Chapter 2: Geomorphic Processes (Agents of Gradation) (Set-3)
In geomorphology, the concept of weathering front is often used to understand subsurface rock alteration. What does the term weathering front specifically refer to in the context of long-term landscape evolution?
A Boundary between soil and vegetation
B Upper limit of erosion
C Zone between weathered and unweathered rock
D Surface exposed to maximum rainfall
The weathering front represents the transition zone where surface weathering processes penetrate downward, separating altered material above from fresh, unaltered bedrock below, helping explain soil depth and landscape development.
Why is exfoliation weathering particularly associated with massive igneous rocks such as granite in arid and semi-arid regions?
A High rainfall intensity
B Chemical instability of granite
C Temperature-induced expansion and contraction
D Presence of organic acids
In arid regions, large daily temperature variations cause outer rock layers to expand and contract repeatedly, leading to peeling of concentric sheets, a process known as exfoliation common in massive igneous rocks.
Which geomorphic principle explains why slopes composed of unconsolidated material tend to evolve differently from slopes made of hard, resistant bedrock?
A Principle of base level
B Principle of uniformitarianism
C Principle of differential erosion
D Principle of isostasy
Differential erosion explains how variations in rock strength and structure cause uneven erosion rates, resulting in contrasting slope forms and relief even under similar climatic conditions.
The role of vegetation in slope stability is complex and varies with environmental conditions. Under which circumstance can vegetation actually increase the likelihood of mass wasting?
A Deep root systems binding soil
B Reduced surface runoff
C Increased weight due to water retention
D Prevention of weathering
Vegetation can absorb and retain large amounts of water during heavy rainfall, increasing slope load and reducing stability, thereby sometimes triggering landslides despite its stabilizing role.
In fluvial geomorphology, knickpoints are important indicators of landscape change. What does the presence of a knickpoint in a river profile generally signify?
A Zone of deposition
B Sudden change in gradient
C Stable equilibrium
D Floodplain formation
Knickpoints represent abrupt breaks in river slope caused by tectonic uplift, base-level change, or lithological variation, and they migrate upstream through headward erosion.
Why is headward erosion considered a crucial process in the extension of river valleys and drainage basins?
A It deepens river channels vertically
B It increases sediment deposition
C It lengthens river courses upstream
D It stabilizes valley sides
Headward erosion occurs at the source of a river, allowing valleys to extend backward into uplands, sometimes leading to river capture and reorganization of drainage systems.
Which condition most strongly promotes river rejuvenation and renewed vertical erosion after a period of stability?
A Increase in sediment load
B Rise in base level
C Fall in base level
D Decrease in rainfall
A fall in base level, such as sea-level drop or land uplift, increases river gradient, restoring erosional energy and causing renewed downcutting known as rejuvenation.
Why do braided rivers commonly occur in proglacial and semi-arid environments rather than humid tropical regions?
A Presence of dense vegetation
B Low sediment supply
C Highly variable discharge and heavy sediment load
D Strong tidal influence
Braided rivers form where discharge fluctuates widely and sediment supply is excessive, conditions typical of glacier-fed rivers and semi-arid regions with episodic rainfall.
Which aeolian landform provides strong evidence of wind direction stability over long periods?
A Barchan dunes
B Star dunes
C Loess plains
D Deflation hollows
Barchan dunes have crescent shapes with horns pointing downwind, forming only under consistent wind directions and limited sand supply, indicating long-term wind stability.
Why are star dunes considered indicators of complex wind regimes in desert environments?
A They form under low wind velocity
B They grow only near coasts
C They develop under multidirectional winds
D They indicate high rainfall
Star dunes form where wind directions vary seasonally or daily, causing sand to accumulate vertically rather than migrate horizontally, reflecting complex wind patterns.
In glacial geomorphology, what does the presence of roche moutonnée indicate about past ice movement?
A Deposition of sediments only
B Direction and intensity of glacial flow
C Absence of basal sliding
D Volcanic influence
Roche moutonnée features show smooth stoss sides and steep lee sides, revealing both direction of ice movement and erosional processes like abrasion and plucking.
Why are hanging valleys commonly associated with waterfalls in glaciated mountain regions?
A Increased rainfall
B Faster erosion by tributary glaciers
C Unequal glacial erosion depth
D Tectonic uplift
Main glaciers erode valleys more deeply than smaller tributary glaciers, leaving tributary valleys perched above, from which waterfalls often descend.
Which process explains the formation of fjords along high-latitude coastlines?
A Marine deposition
B Subaerial weathering
C Glacial erosion followed by sea-level rise
D Wind abrasion
Fjords are deeply eroded U-shaped glacial valleys later submerged by rising sea levels after glacier retreat, creating narrow, steep-sided inlets.
Why does marine erosion dominate along discordant coastlines compared to concordant coastlines?
A Uniform rock resistance
B Alternating hard and soft rock bands
C Absence of tides
D Low wave energy
Discordant coastlines have rock layers arranged perpendicular to shore, allowing waves to exploit weaker rocks, increasing erosion and creating irregular coastal features.
Which marine process primarily contributes to the sorting of sediments along beaches?
A Hydraulic action
B Wave swash and backwash
C Tidal range variation
D Coral growth
Swash carries sediments up the beach while backwash returns finer material, sorting particles by size and density and creating characteristic beach profiles.
Why do karst regions frequently exhibit underground drainage networks instead of surface river systems?
A Low relief
B Impermeable soil cover
C High rock solubility and jointing
D Strong tectonic activity
Soluble limestone with extensive joints allows water to percolate rapidly underground, forming caves and subterranean channels rather than surface streams.
Which geomorphic feature best indicates an advanced stage of karst development?
A Lapies
B Dolines
C Poljes
D Limestone pavements
Poljes are large, flat-floored depressions formed by extensive dissolution and structural control, representing mature stages of karst landscape evolution.
Why is groundwater considered a powerful geomorphic agent despite its slow movement?
A It transports coarse sediments
B It causes frequent floods
C It operates continuously through chemical action
D It reshapes coastlines
Groundwater dissolves and transports minerals in solution over long periods, gradually modifying rock structures and creating significant landforms like caves.
Which factor most directly controls the depth to which weathering processes can penetrate the Earth’s crust?
A Latitude
B Vegetation cover
C Rock permeability
D Ocean currents
Permeable rocks allow water and gases to penetrate deeper, extending weathering processes below the surface and increasing soil and regolith thickness.
Why are badlands often described as geomorphologically young landscapes?
A They lack vegetation
B They show rapid erosion and little soil development
C They form only in deserts
D They result from glaciation
Intense erosion on soft rocks prevents stable soil and vegetation from forming, keeping badlands in an actively evolving, youthful geomorphic stage.
Which mass wasting process is most closely associated with saturated clay-rich soils on gentle slopes?
A Rockfall
B Earthflow
C Debris avalanche
D Slump
Earthflows involve slow to moderate movement of water-saturated, fine-grained materials, especially clays, commonly occurring on gentle slopes after heavy rainfall.
Why does lateral erosion become dominant during the mature stage of a river’s life cycle?
A Increase in gradient
B Decrease in sediment load
C Reduced vertical erosion
D Increased tectonic uplift
As rivers approach base level, vertical erosion decreases and energy is redirected sideways, widening valleys and developing floodplains and meanders.
Which aeolian deposit contributes significantly to agricultural productivity in parts of China and Europe?
A Sand dunes
B Ventifacts
C Loess
D Desert pavement
Loess consists of wind-blown silt that forms fertile, well-drained soils, supporting intensive agriculture in several temperate regions.
Why are glacial erratics important indicators in reconstructing past glacial extent?
A They form only in mountains
B They are composed of local rock
C They differ from surrounding bedrock
D They indicate volcanic activity
Erratics are transported far from their source by glaciers, and their contrasting lithology helps trace ice movement and former glacier limits.
Which coastal landform develops due to the erosion of weaker rock layers beneath stronger layers?
A Stack
B Arch
C Cave
D Wave-cut notch
Persistent wave action erodes softer rock at the cliff base, forming a notch that eventually leads to cliff collapse and retreat.
Why does chemical weathering intensity generally increase toward the equator?
A Higher altitude
B Greater solar radiation and rainfall
C Stronger winds
D Frequent glaciation
Increased heat accelerates chemical reactions while abundant rainfall supplies moisture, together enhancing chemical weathering in equatorial regions.
Which geomorphic process explains the formation of river terraces?
A Continuous deposition
B Alternating erosion and deposition due to rejuvenation
C Wind erosion
D Glacial melting
River terraces form when rivers cut down into former floodplains following rejuvenation, leaving step-like remnants of earlier valley floors.
Why do glaciers erode more effectively than rivers in high mountain environments?
A Higher velocity
B Greater erosive tools
C Immense weight and pressure
D Chemical dissolution
The enormous mass of ice exerts high pressure on bedrock, intensifying abrasion and plucking, making glaciers powerful erosional agents.
Which factor limits the effectiveness of wind as a geomorphic agent in humid regions?
A High temperature
B Dense vegetation cover
C Flat relief
D Sandy soil
Vegetation stabilizes soil and traps sediments, reducing wind speed near the surface and limiting erosion and transport by wind.
Why are karst aquifers particularly vulnerable to pollution?
A Slow groundwater movement
B High filtration capacity
C Direct recharge through sinkholes
D Low water usage
Water enters karst systems rapidly through sinkholes with minimal filtration, allowing pollutants to spread quickly through groundwater networks.
Which geomorphic agent is primarily responsible for shaping continental interiors over millions of years?
A Sea waves
B Wind
C Running water
D Icebergs
Rivers operate continuously across continents, removing weathered material and transporting sediments to oceans, making them dominant long-term agents.
Why does mass wasting often increase after deforestation in hilly regions?
A Reduced rainfall
B Loss of root binding and increased runoff
C Decreased slope angle
D Increased rock strength
Tree roots stabilize soil and absorb water. Deforestation weakens slope cohesion and increases surface runoff, triggering landslides and soil movement.
Which glacial landform marks the former maximum extent of a glacier?
A Ground moraine
B Terminal moraine
C Esker
D Kame
Terminal moraines form at the furthest advance of glaciers, recording their maximum reach during glacial periods.
Why do coastal depositional features commonly shift position over time?
A Constant tectonic uplift
B Changing wave and current patterns
C Uniform sediment supply
D Fixed wind direction
Variations in wave energy, currents, and sediment supply alter erosion and deposition patterns, causing coastal landforms to migrate.
Which geomorphic process best explains the smoothening of desert rock surfaces?
A Chemical corrosion
B Wind abrasion
C Glacial polishing
D Marine action
Wind-driven sand particles continuously strike exposed rocks, polishing and smoothing surfaces through abrasion in arid environments.
Why does physical weathering dominate in high-altitude mountain regions?
A High humidity
B Frequent freeze–thaw cycles
C Dense vegetation
D Chemical instability
Repeated freezing and thawing of water in rock cracks causes expansion and contraction, breaking rocks mechanically at high altitudes.
Which fluvial feature indicates a river nearing dynamic equilibrium?
A Waterfall
B Straight channel
C Graded profile
D Gorge
A graded river profile reflects balance between erosion, transportation, and deposition, indicating near-equilibrium conditions.
Why are sand dunes absent in most humid tropical regions despite abundant sand supply?
A Strong winds
B High rainfall and vegetation cover
C Low temperatures
D Tectonic stability
Moisture binds sand grains and dense vegetation anchors sediments, preventing wind from transporting and accumulating sand into dunes.
Which geomorphic process is most responsible for shaping wave-dominated coastlines?
A Longshore drift
B Hydraulic action and abrasion
C Tidal deposition
D Coral accretion
Powerful waves exert pressure and use rock fragments as tools, eroding cliffs and shaping coastlines dominated by wave energy.
Why is slope angle a critical factor in determining the type of mass wasting?
A It controls rainfall
B It determines gravitational force component
C It affects rock color
D It influences temperature
Steeper slopes increase the downslope component of gravity, raising the likelihood and speed of mass movement.
Which landform results from deposition by meltwater streams flowing beneath glaciers?
A Moraine
B Drumlin
C Esker
D Cirque
Eskers are long, sinuous ridges of sand and gravel deposited by subglacial meltwater streams flowing within ice tunnels.
Why does groundwater erosion play a limited role in shaping hard crystalline rocks?
A High rainfall
B Low permeability
C Strong wave action
D Frequent earthquakes
Crystalline rocks lack extensive joints and pores, restricting water movement and limiting chemical dissolution by groundwater.
Which geomorphic feature indicates prolonged wind erosion rather than deposition?
A Loess
B Barchan dune
C Desert pavement
D Sand sheet
Desert pavements form when wind removes fine particles, leaving a surface covered with coarse fragments resistant to further erosion.
Why are glacial landscapes often characterized by poor drainage after ice retreat?
A High rainfall
B Impermeable till deposits
C Steep slopes
D Marine influence
Glacial till is often compact and impermeable, impeding infiltration and creating poorly drained landscapes with lakes and wetlands.
Which factor best explains why karst springs often have highly variable discharge?
A Constant rainfall
B Uniform aquifer structure
C Rapid conduit flow
D Low evaporation
Water moves quickly through underground channels in karst systems, causing spring discharge to respond rapidly to rainfall changes.
Why does river capture significantly alter regional drainage patterns?
A It increases rainfall
B It redirects stream flow between basins
C It reduces erosion
D It stabilizes channels
River capture diverts water from one drainage basin to another through headward erosion, reorganizing regional hydrology.
Which geomorphic agent is least influenced by short-term climatic fluctuations?
A Wind
B Sea waves
C Running water
D Groundwater
Groundwater systems respond slowly to surface climatic changes, making them less sensitive to short-term variations compared to surface agents.
Why do wave-cut platforms widen over time?
A Increased deposition
B Continuous cliff retreat
C Tectonic uplift
D Coral growth
As cliffs erode and retreat landward under wave attack, the eroded surface expands seaward, widening the wave-cut platform.
Which geomorphic process explains the rounding of pebbles in river channels?
A Chemical corrosion
B Attrition and abrasion
C Freeze–thaw action
D Mass wasting
Pebbles collide and scrape against each other and channel beds during transport, becoming rounded through abrasion and attrition.
Why is geomorphology considered essential for understanding natural hazard risks such as landslides and floods?
A It predicts earthquakes
B It explains landform–process relationships
C It replaces engineering studies
D It focuses only on climate
Understanding how landforms evolve under geomorphic processes helps assess slope stability, flood behavior, and erosion patterns, aiding hazard prediction and management.