and are found in warmer climates. Concept Tested: Rias: drowned river valleys; formed when sea level rises and floods river valleys near the coast

★ JOVIK Exam Insight Coastal geomorphology for NDA: distinguish between: Rias: drowned river valleys; V-shaped; warmer climate coasts (Spain, France, England). Fjords: drowned glacial U-shaped valleys; steep sides; cold climate coasts (Norway, New Zealand, Canada, Patagonia). Eskers: glacial deposition ridges (not coastal). Delta: river deposition at sea/lake mouth. Both Rias and Fjords are created by sea level rise (submergent coasts).

NDA 2015-I

Q. 5. Kettle holes are landforms associated with:

(a) Glacial deposition

(b) Glacial erosion

(c) Wind deposition

(d) River erosion

Answer: (a) Glacial deposition

Explanation: Kettle holes (kettles) are depressions or holes in glacial outwash plains formed by glacial deposition processes. They are created when a block of ice becomes buried in glacial sediment (outwash). When the ice melts, it leaves behind a circular depression: which may fill with water to form a kettle lake. Kettle holes are associated with glaciofluvial (meltwater) deposition: a type of glacial deposition. Examples: The lakes of Minnesota (USA) are often kettle lakes. The Brøndby crater in Denmark is a kettle. Concept Tested: Kettle holes: glacial DEPOSITION features; formed by melting buried ice blocks in glacial outwash

NDA 2014-I

Q. 6. Yardang is a landform produced by:

(a) Glacier

(b) Wind

(c) Water

(d) Wave action

Answer: (b) Wind

Explanation: A Yardang is a streamlined rock or sediment mound carved by wind abrasion. Yardangs have a smooth, aerodynamic shape aligned parallel to the dominant wind direction: they are often described as looking like the inverted hull of a boat. They are found in arid and hyper-arid desert environments where wind erosion is intense (e.g., Sahara, Arabian Desert, China’s Tarim Basin). Yardangs are classified as aeolian (wind) erosion landforms. Concept Tested: Yardang: streamlined landform carved by wind abrasion; aeolian erosion feature in desert environments

NDA 2013-I

Q. 7. Which one among the following features is not associated with glacial erosion?

(a) Barchan

(b) Cirque

(c) Hanging valley

(d) Fiord

Answer: (a) Barchan

Explanation: Glacial erosion features include: Cirque (corrie): bowl-shaped depression carved by a glacier at its head; U-shaped valley: carved by a moving glacier (flat-bottomed, steep-sided); Hanging valley: a tributary valley that ends high above the main valley floor; Fiord (Fjord): a drowned glacial U-shaped valley. Barchan is a crescent-shaped sand dune: formed by wind erosion in deserts (aeolian landform), not glacial erosion. Concept Tested: Barchan (aeolian/wind dune) is NOT a glacial erosion feature; Cirque, Hanging valley, Fjord are glacial

NDA 2012-II

Q. 8. Limestone caves are formed due to which type of weathering?

(a) Physical weathering

(b) Biological weathering

(c) Chemical weathering

(d) Thermal weathering

Answer: (c) Chemical weathering

Explanation: Limestone caves are formed by a chemical weathering process called carbonation (or corrosion). When rainwater absorbs CO₂ from the atmosphere, it forms carbonic acid (H₂CO₃). This weak acid reacts with calcium carbonate (CaCO₃) in limestone: CaCO₃ + H₂CO₃ → Ca(HCO₃)₂ (calcium bicarbonate: soluble) The limestone is slowly dissolved and carried away by water, creating underground caves, sinkholes, stalactites, and stalagmites: collectively called karst topography. Concept Tested: Limestone caves: formed by carbonation (chemical weathering); CO₂ + water → carbonic acid dissolves CaCO₃

NDA 2012-I

Q. 9. Which one among the following is NOT an agent of erosion?

(a) Earthquake

(b) Running water

(c) Glacier

(d) Wind

Answer: (a) Earthquake

Explanation: Agents of erosion are external forces that wear away and transport rock material from one place to another. Running water (b): the most powerful erosional agent globally; erodes river valleys, gorges, and plains. Glacier (c): a powerful erosional agent; creates U-shaped valleys, cirques, fjords, and drumlins. Wind (d): an erosional agent in arid regions; creates yardangs, zeugen, inselbergs. Earthquake (a): an INTERNAL/TECTONIC event, not an external erosional agent. Earthquakes cause ground shaking and displacement but are not classified as agents of erosion. Concept Tested: Earthquake is NOT an agent of erosion (it is a tectonic event); Running water, Glaciers, Wind are erosional agents

NDA 2011-I

Q. 10. Which one among the following is not an aeolian landform?

(a) Barchan

(b) Zeugen

(c) Stalactite

(d) Seif

Answer: (c) Stalactite

Explanation: Aeolian landforms are created by wind (from the Greek god Aeolus: god of wind). Barchan (a): a crescent-shaped sand dune formed by wind in deserts. Aeolian ✓. Zeugen (b): a table-like rock landform created by differential wind erosion (softer layer eroded below harder cap). Aeolian ✓. Seif (d): a long longitudinal sand dune parallel to the prevailing wind direction. Aeolian ✓. Stalactite (c): a calcium carbonate deposit hanging from the ceiling of a cave, formed by water (karst/cave process). NOT an aeolian landform ✗. Concept Tested: Stalactite is a karst/cave landform formed by water: not aeolian; Barchan, Zeugen, Seif are wind landforms

NDA 2010-I

Q. 11. Block disintegration is a type of:

(a) Mechanical weathering

(b) Chemical weathering

(c) Biological weathering

(d) None of the above

Answer: (a) Mechanical weathering

Explanation: Block disintegration is a mechanical weathering process in which rocks split into angular blocks along existing joints and fracture planes. It is caused by extreme daily temperature changes: expansion during the day and contraction at night. In hot desert environments, rocks with well-developed joint systems break apart into angular blocks through this repeated thermal stress. No chemical change occurs in block disintegration: it is purely physical. Concept Tested: Block disintegration: mechanical weathering; rocks split along joints due to thermal expansion and contraction

NDA 2009-II

Q. 12. Which of the following is/are example/examples of chemical weathering?

(a) Hydrolysis, Oxidation and Carbonation

(b) Frost action

(c) Hydrolysis only

(d) Oxidation and Carbonation only

Answer: (a) Hydrolysis, Oxidation and Carbonation

Explanation: Chemical weathering involves changes in the chemical composition of rock minerals. Hydrolysis: water chemically combines with minerals, altering them (e.g., feldspar → clay minerals). Oxidation: minerals react with oxygen (e.g., iron minerals rust, forming iron oxides/hydroxides; causes red colouration). Carbonation: CO₂ dissolves in water to form carbonic acid, which dissolves calcium carbonate rocks (limestone, chalk): the basis of karst topography. Frost action (freeze-thaw) is a MECHANICAL weathering process: it physically breaks rocks but does not change their chemistry. Concept Tested: Chemical weathering types: Hydrolysis, Oxidation, Carbonation (chemical change); Frost action is mechanical

★ JOVIK Exam Insight Weathering classification for NDA: Mechanical (Physical): Frost action (freeze-thaw), Exfoliation (thermal), Block disintegration, Pressure release, Granular disintegration. Chemical: Hydrolysis, Oxidation, Carbonation, Hydration, Solution. Biological: Roots breaking rocks, organisms secreting acids. Climate determines which dominates: Cold regions = mechanical (frost action); Hot deserts = mechanical (thermal); Humid tropics = chemical.

NDA 2009-I

Q. 13. Exfoliation as a process of weathering is most prevalent in:

(a) Humid tropical regions

(b) Polar Regions

(c) Temperate regions

(d) Hot deserts

Answer: (d) Hot deserts

Explanation: Exfoliation (also called onion-skin weathering or spheroidal weathering) is a process where concentric shells peel off the surface of rocks, similar to peeling an onion. It is most prevalent in hot desert regions where extreme daily temperature variations cause repeated expansion (during the hot day) and contraction (during the cold night) of the outer rock surface. Over time, these repeated stresses cause the outer layers to detach from the rock mass. In humid tropical regions, chemical weathering dominates. In polar regions, frost action (freeze-thaw) is dominant. Concept Tested: Exfoliation: thermal weathering in hot deserts; repeated heating-cooling causes outer rock shells to peel

NDA 2007-I

Q. 14. Weathering that involves the physical disintegration of rocks without any change in their chemical composition is termed as:

(a) Chemical weathering

(b) Mechanical weathering

(c) Chemical decomposition

(d) Biological weathering

Answer: (b) Mechanical weathering

Explanation: Mechanical weathering (also called physical weathering) is the breakdown of rocks into smaller fragments WITHOUT any change in the mineral composition of the rock. The rock is simply broken into smaller pieces of the same material. Processes include: frost action (freeze-thaw), thermal expansion and contraction (insolation weathering), exfoliation, block disintegration, and pressure release. Chemical weathering involves chemical changes to rock minerals (decomposition). Biological weathering involves the action of living organisms. Concept Tested: Mechanical weathering: physical disintegration of rock; no chemical change in composition

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