Why this chapter matters for UPSC: "Geomorphic Processes" is Chapter 5 of Fundamentals of Physical Geography in the current rationalised NCERT (Reprint 2026-27). It was Chapter 6 before Minerals and Rocks was dropped; this site keeps the old number. The rationalised text shortened the detailed accounts of individual weathering processes and of slow and rapid flow movements; this page covers both, marking what comes from the pre-2022 edition. The chapter's mass-movement section is the basis of five Mains questions on landslides (GS1 2013, 2016, 2021; GS3 2019, 2021).

Contemporary hook: About 0.42 million km², nearly 12.6% of India's land area, is prone to landslides, according to the Geological Survey of India figure quoted by NDMA in its National Landslide Risk Mitigation Programme document (2025). On 30 July 2024 a series of landslides struck Mundakkai, Chooralmala and nearby villages of Wayanad district, Kerala, in the Western Ghats (PIB, 31 July 2024; NDMA case-study compendium).

🧠 First Principles — Read This First

The Earth's surface is uneven because two sets of forces act on it in opposite directions. Endogenic forces come from inside the Earth. Their energy comes from radioactivity, rotational and tidal friction, and heat left over from the Earth's formation. They raise mountains, warp continents and cause earthquakes and volcanoes: they build relief. Exogenic forces work at the surface. Their energy comes ultimately from the Sun, through the atmosphere, and from the slopes created by tectonic uplift. Rain, rivers, ice, wind and waves wear the high places down and fill the low places up. NCERT puts it this way: the earth is "a playfield for two opposing groups of geomorphic processes". As long as both keep working, the surface never becomes flat.

Three terms need separating from the start. Weathering breaks rock down where it lies; almost nothing moves. Mass movement shifts rock and soil downslope under gravity alone; no river, glacier or wind carries the material. Erosion is removal and transport by a moving agent such as running water, a glacier or wind. In short: weathering loosens, gravity drops, agents carry. Deposition happens when an agent slows down and can no longer carry its load.

Weathered rock is also the raw material of soil, so the chapter ends with how soil forms.

UPSC asks about the classification of these processes in Prelims. In Mains it asks about landslides, mainly why they are more frequent in the Himalaya than in the Western Ghats and how to manage the risk.

PART 1 — Quick Reference

Table 1: NCERT key terms

TermNCERT meaning
Geomorphic processesEndogenic and exogenic forces causing physical stresses and chemical actions on earth materials and changing the configuration of the surface
Geomorphic agentA mobile medium (running water, moving ice, wind, waves and currents, groundwater) that removes, transports and deposits earth materials
DegradationWearing down of relief by exogenic forces
AggradationFilling up of basins and depressions
Gradation"The phenomenon of wearing down of relief variations of the surface of the earth through erosion"
DenudationGeneral term for all exogenic processes: weathering, mass wasting or movements, erosion and transportation ("denude" means to strip off or uncover)
WeatheringMechanical disintegration and chemical decomposition of rocks by elements of weather and climate; an in-situ process
EnrichmentWeathering removes some material by leaching, which raises the concentration of valuable ores (iron, manganese, aluminium, copper) that remain
Mass movementsTransfer of rock debris downslope under the direct influence of gravity
ErosionAcquisition and transportation of rock debris by agents
PedogenesisSoil formation

Source: NCERT FoPG (rationalised), Chapter 5, pp. 37–44. Some other textbooks use "gradation" for degradation and aggradation together; NCERT's definition above is the one its exercise tests.

Table 2: Endogenic and exogenic processes

FeatureEndogenicExogenic
EnergyFrom within the Earth: radioactivity, rotational and tidal friction, primordial heatFrom the atmosphere, set by the Sun's energy, plus gradients created by tectonic factors
ProcessesDiastrophism and volcanismWeathering, mass wasting, erosion, deposition
Main effectLand buildingLand wearing
PaceMostly slow (orogeny, epeirogeny), but earthquakes and eruptions are suddenMostly small and slow, with effects building up through "continued fatigue"

Table 3: Diastrophism (NCERT)

ProcessWhat it does
OrogenyMountain building through severe folding of long, narrow belts of the crust
EpeirogenyUplift or warping of large parts of the crust; "continental building", with simple deformation
EarthquakesLocal, relatively minor movements
Plate tectonicsHorizontal movements of crustal plates

All four can fault and fracture the crust and cause pressure, volume and temperature (PVT) changes that metamorphose rocks.

Table 4: Weathering processes

GroupProcessesEdition
ChemicalSolution, carbonation, hydration, oxidation and reductionNamed in the current edition; described in detail in the pre-2022 edition
Physical (mechanical)Driven by gravitational forces (overburden pressure, load, shearing stress); expansion forces (temperature change, crystal growth, animal activity); water pressure from wetting and drying. Most physical weathering comes from thermal expansion and pressure releaseCurrent edition. Sub-processes (unloading, temperature change, frost, salt) are from the pre-2022 edition
BiologicalBurrowing and wedging by earthworms, termites and rodents; human disturbance of vegetation and soil; humic, carbonic and other acids from decaying matter; pressure of plant rootsCurrent edition

Table 5: Mass movements

FormTypeSpeed and moistureEdition
HeaveHeaving up of soil by frost growth and other causes—Current
Flow (slow)Creep (soil, talus, rock, rock-glacier creep); solifluctionExtremely slow; solifluction involves water-saturated soilPre-2022
Flow (rapid)Earthflow; mudflow; debris avalancheRapid; mostly humid regions; saturated material. Debris avalanche can be much faster than mudflowPre-2022 (debris avalanche as a rapid flow is in the current exercises)
Slide (landslides)Slump, debris slide, debris fall, rockslide, rock fallRelatively rapid and perceptible; material relatively dryCurrent

Table 6: Agents of erosion (NCERT)

AgentState of matterControlled by
WindGasClimate
Running waterLiquidClimate
GlaciersSolidClimate
Waves—Location at the land–sea interface (coast)
Groundwater—Lithology (karst forms only where rocks are permeable and soluble and water is available)

Table 7: Soil-forming factors (NCERT)

FactorActive or passiveMain role
Parent materialPassiveTexture, structure, mineral and chemical make-up of the weathered debris or transported deposit
TopographyPassiveExposure to sunlight and drainage; thin soils on steep slopes, thick soils on flat uplands
ClimateActiveMoisture (eluviation, illuviation, desilication, hardpans, kankar) and temperature
Biological activityActiveHumus, nitrogen fixation, mixing by animals
TimePassiveMaturity and profile development

PART 2 — Concepts & Narrative

Processes and agents

NCERT separates a process (a force applied on earth materials) from an agent (a mobile medium that removes, transports and deposits them). For exogenic processes, NCERT says the two can be treated as one and the same unless stated separately.

Gravity matters in two ways. It is the directional force that drives every downslope movement, and it also creates stresses in earth materials. NCERT notes that without gravity and gradients there would be no mobility and so no erosion, transportation or deposition. All movements, inside the Earth or on its surface, happen down gradients: from higher to lower levels and from high to low pressure.

Endogenic processes

The energy behind endogenic processes comes mostly from radioactivity, rotational and tidal friction, and primordial heat from the Earth's origin. This energy, through geothermal gradients and heat flow, causes diastrophism and volcanism (Table 3). Because heat flow, crustal thickness and crustal strength vary from place to place, endogenic forces act unevenly, and the original crustal surface is uneven.

Volcanism covers the movement of magma onto or towards the surface and the intrusive and extrusive forms it creates; NCERT covers these in Chapter 3, "Interior of the Earth".

Exogenic processes

Exogenic processes take their energy from the atmosphere, driven by the Sun, and from slopes created by tectonics. Gravity acts on every sloping surface. Force per unit area is stress; shear stresses along the faces of materials break rocks and cause slippage. Materials also suffer molecular stresses from temperature change, crystallisation and melting, while chemical processes loosen the bonds between grains. NCERT's conclusion: the basic cause of weathering, mass movement and erosion is the development of stresses in earth materials.

Exogenic processes vary between climatic regions, mainly with temperature and precipitation. Within a region they also vary with altitude, aspect (north- and south-facing slopes receive different insolation), wind, rainfall intensity, daily temperature range and frost frequency. Where climate is the same, rock type and structure decide the rate: folds, faults, joints, bedding planes, hardness, chemical susceptibility and permeability. A rock may resist one process and give way to another, and the same rock may behave differently in different climates. The result is differential rates of denudation and therefore differences in topography.

Weathering

NCERT defines weathering as "mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate". Since very little or no motion takes place, it is in situ. Climate controls both the type of weathering and the depth of the weathering mantle. The three groups rarely act alone, but one usually dominates.

Chemical weathering (pre-2022 detail):

  • Solution: solids dissolve in water or weak acids. Nitrates, sulphates, potassium and common salt are affected; such minerals are leached away in rainy climates and accumulate in dry ones. Calcium carbonate in limestone dissolves in water containing carbonic acid.
  • Carbonation: carbon dioxide from the air and soil air dissolves in water to form weak carbonic acid, which breaks down feldspars and carbonate minerals. Calcium and magnesium carbonates are removed in solution without residue, which forms caves.
  • Hydration: chemical addition of water. Minerals take up water and expand; calcium sulphate turns to gypsum. The process is reversible, and repeated swelling and shrinking (as in clays) causes fatigue and cracking.
  • Oxidation: combination with oxygen to form oxides or hydroxides, where there is ready access to air and oxygenated water. Iron, manganese and sulphur minerals are most affected.
  • Reduction: where oxygen is absent (below the water table, in stagnant water and waterlogged ground), oxidised minerals are reduced; the red colour of iron turns greenish or bluish grey.

Hydration, carbonation and oxidation usually act together and speed each other up.

Physical weathering (pre-2022 detail):

  • Unloading and expansion: erosion removes overlying rock, the pressure drops, and the upper layers expand and fracture roughly parallel to the surface. On curved surfaces this produces massive exfoliation sheets and large, smooth exfoliation domes.
  • Temperature change and expansion: minerals expand and contract with daily heating and cooling and push against each other. This is most effective in dry climates and at high elevations, where daily temperature changes are large. In granite it produces smooth, rounded boulders called tors.
  • Freezing, thawing and frost wedging: ice grows in pores and cracks during repeated freezing and melting, widening them until the rock breaks. Most effective at high elevations in middle latitudes; rapid freezing is most damaging. Water expands by about 9% when it freezes (NOAA JetStream).
  • Salt weathering: salts expand through heat, hydration and crystallisation. Desert surface temperatures of 30–50 °C favour it. Salt crystallisation is the most effective form; grains fall off one by one (granular disintegration). Chalk breaks down most readily, followed by limestone, sandstone, shale, gneiss and granite.

Biological weathering is covered in Table 4. NCERT's point about human beings is that disturbing vegetation, ploughing and cultivating expose new surfaces to air and water.

Key Term

Exfoliation is a result, not a process. NCERT says so explicitly. Exfoliation is the flaking off of curved sheets or shells from rock, leaving smooth, rounded surfaces. It is produced by several processes already described: unloading, thermal expansion and contraction, and salt weathering. NCERT then pairs the landforms with their causes: exfoliation domes result from unloading; tors result from thermal expansion. A question that lists exfoliation as a weathering process, or links domes to temperature change, is testing this distinction.

Significance of weathering

NCERT gives four reasons why weathering matters:

  1. It breaks rocks into fragments and so prepares the way for regolith and soil, and for erosion and mass movement. Erosion cannot be significant if rocks are not weathered.
  2. Biomes and biodiversity depend on forests, and forests depend on the depth of the weathering mantle. This is NCERT's answer to "It is weathering that is responsible for bio-diversity on the earth. How?"
  3. It concentrates valuable ores of iron, manganese, aluminium and copper by enrichment: leaching removes other material and raises the concentration of what remains, to a level that may be economic to mine.
  4. It is an important process in soil formation.
Explainer

Are physical and chemical weathering independent? No, and NCERT asks this as a long-answer question. Physical weathering cracks rock and increases the surface area exposed to water and air, which speeds chemical attack. Chemical processes, in turn, weaken rock physically: hydration makes minerals swell, and NCERT notes that volume changes from hydration help physical weathering through exfoliation and granular disintegration. Salt weathering combines both, since salts expand through hydration and crystallisation. Climate decides which group dominates: chemical activity rises with temperature and moisture, while frost and salt weathering are strongest in cold and dry places.

Mass movements

Mass movements transfer rock debris downslope under the direct influence of gravity. Air, water or ice do not carry the debris, though the debris may carry them. Movements range from slow to rapid and shallow to deep, and include creep, flow, slide and fall.

NCERT draws two conclusions that are often tested:

  • Weathering is not a prerequisite for mass movement, because gravity acts on bedrock too. Weathering helps, and mass movements are much more active on weathered slopes.
  • Mass movements are not erosion. No geomorphic agent takes part, even though material shifts from one place to another.

Material on a slope yields only when the disturbing force exceeds its shearing resistance. Weak unconsolidated materials, thinly bedded rocks, faults, steeply dipping beds, vertical cliffs or steep slopes, heavy or torrential rain and scarce vegetation favour mass movement. NCERT lists nine activating causes:

  1. Removal of support from below, naturally or artificially.
  2. Increase in the gradient and height of slopes.
  3. Overloading by adding material, naturally or by artificial filling.
  4. Overloading by heavy rainfall, saturation and lubrication.
  5. Removal of material or load from the original slope surface.
  6. Earthquakes, explosions or machinery.
  7. Excessive natural seepage.
  8. Heavy drawdown of water from lakes, reservoirs and rivers, causing slow outflow of water from under slopes or banks.
  9. Indiscriminate removal of natural vegetation.

Slow movements (pre-2022 detail). Creep occurs on moderately steep, soil-covered slopes and is imperceptible except over long observation; fence posts and telephone poles leaning downslope are the sign. Solifluction is the slow downslope flow of soil or fine debris saturated with water, common where the surface of deeply frozen ground melts or rain continues for long periods, and the lower layers are impervious.

Rapid flow movements (pre-2022 detail). These are mostly in humid regions. Earthflow is the movement of water-saturated clayey or silty material down low-angle terraces or hillsides. Mudflow occurs where thick weathered material without vegetation is saturated by heavy rain and flows down definite channels like a stream of mud; it is frequent on the slopes of erupting or recently erupted volcanoes, where ash turns to mud. Debris avalanche occurs in narrow tracks on steep slopes in humid regions and can be much faster than a mudflow. NCERT's exercise classes it as a rapid flow mass movement, not a landslide.

Landslides (current edition). These are relatively rapid, perceptible movements of relatively dry material. The size and shape of the mass depend on the discontinuities in the rock, the degree of weathering and the steepness of slope. NCERT's types:

  • Slump: one or more units of debris slip with a backward rotation relative to the slope.
  • Debris slide: rapid rolling or sliding of earth debris without backward rotation.
  • Debris fall: nearly free fall of earth debris from a vertical or overhanging face.
  • Rockslide: individual rock masses slide down bedding, joint or fault surfaces; very fast and destructive on steep slopes; planar failure along steeply dipping discontinuities.
  • Rock fall: free fall of rock blocks from any steep slope, keeping away from the slope. It affects only the superficial layers of the rock face, unlike a rockslide, which affects material to a substantial depth.
UPSC Connect

Himalaya vs Western Ghats and Nilgiris (NCERT's box). Debris avalanches and landslides are very frequent in the Himalaya because the range is tectonically active, made mostly of sedimentary rocks and unconsolidated or semi-consolidated deposits, and very steep. The Nilgiris and the Western Ghats are tectonically relatively stable and made mostly of very hard rocks, yet debris avalanches and landslides still occur there, though less often. NCERT's reasons: many slopes are steeper, with almost vertical cliffs and escarpments; mechanical weathering from temperature changes is pronounced; and heavy rain falls over short periods, causing frequent rock falls along with landslides and debris avalanches. This box is the core of three Mains questions: gs1-pyq-2013-22a, gs1-pyq-2016-14 and gs1-pyq-2021-06.

Erosion and deposition

Erosion is the acquisition and transportation of rock debris by running water, groundwater, glaciers, wind and waves. Abrasion by the debris these agents carry adds to it. Through erosion, relief degrades. Weathering aids erosion but is not a pre-condition for it. Weathering, mass wasting and erosion are all degradational processes, and erosion is largely responsible for the continuous change of the surface.

Erosion and transport are controlled by kinetic energy. The pre-2022 edition defined erosion as the "application of the kinetic energy associated with the agent to the surface of the land along which it moves", with KE = ½mv². Energy depends on mass as well as speed, so glaciers, though slow, are more effective agents of erosion than wind because of their enormous mass. Of the five agents, wind, running water and glaciers are controlled by climate; waves and groundwater are not (Table 6).

Deposition is a consequence of erosion. Agents lose velocity, and so energy, on gentler slopes, and their load settles. NCERT stresses that "deposition is not actually the work of any agent". Coarser materials are deposited first and finer ones later, and depressions fill up. The same five agents act as depositional (aggradational) agents.

Human influence

NCERT's opening section notes that the surface has been shaped over very long periods, and that "humans have caused extensive damage to the environment through over use of resources", diminishing its potential at a fast rate. Several of NCERT's nine activating causes of mass movement are human: removal of support from below, artificial filling, explosions and machinery, drawdown of reservoirs and removal of vegetation.

Human activity also speeds erosion. A global compilation of studies found that erosion from conventionally ploughed agricultural fields averages one to two orders of magnitude (roughly 10 to 100 times) higher than rates of soil production, erosion under native vegetation and long-term geological erosion (Montgomery, PNAS, 2007).

Soil formation

Soil is a dynamic medium in which chemical, physical and biological activity goes on constantly. NCERT calls it "a result of decay" and "also the medium for growth". Pedology is soil science.

Process (pedogenesis). Soil formation depends first on weathering: the weathering mantle is the basic input. The weathered material or transported deposit is first colonised by bacteria and simple plants such as mosses and lichens. Dead remains build up humus. Grasses and ferns follow, then bushes and trees from seeds brought by birds and wind. Roots penetrate, burrowing animals bring up particles, and the material becomes porous and sponge-like, able to hold water and let air pass. The result is a mature soil, a complex mixture of mineral and organic products.

Factors (Table 7) act together and affect one another.

  • Parent material (passive) can be weathered rock in place (residual soils) or transported deposits (transported soils). Similar bedrocks may carry different soils and different bedrocks similar soils, but young soils and soils on some limestones show a strong link to the parent rock.
  • Topography (passive) works through sunlight exposure and drainage. Soils are thin on steep slopes and thick on flat uplands; gentle slopes with slow erosion and good percolation are most favourable. Flat areas may develop a thick clay layer rich in organic matter and dark in colour.
  • Climate (active) works through moisture and temperature. Excess water moves soil components downward (eluviation) and deposits them lower down (illuviation). In wet equatorial climates calcium, sodium, magnesium, potassium and much of the silica are removed; removal of silica is desilication. In dry climates evaporation exceeds precipitation, groundwater rises by capillary action and leaves salts that form a crust called a hardpan. In tropical climates with intermediate rainfall, calcium carbonate nodules (kankar) form. Chemical activity rises with temperature, falls in cool conditions (except carbonation) and stops at freezing; tropical soils therefore have deeper profiles, while tundra soils are mostly mechanically broken material.
  • Biological activity (active) adds organic matter, moisture retention and nitrogen. Humus accumulates in cold climates, where bacteria work slowly, and peat forms in sub-arctic and tundra climates. In humid tropical and equatorial climates bacterial action is intense, dead vegetation oxidises quickly and humus is low. Bacteria fix atmospheric nitrogen; Rhizobium lives in the root nodules of leguminous plants and fixes nitrogen for the host. Ants, termites, earthworms and rodents rework the soil mechanically, and earthworms change its texture and chemistry as it passes through them.
  • Time (passive) decides maturity. Soils on recent alluvium or glacial till are young and show no or poorly developed horizons. No fixed absolute time can be given for a soil to mature.
Explainer

Soil formation vs soil-forming factors. NCERT asks how the two differ. The process is the sequence by which weathered material becomes soil: colonisation by bacteria, mosses and lichens, humus build-up, plant succession, mixing by roots and animals, and finally a mature profile. The factors are the conditions that control how fast and in what direction the process runs. Climate and biological activity are active factors because they drive change: water moves material through the profile, and organisms add humus and nitrogen. Parent material, topography and time are passive: they set the starting point and the conditions but do not themselves drive the change.

PART 3 — UPSC Integration

PYQ pattern (from the bank)

Paper, yearBank IDQuestion
Mains GS1 2013 (5M)gs1-pyq-2013-22a"Bring out the causes for more frequent occurrence of landslides in the Himalayas than in the Western Ghats."
Mains GS1 2016 (12.5M)gs1-pyq-2016-14"The Himalayas are highly prone to landslides. Discuss the causes and suggest suitable measures of mitigation."
Mains GS1 2021 (10M)gs1-pyq-2021-06"Differentiate the causes of landslides in the Himalayan region and Western Ghats."
Mains GS3 2019 (15M)gs3-pyq-2019-19Hazard zonation mapping for landslide mitigation
Mains GS3 2021 (15M)gs3-pyq-2021-19Causes and effects of landslides; components of a National Landslide Risk Management Strategy

The same Himalaya-versus-Western-Ghats comparison has been asked three times in GS1. No Prelims question on this chapter is in the bank.

Mains frameworks

  1. Landslide causes = slope conditions + activating causes. Use NCERT's favouring conditions (weak materials, steep slopes, heavy rain, scarce vegetation) and its nine activating causes, then separate natural from human causes.
  2. Himalaya vs Western Ghats. Tectonic activity and weak sedimentary or unconsolidated rocks in the Himalaya; steep cliffs, strong temperature-driven mechanical weathering and intense short-duration rain on hard rock in the Ghats and Nilgiris (NCERT's box).
  3. Process-to-landform chain. Weathering prepares, mass movement and erosion remove, deposition builds, with climate selecting the dominant process.
UPSC Connect

Cross-paper relevance

  • GS1 (Geography): classification of geomorphic processes; landslide causes in the Himalaya and Western Ghats; soil formation.
  • GS3 (Disaster management): landslide hazard zonation and national strategy (gs3-pyq-2019-19, gs3-pyq-2021-19). Use GSI's figure of about 0.42 million km² (12.6% of land area) prone to landslides, as quoted by NDMA (2025), and recent events such as Wayanad (30 July 2024).
  • GS3 (Agriculture, environment): accelerated erosion under ploughing (Montgomery, 2007) and soil degradation.

Exam Strategy

Prelims fact-traps (NCERT text and exercises):

  • In NCERT, gradation is wearing down of relief through erosion. Its exercise asks which of deposition, diastrophism, volcanism and erosion is a gradational process; on NCERT's definition the answer is erosion. Texts that treat gradation as degradation plus aggradation would also count deposition, and diastrophism and volcanism are endogenic, so they are wrong either way.
  • Hydration is the chemical addition of water: calcium sulphate turns to gypsum, clay minerals swell and shrink, and salts in pore spaces undergo rapid, repeated hydration (pre-2022 text). Granite and quartz are not the materials NCERT associates with it.
  • Debris avalanche is a rapid flow mass movement, not a landslide.
  • Exfoliation is a result, not a process. Exfoliation domes come from unloading; tors from thermal expansion.
  • Mass movement is not erosion: no agent carries the debris.
  • Weathering is not a prerequisite for mass movement or for erosion, though it helps both.
  • Deposition is not the work of any agent; coarse material settles first.
  • Endogenic energy sources are radioactivity, rotational and tidal friction, and primordial heat.
  • Diastrophism includes earthquakes and plate tectonics, not only orogeny and epeirogeny.
  • Landslide material is relatively dry; slump has backward rotation; debris slide does not.
  • Of the five erosional agents, waves and groundwater are not climate-controlled.
  • Active soil factors: climate and biological activity. Passive: parent material, topography, time.
  • Chemical activity falls in cool conditions except carbonation.

Mains question patterns:

  • Comparative landslide questions (Himalaya vs Western Ghats) want NCERT's box points, set out side by side.
  • "Causes and mitigation" questions want NCERT's nine activating causes followed by measures such as hazard zonation mapping, slope stabilisation, drainage and vegetation cover.
  • "Earth is a playfield" style questions want endogenic and exogenic processes with their energy sources and effects.

Practice Questions

  1. Mains GS1 2013 (5 marks), bank ID gs1-pyq-2013-22a: "Bring out the causes for more frequent occurrence of landslides in the Himalayas than in the Western Ghats."
  2. Mains GS1 2016 (12.5 marks), bank ID gs1-pyq-2016-14: "The Himalayas are highly prone to landslides. Discuss the causes and suggest suitable measures of mitigation."
  3. Mains GS1 2021 (10 marks), bank ID gs1-pyq-2021-06: "Differentiate the causes of landslides in the Himalayan region and Western Ghats."
  4. Mains GS3 2021 (15 marks), bank ID gs3-pyq-2021-19: "Describe the causes and effects of landslides. What are the important components of a National Landslide Risk Management Strategy?"
  5. Practice (UPSC-pattern, not a past paper): With reference to geomorphic processes, consider the following statements: 1. Exfoliation domes result from thermal expansion. 2. Mass movements do not come under erosion. 3. Debris avalanche is a rapid flow mass movement. Which of the statements given above are correct? (Answer: 2 and 3 only. Exfoliation domes result from unloading.)

📦 Revision Capsule

Revision Capsule

Hard Facts

  • Current NCERT: Chapter 5 (Reprint 2026-27); Chapter 6 in pre-2022 editions.
  • Endogenic energy: radioactivity, rotational and tidal friction, primordial heat. Exogenic energy: the Sun, through the atmosphere, plus tectonic gradients.
  • Diastrophism: orogeny, epeirogeny, earthquakes, plate tectonics.
  • Gradation (NCERT): wearing down of relief through erosion. Denudation: weathering, mass wasting, erosion and transportation.
  • Chemical weathering: solution, carbonation, hydration, oxidation, reduction.
  • Exfoliation is a result, not a process; domes from unloading, tors from thermal expansion.
  • Enrichment: weathering concentrates ores of iron, manganese, aluminium and copper.
  • Mass movement forms: heave, flow, slide. Landslide types: slump, debris slide, debris fall, rockslide, rock fall; material relatively dry.
  • Debris avalanche: rapid flow mass movement, faster than mudflow.
  • Erosional agents: wind, running water, glaciers (climate-controlled); waves, groundwater (not).
  • Soil factors: climate and biological activity active; parent material, topography, time passive.
  • Desilication, eluviation, illuviation, hardpan, kankar, peat, Rhizobium.
  • About 0.42 million km² (12.6% of India's land) landslide-prone (GSI, quoted by NDMA, 2025).

Core Concepts

  • The surface is uneven because endogenic building and exogenic wearing never stop.
  • Weathering loosens in place; mass movement shifts under gravity; erosion carries by agents.
  • Climate and rock structure together set the rate of exogenic processes.
  • Weathering is the input for soil, erosion, mass movement and ore enrichment.
  • The Himalaya's landslides come from tectonic activity and weak rocks; the Ghats' from steep cliffs, intense rain and mechanical weathering on hard rock.

Confused Pairs

  • Weathering (in situ) vs erosion (transport by an agent) vs mass movement (gravity, no agent).
  • Exfoliation dome (unloading) vs tor (thermal expansion).
  • Slump (backward rotation) vs debris slide (no rotation).
  • Rockslide (substantial depth) vs rock fall (superficial layers).
  • Eluviation (washing down) vs illuviation (deposition below).

PYQ Pattern

  • Mains GS1: Himalaya vs Western Ghats landslides (2013, 2021); Himalayan landslide causes and mitigation (2016).
  • Mains GS3: landslide hazard zonation (2019); landslide risk management strategy (2021).

Sources

Sources