Chapter 2: Geomorphic Processes (Agents of Gradation) (Set-4)
In geomorphic analysis, the balance between weathering rate and removal of weathered material determines landscape form. What happens when the rate of weathering exceeds the rate of erosion over a long period?
A Formation of steep relief
B Accumulation of thick regolith
C Rapid valley deepening
D Development of sharp peaks
When weathering is faster than erosion, broken material accumulates on the surface as regolith. This leads to deep soil profiles and subdued relief, commonly observed in humid tropical regions.
Why is spheroidal weathering more common in basaltic and granitic rocks compared to sedimentary rocks?
A Higher porosity
B Presence of joints and fractures
C Uniform bedding planes
D Low mineral content
Spheroidal weathering occurs when chemical weathering attacks rock edges and corners along joints, rounding blocks. Igneous rocks commonly possess jointed structures favoring this process.
Which geomorphic condition most strongly favors the initiation of debris flows rather than landslides?
A Dry, loose soil
B Saturated slope material with mixed debris
C Hard bedrock slopes
D Gentle slopes with vegetation
Debris flows occur when water-saturated mixtures of soil, rock fragments, and organic matter move downslope rapidly, commonly after intense rainfall in steep terrain.
Why does mass wasting occur even in the absence of external triggering factors such as earthquakes or heavy rainfall?
A Continuous tectonic uplift
B Persistent action of gravity
C Chemical weathering
D Wind erosion
Gravity constantly acts on slope materials. Over time, weathering weakens rock strength, allowing downslope movement even without sudden triggering events.
In river geomorphology, why does sediment size generally decrease from the upper course to the lower course?
A Increase in erosion power downstream
B Selective deposition and abrasion
C Chemical dissolution of minerals
D Reduced transportation capacity
Coarser sediments are deposited earlier due to higher weight, while remaining particles undergo abrasion during transport, becoming finer toward the river’s lower course.
Which factor best explains why waterfalls migrate upstream over geological time?
A Lateral erosion
B Headward erosion at the plunge pool
C Increased sediment load
D Delta formation
Erosion at the base of waterfalls undercuts resistant rock layers, causing collapse and gradual upstream retreat, a process known as headward erosion.
Why do rivers flowing over alternating hard and soft rock layers develop rapids and waterfalls?
A Uniform erosion
B Differential erosion
C Increased discharge
D Meander formation
Softer rocks erode faster than harder layers, creating uneven channel gradients that result in rapids and waterfalls along the river course.
Which wind-related condition most strongly controls the height and migration rate of sand dunes?
A Soil moisture
B Wind velocity
C Rock type
D Groundwater depth
Stronger winds transport more sand and move dunes faster, while wind speed also influences dune height by determining sediment carrying capacity.
Why are transverse dunes commonly found in deserts with abundant sand supply?
A Multidirectional winds
B Strong vegetation cover
C Limited sand availability
D Uniform wind direction and ample sand
Transverse dunes form perpendicular to prevailing winds when sand supply is abundant, allowing continuous ridge development across wind direction.
Which geomorphic process best explains the polishing of bedrock beneath glaciers?
A Chemical corrosion
B Abrasion by embedded debris
C Wind erosion
D Freeze–thaw action
Rock fragments frozen into the glacier base grind against bedrock under immense pressure, smoothing and polishing rock surfaces through abrasion.
Why do cirques represent the initial stage of valley glacier development?
A They form due to deposition
B They are created by river erosion
C They originate at glacier accumulation zones
D They indicate glacier retreat
Cirques develop where snow accumulates and compresses into ice, initiating glacial erosion and marking the birthplace of valley glaciers.
Which marine process is most responsible for the transportation of sediments parallel to the coastline?
A Hydraulic action
B Longshore drift
C Tidal currents
D Marine deposition
Longshore drift results from waves striking the coast at an angle, moving sediments along the shoreline through swash and backwash actions.
Why do barrier beaches form parallel to coastlines rather than perpendicular?
A Strong tidal currents
B Wave refraction
C Dominance of longshore drift
D Coral growth
Continuous sediment transport parallel to the coast by longshore drift accumulates sand into elongated barriers running alongside shorelines.
Which factor most strongly controls the size and shape of sea caves along rocky coasts?
A Rock color
B Structural weaknesses in rocks
C Distance from equator
D Tidal range alone
Joints, faults, and bedding planes allow waves to exploit weak zones, enlarging them into caves through hydraulic action and abrasion.
Why are karst landscapes often associated with sinkhole hazards in populated regions?
A High seismic activity
B Sudden collapse of underground cavities
C Wind erosion
D Volcanic processes
Dissolution enlarges underground voids in limestone. When roofs become unstable, sudden collapse creates sinkholes, posing risks to infrastructure.
Which process explains the enlargement of limestone joints into extensive cave systems?
A Mechanical erosion
B Solution by carbonic acid
C Wind abrasion
D Glacial plucking
Rainwater mixed with carbon dioxide forms carbonic acid, dissolving calcium carbonate along joints and gradually expanding them into caves.
Why does groundwater erosion operate at a much slower rate compared to surface running water?
A Higher viscosity
B Limited oxygen supply
C Lower velocity and confined flow
D Absence of sediments
Groundwater moves slowly through pores and fractures, limiting its mechanical erosive capacity, though chemical dissolution remains effective over long periods.
Which geomorphic agent shows the greatest seasonal variability in erosional effectiveness?
A Wind
B Groundwater
C Glaciers
D Sea waves
Wind strength and direction vary seasonally, directly influencing erosion and deposition rates, especially in arid and semi-arid environments.
Why do floodplains represent zones of both high fertility and high flood risk?
A Steep slopes
B Frequent sediment deposition
C Low rainfall
D High elevation
Floodplains receive nutrient-rich sediments during floods, enhancing fertility, but their low-lying position makes them prone to recurrent flooding.
Which geomorphic feature best indicates repeated episodes of river rejuvenation?
A Meanders
B Ox-bow lakes
C River terraces
D Delta plains
Multiple terraces at different elevations record successive phases of downcutting and stabilization, indicating repeated rejuvenation events.
Why is glacial deposition often poorly sorted compared to fluvial deposition?
A Uniform sediment size
B Selective transport
C Ice transports all particle sizes together
D Chemical precipitation
Glaciers carry fine clay to large boulders simultaneously, depositing unsorted material called till, unlike rivers that sort sediments by size.
Which factor most directly limits the inland extent of marine erosion?
A Wind direction
B Tidal range
C Energy dissipation inland
D Coral reef growth
Wave energy decreases rapidly away from the shoreline, restricting erosional impact to coastal zones and limiting inland penetration.
Why are desert pavements considered indicators of prolonged wind erosion rather than short-term events?
A Presence of vegetation
B Thick soil cover
C Gradual removal of fine particles
D Rapid deposition
Desert pavements form slowly as wind selectively removes fine sediments over long periods, leaving behind coarse, erosion-resistant surfaces.
Which geomorphic condition most favors the formation of pediplains?
A Humid climate
B Active glaciation
C Arid to semi-arid climate with sheet wash
D Marine environment
Pediplains develop where sheet wash and parallel slope retreat dominate under limited vegetation and episodic rainfall conditions.
Why does chemical weathering often produce rounded landforms rather than angular ones?
A Mechanical breakage
B Uniform mineral dissolution at edges
C Wind erosion
D Glacial abrasion
Chemical reactions attack rock corners and edges more rapidly, gradually smoothing and rounding landforms over time.
Which fluvial process primarily causes undercutting of river banks along meander bends?
A Vertical erosion
B Lateral erosion
C Deposition
D Headward erosion
Faster flow on the outer bend of meanders erodes banks laterally, undercutting them and enhancing channel migration.
Why are glaciers capable of transporting extremely large boulders over long distances?
A High flow velocity
B Buoyancy in water
C Ice strength and thickness
D Chemical dissolution
Thick ice can support and carry massive rock fragments embedded within or on its surface, enabling long-distance transport.
Which coastal depositional landform may eventually enclose a lagoon behind it?
A Stack
B Spit
C Cliff
D Wave-cut platform
As spits extend across bays due to longshore drift, they may block off water bodies, forming lagoons behind them.
Why is karst topography rarely developed in regions with impervious rock layers over limestone?
A Excessive rainfall
B Limited groundwater circulation
C Strong wind erosion
D Tectonic uplift
Impervious layers restrict water infiltration into limestone, reducing chemical dissolution necessary for karst feature development.
Which geomorphic agent is most responsible for creating extensive plains of internal drainage?
A Rivers
B Wind
C Glaciers
D Sea waves
In arid regions, wind redistributes sediments within closed basins, contributing to broad plains with internal drainage systems.
Why does mass wasting intensity often increase immediately after earthquakes in mountainous regions?
A Reduced rainfall
B Ground shaking reduces slope stability
C Increased vegetation growth
D River rejuvenation
Earthquake vibrations loosen slope materials and reduce friction, triggering landslides and rockfalls even without rainfall.
Which geomorphic indicator suggests active coastal erosion rather than deposition?
A Wide sandy beach
B Presence of cliffs and notches
C Barrier islands
D Spits
Cliffs and wave-cut notches are formed by strong erosional wave action, indicating dominance of coastal erosion processes.
Why do river deltas often subside over time despite continuous sediment deposition?
A Strong wave erosion
B Compaction of sediments
C Reduced sediment supply
D Wind deflation
Newly deposited delta sediments compact under their own weight, causing gradual subsidence even as new material accumulates.
Which geomorphic process explains the formation of entrenched meanders?
A Gradual deposition
B River rejuvenation with vertical erosion
C Wind erosion
D Glacial melting
When base level falls, rivers cut vertically into existing meanders, preserving their winding shape as deeply incised channels.
Why is weathering considered a preparatory process rather than a transporting process?
A It creates new landforms
B It breaks rocks without moving them
C It deposits sediments
D It increases river velocity
Weathering disintegrates and decomposes rocks in situ, making material available for erosion and transport by other agents.
Which factor best explains why glaciers can erode bedrock below sea level?
A Chemical dissolution
B Buoyant ice movement
C High basal pressure
D Wind abrasion
The immense weight of thick ice exerts strong pressure, enabling glaciers to erode bedrock far below sea level.
Why do desert landscapes often show sharp contrast between erosion and deposition zones?
A Uniform rainfall
B Episodic intense rainfall and strong winds
C Dense vegetation
D Continuous river flow
Infrequent but intense rain causes rapid erosion, while strong winds redistribute sediments, creating sharp spatial contrasts.
Which geomorphic feature forms when groundwater dissolves limestone along a vertical shaft?
A Polje
B Doline
C Sinkhole
D Karst tower
Vertical dissolution and collapse create sinkholes, common karst features formed by downward groundwater erosion.
Why does fluvial deposition increase significantly when rivers enter standing bodies of water?
A Increased velocity
B Sudden loss of energy
C Chemical precipitation
D Wind action
When rivers enter lakes or seas, flow velocity drops sharply, causing sediments to settle and form deltas or alluvial deposits.
Which geomorphic agent is least effective in polar desert environments?
A Wind
B Glaciers
C Running water
D Freeze–thaw
Limited liquid water availability restricts river activity in polar deserts, reducing the effectiveness of running water as an agent.
Why are wave-cut platforms considered indicators of former sea levels?
A They form above high tide
B They develop at current shoreline only
C They record past positions of erosion
D They indicate coral growth
Wave-cut platforms form at sea level during cliff erosion and remain as raised features if sea level changes.
Which geomorphic process dominates slope evolution in periglacial regions?
A Chemical weathering
B Solifluction
C Marine erosion
D Wind deposition
In periglacial areas, seasonal thawing of saturated soil over frozen ground causes slow downslope flow called solifluction.
Why does groundwater contamination spread rapidly in karst regions?
A Slow recharge
B Thick soil cover
C Conduit-controlled flow
D Low permeability
Water moves quickly through underground conduits with minimal filtration, allowing pollutants to travel rapidly through karst aquifers.
Which geomorphic process best explains the widening of valleys during mature river stages?
A Vertical erosion
B Lateral erosion
C Headward erosion
D Chemical weathering
Reduced gradient shifts river energy sideways, widening valleys through bank erosion and floodplain development.
Why are glacial till deposits poor for agriculture compared to fluvial alluvium?
A Low mineral content
B Poor sorting and drainage
C Excessive organic matter
D High salinity
Till contains mixed particle sizes with poor structure and drainage, limiting soil fertility compared to well-sorted river deposits.
Which geomorphic factor primarily controls the spacing of meanders along a river course?
A Channel depth
B Discharge and valley slope
C Water temperature
D Sediment color
River discharge and gradient influence flow energy and lateral erosion patterns, determining meander wavelength and spacing.
Why does coastal erosion accelerate during storm events?
A Reduced wave height
B Increased sediment supply
C High-energy waves and storm surges
D Coral reef growth
Storms generate powerful waves and elevated water levels, intensifying erosion of cliffs, beaches, and coastal structures.
Which geomorphic process explains the formation of limestone pavements with clints and grikes?
A Mechanical weathering
B Chemical dissolution along joints
C Wind abrasion
D Glacial scouring
Carbonic acid dissolves limestone along joints, widening them into grikes and leaving blocks called clints.
Why is understanding geomorphic processes essential for sustainable land-use planning?
A It replaces engineering surveys
B It predicts volcanic eruptions
C It helps assess erosion and hazard risks
D It focuses only on climate change
Knowledge of landform–process relationships aids in evaluating landslide, flood, and erosion risks, supporting safer development decisions.
How does geomorphology contribute to long-term environmental management strategies?
A By controlling weather systems
B By explaining landscape evolution and stability
C By eliminating natural hazards
D By stopping erosion completely
Understanding how landscapes form and change helps manage resources, mitigate hazards, and plan sustainable human activities.