Geomorphology

Study of landforms, their processes, and the forces that shape Earth’s surface.

Author

Geography Team

Official Syllabus

NEP-2020 Syllabus

NoteCore I Paper IX — Geomorphology

**(4 Credit, Theory: 45hrs, Practical: 30hrs)*

**Unit I — Applied Geomorphology*

  • Applied Geomorphology: Nature, Scope and Significance
  • Principles of Geomorphology
  • Modern Techniques in Geomorphology: Profile, Hypsometry, Altimetry and Clinographic
  • Drainage Basin: Network Characteristics, Morphology, Phases of Development
  • Major Landforms: Fluvial, Aeolian, Glacial, Karst and Coastal

**Unit II — Environmental Geomorphology*

  • Environmental Geomorphology: Meaning and Application
  • Natural Hazards and Environmental Management
  • Geomorphic Hazards: Volcanic, Earthquakes, Landslide and Floods
  • Anthropogenic Activities and Effects on Erosion and Sedimentation
  • Urban Geomorphology and Application in Urban Planning
  • Concept of Economic Geomorphology

**Unit III — Case Studies in Applied Geomorphology*

  • Geomorphic Application in Soil Studies
  • Geomorphology and Disaster Management
  • Geomorphology in Engineering Construction (Dams, Roads, Tunnels)
  • Coastal Geomorphology and Management
  • Land Degradation and Restoration
  • Sustainable Geomorphological Practices

UGC NET Syllabus

TipUnit I — Geomorphology
  • Fundamental concepts of geomorphology
  • Factors controlling landform development
  • Endogenetic and exogenetic forces
  • Denudation processes: weathering and erosion
  • Geosynclines
  • Mountain building
  • Continental drift and plate tectonics
  • Concept of the Geomorphic Cycle
  • Landforms associated with: Fluvial, Glacial, Arid, Coastal, Karst cycles
  • Slope forms and processes
  • Environmental and Applied Geomorphology

Welcome to the Geomorphology module of Geography OpenCourseWare.

Part A: Common Topics (NEP-2020 & UGC NET)

These topics are covered in both the NEP-2020 undergraduate syllabus and the UGC NET syllabus.

Solar System and Earth as a Planet

The Solar System

  • Nebula: In space, thin gas forms clouds of enormous dimensions.
  • Akashganga / Milky Way: Our solar system belongs to this galaxy (approx. 100,000 million stars).
    • Light takes 8 minutes 32 seconds to reach Earth from the Sun.
    • Nearest star next to Sun is Proxima Centauri (4.3 light years).
  • 1 Light Year = 9,460,800,000,000 km (at light speed 300,000 km/s).
  • Gravitational Pull of Sun: 28 times higher than Earth’s.
  • Sun’s composition: 70% Hydrogen (H), 28% Helium (He).
    • Layers: Photosphere → Chromosphere → Corona (outermost layer).
  • Sun’s revolution speed: 220 km/second; one revolution ≈ 250 million years (Cosmic Year).

Dwarf Planets

  • Xena (UB 313): 10th planet of solar system discovered in 2005.
  • 24th August 2006: International Astronomical Union (IAU) introduced ‘Dwarf Planet’ category.
    • Pluto and Xena excluded from the 8 main planets.

Planet Discovery Timeline

Planet Discovery Year
Uranus 1781
Neptune 1846
Pluto 1930
Xena (UB313) 2003

Inner vs Outer Planets

  • Inner Planets: Mercury (57.9m km from Sun, 88-day revolution), Venus (Earth’s twin), Earth (‘Blue’ Planet), Mars (Red Planet, satellites Phobos & Deimos).
  • **Outer Planets:*
    • Jupiter: King of planets (318× Earth mass); fastest rotating (9 hrs 55 min); 63 satellites (Io, Europa, Ganymede, Callisto).
    • Saturn: 95× Earth mass; Rings A to G; 10 hrs 40 min rotation.
    • Uranus: 27 satellites (Titania & Oberon).
    • Neptune: twin of Uranus; 13 satellites (Triton & Nereid).
  • Asteroids: Thousands of small planets between Mars and Jupiter.

Earth as a Planet

  • Dimensions: Equatorial radius = 6378.2 km; Polar radius = 6356 km.
  • Geoid: True shape of earth (coined by Listing, 1873).
  • Summer Solstice: June 21 (first measured by Eratosthenes).
  • Circle of Illumination: Line that divides earth into day and night.
  • Earth Rotation: 365 days, 5 hours, 48 minutes, 45.68 seconds.

Earth’s Orbit

  • Shape: Elliptical; Total orbit: 943 million km; Speed: 29.8 km/s.
  • Perihelion: January 3 — 147.3 million km (closest to Sun).
  • Aphelion: July 4 — 152 million km (farthest from Sun).

Time and Measurement

  • Solar Day: 24 hours.
  • Sidereal Day: 23 hours 56 min 4 secs.
  • Greenwich Meridian (GMT): Established 1884; Royal Observatory (0°).
  • International Date Line: 180°; change of date discovered by Ferdinand Magellan.
  • IST (India): GMT + 5:30 (82½°E passing through Allahabad).

Origin and Age of the Earth

Origin of the Earth

Year Hypothesis Propounder Key Concept
1745 Buffon Hypothesis Buffon Comet collided with sun (1st scientific hypothesis)
1755 Gaseous Hypothesis Immanuel Kant Based on law of gravitation; “Give me matter and I will show you how to make a world”
1796 Nebular Hypothesis Laplace Exposition of the World System; cooling nebula
1904 Planetesimal Hypothesis Chamberlin Biparental concept; collision with a passing star
1919 Meteor Hypothesis Lockyer British proposal
1928 Tidal Hypothesis Harold Jeffreys “Filament” ejected from sun
1937 Binary Star Hypothesis H.N. Russell Companion star approaching
1943 Inter-Stellar Dust Otto Schmidt Capture of dust by sun
1955 Nova Hypothesis F. Hoyle Supernova explosion
— Big Bang Theory Edwin Hubble Expansion of the universe (Stephen Hawking)

Age of the Earth

Various methods have been used to estimate the age of the Earth:

Method Description
Radioactive Theory Most accurate; based on disintegration process (Pierre Curie, 1903).
Tidal Method Based on Moon moving away (approx. 13 cm/year). Estimate: ~2.95 billion years.
Salinity Method Age of Ocean = Total salt ÷ Annual rate of increase.
Sedimentation Total thickness of layers ÷ Annual rate of deposition (J. Murray).
Erosion Method Based on the rate at which land surfaces are lowered.
Evolution of Life Based on the complexity of the fossil record.
Kelvin’s Method Based on the rate of cooling of the Earth (1°C increase per 32m depth).

Geological Time Scale

The Geological Time Scale is the chronological programming of geological forms by their place of origin, evolution, and extinction.

  • First Scale: 1760, Giovanni Arduina.
  • Common Scale: 1881, adopted by the International Geographical Congress.
  • Hierarchy: Eon → Era → Period → Epoch → Age.

1. Precambrian (Cryptozoic)

  • Hadean (4600–4000 Ma): Volcanic activity, dawn of life.
  • Archean (4000–2500 Ma): Worms, algae, sponges; sea water had no salt.
  • Proterozoic (2500–541 Ma): Continental uplift at the end.

2. Paleozoic (Primary Era)

Period Age (Ma) Key Features
Cambrian 541–488 Ancient name of Wales; all animals in sea (Trilobites, corals).
Ordovician 488–443 Great mountain disturbance; volcanic activity in N. America.
Silurian 443–416 Caledonian Mountain building; first jawed fishes.
Devonian 416–359 Age of Fishes; first forests; “Dunkleosteus” armed fishes.
Carboniferous 359–299 Coal deposits; formation of Gondwanaland; Tethys Sea.
Permian 299–251 Appalachian Mountain building; coniferous forests.

3. Mesozoic (Medieval Life)

Period Age (Ma) Key Features
Triassic 251–199 Tethys extended; first dinosaurs and marsupials.
Jurassic 199–145 ‘Jura’ mountains; Humboldt first used the term; dinosaurs maximized.
Cretaceous 145–66 ‘Creta’ means chalk; extinction of reptiles; Deccan Lava.

4. Cenozoic (New Life)

The Tertiary period consists of five epochs in chronological order (ancient to recent): Paleocene → Eocene → Oligocene → Miocene → Pliocene.

Epoch Age (Ma) Key Features
Paleocene 66–56 Rocky Mountains formed; rat-like mammals appeared.
Eocene 56–33 Dawn of recent life; elephants appear for the first time.
Oligocene 33–23 Flowering plants; monkeys appeared; “Anthropoid” ancestors.
Miocene 23–5.3 Alps and Himalayas rise to maximum heights.
Pliocene 5.3–2.5 Gangetic plains formed; Australopithecus fossils.
Pleistocene 2.5–0.01 Great Ice Age (Gunz, Mindel, Riss, Wurm); ancestral ape-man.
Holocene 0.01–Pres. Melting of snow; ocean levels raised; the inter-glacial period.

Fundamental Concepts of Geomorphology

Warning📘 Syllabus Coverage
Syllabus Topic Details
NEP-2020 Geomorphology section — Fundamental concepts
UGC NET Unit I — Fundamental concepts

The Ten Fundamental Concepts (Thornbury)

  1. Uniformitarianism: The same physical processes operating today operated throughout geologic time, though not always with same intensity. “Present is the key to the Past” — Hutton (1785).
  2. Geological Structure: Structure is a dominant control factor in the evolution of landforms. Davis stated: “Landforms are a function of Structure, Process & Stage”.
  3. Differential Rates: Geomorphic processes operate at different rates on the Earth’s surface, creating varied relief.
  4. Distinctive Imprints: Each geomorphic process leaves its own characteristic assemblage of landforms (e.g., glacial vs. fluvial).
  5. Orderly Sequence: As erosional agents act on the surface, they produce an orderly sequence of landforms (Youth, Maturity, Old Age).
  6. Complexity of Evolution: Complexity in landform history is more common than simple, single-process evolution.
  7. Geological Age: Little of the Earth’s topography is older than the Tertiary; 90% of the present landscape is post-Tertiary (Pleistocene).
  8. Pleistocene Influence: Proper interpretation of the present landscape is impossible without considering the massive impacts of Pleistocene glaciations.
  9. Climatic Control: Appreciation of world climates is necessary to understand the varying importance of different geomorphic processes (e.g., arid vs. humid).
  10. Historical Extension: Geomorphology attains maximum usefulness by historical extension—studying the past to understand the present (Paleogeomorphology).

Key Historical Milestones

  • 1785: James Hutton — Theory of the Earth (Uniformitarianism).
  • 1802: John Playfair — Illustrations of the Huttonian Theory.
  • 1830: Charles Lyell — Principles of Geology.
  • Mid-1880s: The term “Geomorphology” was formally introduced.
  • 1899: W.M. Davis — Geographical Cycle.
  • 1924: Walther Penck — Morphological Analysis.

Evolution of Geomorphic Concepts (Chronology)

  1. Principle of Uniformitarianism (James Hutton, 1785)
  2. Theory of Continental Drift (Alfred Wegener, 1912)
  3. Theory of Convection Current (Arthur Holmes, 1928)
  4. Dynamic Equilibrium Theory (John Hack, 1960)

Earth’s Interior and Isostasy

Warning📘 Syllabus Coverage
Syllabus Topic Details
NEP-2020 Geomorphology — Interior of the Earth
UGC NET Unit I — Earth’s interior and Isostasy

1. Interior of the Earth

  • Density: Average density of Earth = 5.51 g/cm³.
  • Temperature Gradient: Increases 1°C per 32 meters depth in the crust.
  • Evidence Sources: Density, Pressure, Temperature, Volcanicity, and Seismology.

Seismic Waves

  • P-waves (Primary): Compressional waves; travel through solids, liquids, and gases (8–14 km/s).
  • S-waves (Secondary): Shear waves; travel only through solids (4 km/s).
  • Shadow Zone: S-waves disappear at an angular distance of 103°–120° from the epicenter, proving the core is liquid/semi-liquid.

Internal Structure (Discontinuities)

  1. Crust: Sial (Silica + Aluminium).
  2. Moho Discontinuity: Between Crust and Mantle.
  3. Mantle: Sima (Silica + Magnesium); contains the Asthenosphere.
  4. Gutenberg Discontinuity: Between Mantle and Core.
  5. Core: Nife (Nickel + Iron); Outer core is liquid, Inner core is solid.

2. Isostasy

Isostasy (Greek: Isostasios = State of Balance) refers to the mechanical stability between the Earth’s crust and the mantle.

  • C.E. Dutton (1889): First to coin the term.
  • Bouguer (1735): Noticed gravity anomalies during the Andes expedition.
  • George Everest: Discovered the discrepancy between triangulation and astronomical surveys in the Himalayas.

Major Theories of Isostasy

Scholar Theory Concept
Sir George Airy Law of Flotation “Uniform density with varying thickness.” Higher mountains have deeper roots (like icebergs).
Archdeacon Pratt Level of Compensation “Uniform thickness with varying density.” Heavier rocks (oceans) are denser than lighter rocks (mountains).
Hayford & Bowie Compensation Depth Calculated a “depth of compensation” at approx. 112 km.
Joly Compensation Zone Suggested a zone of compensation rather than a single level.
Arthur Holmes Root Theory Supported Airy’s view of deep crustal roots.

Endogenetic Forces: Volcanoes, Earthquakes, Folds, and Faults

Warning📘 Syllabus Coverage
Syllabus Topic Details
NEP-2020 Geomorphology — Endogenetic and exogenetic forces
UGC NET Unit I — Endogenetic forces (V/E/F/F)

1. Volcanicity

  • Tephra: Fragmented volcanic material.
  • Magma: Mixture of Silica (37–75%), Oxygen, and Gases.

Types of Volcanoes (by Eruption)

  • Hawaiian: 1200°C; basaltic lava, easy flow.
  • Strombolian: 1000°C; “Lighthouse of Mediterranean”.
  • Vulcanian: Cauliflower-shaped ash clouds.
  • Vesuvian / Plinian: Violent blasts of gas and ash.
  • Pelean: 800°C; most violent (Mont Pelée).

Volcanic Landforms

  • Extrusive: Ash cones, Composite cones (Strato), Calderas, Lava Plateaus (Deccan). Lapilli is a fragmented product specifically associated with volcanic eruptions. The Rajmahal Hills, formed by the eruption of basalts from the Kerguelen Hotspot about 100 million years ago, are partly connected to it by the 90-E ridge. Cocos Island is notably NOT a hotspot (unlike Easter, Tristan da Cunha, or Réunion).
  • Intrusive: Batholiths (largest), Laccoliths (dome), Lopoliths (saucer), Phacoliths (wave), Sills (horizontal), Dykes (vertical).

2. Earthquakes

  • Focus: Point of origin. Epicenter: Point on surface directly above focus.
  • Measurement:
    • Richter Scale (1935): Magnitude (logarithmic 0–9).
    • Mercalli Scale (1902): Intensity (Roman numerals I–XII).
  • Elastic Rebound Theory (H.F. Reid): Explains how energy is stored in rocks and released during an earthquake.
  • Dip: The value of apparent dip of a sedimentary stratum is always lower than the true dip.
  • Mass Movements: Lahars are a specific type of mass-movement (mudflow) associated with volcanoes.
  • Earth’s Magnetism: The magnetic property of the earth primarily results from convective movement in the outer core.

Key Phenomena

  • Liquefaction: Saturated sands behaving like liquid.
  • Tsunami: Harbour waves caused by sub-marine quakes.
  • Seismic Gap: Region of low activity prone to future major quakes (e.g., Central Gap in Himalayas).

3. Folds

Rock strata under horizontal compression. - Anticline: Arch-shaped upfold. Syncline: Trough-shaped downfold.

Fold Type Description
Symmetrical Both limbs equally bent (e.g., Zagros Mts).
Asymmetrical One limb is steeper than the other.
Overturned Axial plane is inclined and both limbs of the fold dip in the same direction.
Monoclinal One limb is vertical.
Recumbent Fold is pushed over so far that axial plane is horizontal.
Nappe Overthrust fold where a sheet of rock has moved miles (e.g., Alps).
Plunge Fold When the axis of the fold is tilted and forms an angle between the axis and the horizontal plane.
Plunging Syncline Two cuestas converging in the direction of plunge with dipslopes facing each other.

4. Faults

Fractures in the crust along which displacement occurs. - Normal Fault: Due to tension; Hanging wall moves downward relative to the foot wall. Creates Rift Valleys (e.g., Great Rift Valley of Africa, Rhine Valley). - Reverse Fault: Due to compression; creates Horsts / Block Mountains (e.g., Black Forest, Vosges). - Thrust Fault: Similar to reverse faults but with a very low dip angle; typically accommodates shortening in the earth’s crust. - Lateral / Strike-slip: Horizontal movement (e.g., San Andreas Fault). - En-echelon Faulting: Series of short, parallel faults that overlap like shingles on a roof. - Imbricate Thrusting: A series of closely spaced thrust faults dipping in the same direction. - Ramp Valley: Brahmaputra Valley (Assam).

Denudation Processes: Weathering and Mass Wasting

Warning📘 Syllabus Coverage
Syllabus Topic Details
NEP-2020 Geomorphology — Denudation processes
UGC NET Unit I — Weathering and mass wasting

1. Weathering

Weathering is the in-situ disintegration and decomposition of rocks. - **Denudation = Weathering + Erosion + Transportation.*

Physical (Mechanical) Weathering

  • Insolation / Block Disintegration: Expansion/contraction due to temperature.
  • Exfoliation: “Onion weathering” where outer layers peel off. An Exfoliation dome develops mainly due to pressure release stress resulting from denudation.
  • Frost Shattering: Water expands 10% when freezing.
  • Unloading / Pressure Release: Removal of overlying rock.

Chemical Weathering

  • Oxidation: Reaction with oxygen (rusting). Redox potential regulates the alternation of oxidation state from ferrous to ferric oxides.
  • Carbonation: CO₂ in water forms carbonic acid, dissolving limestone.
  • Hydration: Minerals absorb water and expand (e.g., Gypsum).
  • Solution: Direct dissolution of minerals (e.g., Rock salt). Note that Muscovite is typically dissolved by alkaline solutions.
  • Ideal Conditions: A hot and humid climate provides the most ideal conditions for the chemical weathering of rocks.

Soil Textures

  • Clay: Represents grains of < 2 μm. Unweathered stones at the base of a soil profile are associated with the R horizon.

2. Mass Wasting

Movement of rock waste downslope under the direct influence of gravity (Sharpe, 1938). Weathering contributes to mass movement by increasing water holding capacity, reducing shear strength, and breaking particles (it does not directly contribute via the winnowing of finer particles, which is wind action).

Slow Flowage

  • Soil Creep: Slow downhill movement of moist regolith under sustained shear stress without heaving (e.g., observed when trees and posts lean towards the direction of the slope). Trunks of trees growing on the banks of natural water bodies often take U-shaped bends primarily due to the creep of the bank materials.
  • Solifluction: Flow of water-saturated debris over permafrost.

Rapid Flowage

  • Earthflow: Rapid movement of saturated soil.
  • Mudflow: High-velocity flow of mud and water (Eliot Blackwelder, 1928).
  • Lahar: Volcanic debris flow.

Landslides

  • Slump: Rotational slip of a block.
  • Rockfall / Debris Fall: Free-falling material from steep cliffs.
  • Rockslide: Rapid sliding of rock along a plane of weakness.

*(Note: Mass movement types in order of increasing dryness: Solifluction -> Mudflow -> Creep -> Rockslide)

Continental Drift, Plate Tectonics, and Sea Floor Spreading

Warning📘 Syllabus Coverage
Syllabus Topic Details
NEP-2020 Geomorphology — Continental drift and plate tectonics
UGC NET Unit I — CD, Plate Tectonics, Sea Floor Spreading

1. Continental Drift Theory

  • Alfred Wegener (1912): Book “Die Entstehung der Kontinente und Ozeane”.
  • Pangaea: The supercontinent (All Earth) surrounded by Panthalassa (All Ocean).
    • Split into Laurasia (North) and Gondwanaland (South).
  • **Evidence:*
    • Jig-Saw Fit: Coasts of South America and Africa.
    • Glacial Evidence: Carboniferous glaciations in India, Australia, S. Africa.
    • Fossil Evidence: Mesosaurus and Glossopteris across southern continents.

2. Sea Floor Spreading

  • Harry Hess (1960): Proposed that new ocean crust is created at mid-ocean ridges.
  • Evidence: Magnetic anomalies (Vine and Matthews) and the age of ocean floor rocks (youngest at ridges, oldest near coasts).
  • Spreading Rates: Atlantic (1–1.5 cm/yr), East Pacific Rise (6 cm/yr), Max (18.3 cm/yr at Nazca-Pacific-Atlantic trijunction).

3. Plate Tectonics

  • Term ‘Plate’: First used by J. Tuzo Wilson (1965).
  • Theory Development: McKenzie, Parker, Morgan, and Xavier Le Pichon (1968).
  • Major Plates: Pacific, American, Eurasian, African, Antarctic, Indo-Australian.

Plate Margins

Type Process Example
Constructive Divergent / Spreading; Higher elevation of the mid-oceanic ridge relative to the flanking sea-floor is best explained by Airy’s theory of isostasy. Mid-Atlantic Ridge
Destructive Convergent / Subduction Nazca vs. South American (Andes)
Conservative Transform Fault; located along ocean-floor fracture zones and continental faults like San Andreas. San Andreas Fault
Wilson Cycle Model describing the stages of opening and closing of ocean basins. —

4. Isostasy vs Plate Tectonics

While Isostasy explains vertical balance, Plate Tectonics explains horizontal movement. Together they provide a complete framework for Earth’s surface dynamics.

Rocks: Types and Transformation

1. Igneous Rocks (Primary Rocks)

Formed from the cooling and solidification of magma/lava. - Intrusive (Plutonic): Solidified deep inside (Granite). - Extrusive (Volcanic): Solidified on the surface (Basalt). - Classification: - Felsic: High Feldspar/Silica. - Mafic: High Iron/Magnesium.

Intrusive Forms

  • Batholith: Largest bodies (>100 sq km).
  • Laccolith: Mushroom-shaped.
  • Lopolith: Saucer-shaped.
  • Sill: Horizontal sheet. Dyke: Vertical sheet.

2. Sedimentary Rocks

Formed by the accumulation and lithification of sediments. They cover 3/4 of the Earth’s surface but only 5% of its volume. - Argillaceous: Clay-based (Shale). - Arenaceous: Sand-based (Sandstone). - Calcareous: Lime-based (Limestone, Chalk). - Carbonaceous: Carbon-rich (Coal).

3. Metamorphic Rocks

Formed by the transformation of existing rocks under high temperature and pressure.

Original Rock Metamorphic Rock
Granite Gneiss
Limestone Marble
Sandstone Quartzite
Shale Slate
Coal Anthracite
Gabbro Serpentinite
Mica Schist

Geomorphic Cycle of Erosion

Warning📘 Syllabus Coverage
Syllabus Topic Details
NEP-2020 Geomorphology — Concept of geomorphic cycle
UGC NET Unit I — Geomorphic Cycle (Davis, Penck)

1. W.M. Davis: The Geographical Cycle (1899)

Davis proposed that landforms develop in a predictable sequence based on Darwinian principles. - Trio of Davis: “Landscape is a function of Structure, Process, and Time (Stage)”.

Stages of Erosion

  1. Youth: Stream lengthening, valley deepening, steep slopes, V-shaped valleys.
  2. Maturity: Lateral erosion begins, V-shaped valleys broaden, profile of equilibrium starts.
  3. Old Age: Base level of erosion reached; formation of a Peneplain (almost a plain) with residual hills called Monadnocks. The rate of erosion is minimal, and Entropy is maximised on the peneplain.
  • Etch-surface / Etchplain: A product of two phases of erosion (deep weathering followed by stripping of the saprolite). The deep weathering process is fundamentally linked to the formation of Etchplains.
  • Entrenched Meanders: A primary indicator of a rejuvenation process in a river valley.
  • Superimposed Profile: Drawn primarily to understand the cyclic nature of a landscape.
  • Relaxation Time: The time interval between two steady state or equilibrium conditions in a geomorphic system. *Note: The Hypsometric integral provides quantitative support for the idea of Davis’ three stages of landform development. A value of 0.18 denotes maximum erosion of a drainage basin area down to its base level.

2. Walther Penck: Morphological Analysis (1924)

Penck rejected Davis’s focus on “time” and emphasized the relation between uplift and degradation. - “Geomorphic forms are an expression of the phase and rate of uplift in relation to the rate of degradation”.

Penck’s Development Phases (Entwickelung)

  • Aufsteigende: Accelerating development (Uplift > Erosion).
  • Gleichformige: Uniform development (Uplift = Erosion).
  • Absteigende: Waning development (Erosion > Uplift).
  • Landform Features: Piedmont-trappen, Piedmontfläche, Haldenhang (wash slope), and Böschungen (gravity slope).

3. L.C. King: Pediplanation (1950s)

Based on studies in South Africa. - Pediment: An erosional slope cut into bedrock at the foot of a mountain. - Scarp Retreat: Parallel retreat of slopes. - Pediplain: Coalesced pediments forming a vast plain with residual Inselbergs.

4. Geomorphic Equilibria

Geomorphic systems tend towards a steady state, balancing inputs and outputs. - Dynamic Equilibrium: A state where small, frequent variations occur around a long-term unchanging mean (e.g., G.K. Gilbert’s concept of landscape equilibrium). - Metastable Equilibrium: A state of equilibrium that is interrupted by a sudden change due to a threshold being crossed (e.g., a sudden landslide after prolonged weathering), establishing a new equilibrium state. - Unstable Equilibrium: A state where a small disturbance leads to continuous, progressive change away from the original state. - Steady State: Ideal achievement of steady state in an open system occurs, for example, in a stretch of a river between two closely-spaced bridges.

Slope Forms and Processes

Warning📘 Syllabus Coverage
Syllabus Topic Details
NEP-2020 Geomorphology — Slope forms and processes
UGC NET Unit I — Slope forms and processes

1. Elements of Slope

According to Wood (1942) and L.C. King, a fully developed slope has four elements: 1. Waxing Slope (Upland Crest): Convex top. 2. Free Face (Scarp): Bedrock outcrop, vertical or near-vertical rock face. According to Wood’s model, the retreat of the free face in the initial stage results in the development of an upper rectilinear slope. 3. Debris Slope (Constant Slope / Talus): Accumulation of weathered material, retreats with free face. 4. Waning Slope (Pediment / Valley Floor): Concave base.

2. Pediment Formation Theories

A Pediment is a smooth, gently sloping erosional surface cut into bedrock at the base of a mountain.

Theory Scholar Year Key Concept
Sheetflood Theory McGee 1897 Formed by the erosive power of thin sheets of water after heavy desert rain.
Lateral Planation D.W. Johnson — Lateral erosion by shifting stream channels at the mountain foot.
Recession Theory Lawson 1915 Gradual recession of the mountain front (scarp retreat).
Composite Theory Kirk Bryan 1923 A combination of weathering, sheetflood, and lateral planation.

3. Slope Evolution Models

  • W.M. Davis (Slope Decline): Slopes become gentler over time as the landscape ages.
  • Walther Penck (Slope Replacement): Steep slopes are replaced by gentler ones from below (Haldenhang replaces Böschungen). A steep rectilinear slope without change of angle is specifically designated as Haldenhang.
  • L.C. King (Slope Retreat): Slopes maintain their angle but retreat backward (Parallel Retreat).

Fluvial Landforms and Drainage Systems

Warning📘 Syllabus Coverage
Syllabus Topic Details
NEP-2020 Geomorphology — Fluvial landforms
UGC NET Unit I — Fluvial landforms and drainage systems

1. Drainage Patterns and Stream Types

Stream Types (Johnson, 1932)

  • Consequent: Follows the initial slope (coined by J.W. Powell).
  • Subsequent: Follows belts of weaker rock (J.B. Jukes).
  • Obsequent: Flows opposite to the master consequent.
  • Antecedent: Maintains its original course despite upliftment (e.g., Himalayas rivers).
  • Superimposed: Established on a cover of rocks that has since been removed.

Major Drainage Patterns (A.D. Howard)

  • Dendritic: Tree-like (e.g., Indo-Gangetic Plain).
  • Trellis: Rectangular with long parallel main streams (e.g., Aravallis).
  • Radial: Flows outward from a central point (e.g., Ranchi Plateau).
  • Centripetal: Flows inward to a basin (e.g., Kathmandu Valley).

Fluvial Mechanics & Transport Capacity

  • Stream Competence: The measure of the maximum size of particles that a stream can transport.
  • Reynolds Number: The ratio of inertial force to viscous force in a fluid.
  • Hydraulic Geometry: In at-a-station hydraulic geometry equations (\(b + f + m = 1\)), if \(b = 0.22\) and \(f = 0.64\), the expected value of \(m\) is \(0.14\).
  • Suspended Sediment: High concentration of suspended sediment increases the transportational capacity of a stream because it increases viscosity, which reduces turbulence and energy dissipation.
  • Impoundment: The impoundment of a river (e.g., by a dam) decreases its downstream entrainment capacity because water velocity drops in the reservoir.
  • Tectonic Sinuosity: Sinuosity of an alluvial river decreases if slope increases due to tectonic movement. Channel slope usually increases downstream of an uplifting anticlinal axis.
  • Sediment Stratum: In a river terrace, a continuous stratum of pebbles within layers of sands indicates that the river was moving fast at the time of deposition.
  • Potholes: The formation of potholes in river beds is a classic example of Corrasion (Abrasion).
  • Helical Flow: A continuous spiral motion of water as it flows along a river channel.
  • Yazoo Stream: A tributary that flows parallel to the main stream for a distance before joining, often due to the presence of natural levees on the main stream.
  • Meander Chute Cut-off: Occurs when two meander necks do not come closer, but a channel from one neck joins the other and the main flow turns on that channel.
  • Channel Pattern Alteration: A river’s channel pattern may alter from braided to meandering due to a decrease in rainfall in its catchment area.
  • Horton’s Law of Stream Number: Confirms to the mathematical model of a Negative Exponential Function.

2. River Rejuvenation

Rejuvenation occurs when a river’s erosive power is restored. - Dynamic: Due to land uplift. - Static: Due to climate change or river capture. - Eustatic: Due to sea-level fall. - Topography: Knickpoints (waterfalls), valley-in-valley, and river terraces.

3. Waterfalls

Waterfall Feature Location
Angel Falls Highest (979m) Venezuela
Niagara Falls Cap rock fall USA/Canada
Hundru Falls Knickpoint fall Jharkhand, India
Victoria Falls Zambezi river Africa

4. Deltas (Herodotus)

The Ganga-Brahmaputra Delta is the world’s largest (125,000 sq km).

Delta Type Characteristics Examples
Arcuate Bow-shaped Nile, Ganga, Indus
Bird-foot Finger-like Mississippi
Estuarine In tidal estuaries Hudson, Mackenzie
Cuspate Tooth-shaped Tiber (Italy)
Abandoned Course shifted Huang He (Yellow River)

Glacial Landforms

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1. Types of Glaciers

  • Continental: Large ice sheets (Antarctica, Greenland).
  • Valley (Alpine): High mountain ranges.
  • Piedmont: Spread out at the foot of mountains (Malaspina, Alaska).

2. Erosional Landforms

  • Cirque / Corrie: Armchair-shaped hollow.
  • Tarn: Lake in a cirque.
  • Horn: Pyramid peak (Matterhorn).
  • U-shaped Valley / Glacial Trough: Broad floor with steep sides.
  • Hanging Valley: Tributary glacier valley above the main trough.
  • Fjord: Submerged glacial trough.
  • Roche Moutonnée: “Sheep-back” rock with one smooth side and one jagged side.

3. Depositional Landforms

  • Moraine: Lateral, Medial, and Terminal debris.
  • Drumlin: Whale-shaped mound (Basket of Eggs topography).
  • Erratics: Large boulders transported far from their source.

4. Glacio-Fluvial (Meltwater) Features

  • Melting: Involves both supraglacial (surface) and subglacial (beneath) processes.
  • Eskers (Osar): Sinuous ridges of sand/gravel.
  • Kames: Steep-sided hills of stratified drift.
  • Outwash Plain (Sandur): Flat plain of meltwater deposits.
  • Kettle Holes: Depressions formed by melting ice blocks.
  • Moulin: A vertical or nearly vertical shaft in a glacier, formed by surface water percolating through a crack in the ice.
  • Glaciated Valley Lake Sequence: From higher to lower altitudes, the landforms typically appear as Tarn → Paternoster lake → Moraine-dammed lake → Kettle lake.

Coastal Landforms

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1. Beach Zones

  • Shoreline: Line between low and high tide.
  • Backshore: Normally dry; only reached by storm waves.
  • Foreshore: Intertidal zone where wave breaking occurs.
  • Nearshore: Between breaker zone and low tide.
  • Offshore: Beyond the low tide line.

2. Erosional Landforms

  • Sea Cliff: Steep rock face.
  • Wave-cut Platform: Flat area at the base of a cliff.
  • Sea Cave: Hollowed out base of a cliff.
  • Sea Arch / Natural Bridge: Formed when caves on both sides of a headland meet.
  • Stack: Isolated pillar of rock.
  • Stump: Low-level eroded stack.
  • Geo / Inlets: Long narrow opening in the cliff.
  • Runnel: A linear depression or channel on a beach, often separated from the sea by a ridge.
  • Sediment Dynamics: Coasts tend to become sandy to muddy as the tidal range changes from micro to macro. Mangrove vegetation in tropical coasts is highly conducive to the deposition of fine sediments.

3. Depositional Landforms

  • Beach: Sandy or pebbly deposit.
  • Bar: Submerged or semi-submerged ridge of sand (Offshore bar).
  • Spit: A bar attached to the land at one end (e.g., Chilika lake mouth).
  • Hook: A curved spit.
  • Tombolo: A bar connecting an island to the mainland.
  • Lagoon: Enclosed shallow water body (e.g., Pulicat Lake).

4. Shoreline Classification (Johnson)

Type Cause Example
Submerged Sea level rise or land subsidence Fjord (Norway), Ria (Ireland), Dalmation (Yugoslavia).
Emerged Sea level fall or land upliftment Kerala Coast (India); characterized by bars and lagoons.
Neutral Deltaic or volcanic growth —
Compound Mixture of processes —

Karst Landforms

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Karst topography develops in regions with soluble rocks like Limestone, Dolomite, or Chalk.

1. Surface Features

  • Terra Rosa: Red residual clay on the surface.
  • Lapies: Deep grooves and ridges.
  • Cockpit: A star-shaped depression in Karst topography, typical of tropical Karst (e.g., Jamaica).
  • Sinkholes / Swallow Holes: Circular depressions where water disappears. By far the most common and widespread topographic form in a Karst terrain is the sinkhole, which varies in depth from less than a meter to a few hundred meters.
  • Hums: Residual hills found in Karst landscapes, representing the final stage of limestone dissolution.
  • Doline: A larger sinkhole.
  • Uvala: Coalesced dolines.
  • Polje: Largest Karst depression (huge flat floor).
  • Blind Valley: Valley that ends abruptly as stream sinks underground.

2. Underground Features

  • Caverns / Limestone Caves: Subterranean voids.
  • Stalactite: Icicle-like formation hanging from the ceiling.
  • Stalagmite: Pillar-like formation growing from the floor.
  • Cavern Pillar: When stalactite and stalagmite meet.
  • Speleothems: General term for all cave deposits.

3. Karst Cycle (Beede / Cvijic)

The karst cycle describes the evolution from early sinkhole development to the complete dissolution of limestone down to the base level. - Classic Region: Slovenia/Yugoslavia. - Indian Example: Sahastradhara in Dehradun, Uttarakhand.

Aeolian Landforms (Arid and Semi-Arid)

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1. Types of Desert Surface

  • Erg: Sandy desert (Sahara).
  • Reg: Stony desert (Algeria).
  • Hammada: Rocky desert (Sahara).
  • Sheet Flood: A major land-forming process in arid and semi-arid regions, occurring when high intensity, short duration rainfall causes water to flow as a broad sheet over the surface.

2. Erosional Landforms

  • Blow-out: Hollows formed by wind deflation.
  • Mushroom Rock (Gara / Pedestal Rock): Formed by abrasion near the ground.
  • Zeugen: Ridge-and-furrow landscape in layered rocks (erosional).
  • Yardang: Vertical rock ridges (erosional).
  • Mesa: A flat-topped hill with steep sides (erosional landform common in arid environments).
  • Inselberg (Bornhardt): Isolated residual hill in arid plains.
  • Demoiselles: Earth pillars.

3. Depositional Landforms (Sand Dunes)

Dune Type Features
Barchan Crescent-shaped with horns pointing downwind.
Transverse Perpendicular to wind direction.
Longitudinal (Seif) Parallel to dominant wind direction.
Parabolic U-shaped with horns pointing upwind (found in coastal areas).
Star Dune Star-shaped with multiple arms.

4. Loess

  • Loess: Fine, wind-blown silt deposited far from the desert source.
  • North China Loess: Extensively studied by Von Richthofen.
  • Loess covers approx. 10% of total land area (Peesi, 1968).

Plateaus and Plains

1. Plateaus

Plateaus cover about 33% of the Earth’s surface and house 9% of the world’s population.

Types of Plateaus

  • Intermontane: Surrounded by mountains (Tibet, Bolivia, Mexico).
  • Piedmont: Between mountain and plain/sea (Patagonia, Appalachian).
  • Volcanic: Formed by lava (Deccan, Columbia).
  • Dissected: Heavily eroded (Meghalaya Plateau).
  • Dome-shaped: Chota Nagpur Plateau.

Stages of Plateau Development (Davis)

  • Young: Mahabaleshwar.
  • Mature: Ranchi Plateau, Appalachians.
  • Old / Rejuvenated: Missouri Plateau.

2. Plains

Plains cover 41% of the land area and house 85% of the global population.

Types of Plains

  • Structural: Coastal plains (Malabar, Atlantic Coast).
  • Erosional:
    • Peneplains: (Davis) Almost flat plains.
    • Karst Plains: Limestone regions.
    • Glacial Erosion Plains: Scoured bedrock.
  • Depositional:
    • Alluvial: Flood plains, deltas (Indo-Gangetic).
    • Loess: Wind-blown silt (China).
    • Glacial Drift: Till plains.
    • Lava Plains: Flat volcanic surfaces.

Part B: NEP-2020 Specific Topics

These topics are part of the NEP-2020 undergraduate programme only.

Applied Geomorphology

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NEP-2020 Unit I — Applied Geomorphology; Unit III — Case Studies

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NoteKey Concepts
  • Nature and Scope: Application of geomorphic knowledge to solve practical problems in engineering, planning, and resource management.
  • Geomorphic Application in Soil Studies: Relationship between landforms and soil types; soil mapping using geomorphic analysis.
  • Engineering Geomorphology: Site selection for dams, roads, tunnels, bridges — terrain analysis for construction.
  • Urban Geomorphology: Understanding pre-existing terrain for urban planning; slope stability, flood risk, foundation conditions.
  • Economic Geomorphology: Mineral exploration, groundwater prospecting, sand and gravel extraction.
  • Coastal Management: Shoreline protection, beach nourishment, harbor siting.

Environmental Geomorphology

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NEP-2020 Unit II — Environmental Geomorphology

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NoteKey Concepts
  • Definition: Study of human impact on geomorphic processes and landforms, and natural hazards affecting human activities.
  • Anthropogenic Impacts: Effects of construction, mining, deforestation, agriculture on erosion, sedimentation, and landscape change.
  • Land Degradation and Restoration: Causes (overgrazing, deforestation, urbanization), assessment, and remediation strategies.
  • Sustainable Geomorphological Practices: Balancing development with landscape conservation.
  • Geomorphic Hazards: Volcanic eruptions, earthquakes, landslides, floods — hazard mapping and risk assessment.
  • Natural Hazards and Environmental Management: Disaster preparedness, mitigation strategies, early warning systems.

Drainage Basin Morphometry

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NEP-2020 Unit I — Drainage Basin: Network Characteristics, Morphology; Unit IV — Practical

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NoteKey Concepts
  • Drainage Basin: Fundamental geomorphic unit — area drained by a river and its tributaries.
  • Stream Ordering: Horton’s and Strahler’s methods of stream classification.
  • Morphometric Parameters:
    • Linear Aspects: Stream order, stream number, stream length, mean stream length ratio, bifurcation ratio
    • Areal Aspects: Drainage density, stream frequency, drainage texture, form factor, circularity ratio, elongation ratio
    • Relief Aspects: Basin relief, relief ratio, ruggedness number
  • Hypsometric Analysis: Hypsometric curve and integral — indicates stage of basin erosion. A hypsometric integral value of 0.92 denotes minimum erosion (youthful stage).
  • Clinographic Curve: Relationship between slope angle and area.
  • Altimetric Frequency Graph: Frequency distribution of elevations within a basin.
  • Applications: Flood prediction, watershed management, groundwater exploration, soil conservation.

Modern Techniques in Geomorphology

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NEP-2020 Unit I — Modern Techniques; Unit IV — Practical (RS, GIS, DEM)

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NoteKey Concepts
  • Remote Sensing: Satellite imagery and aerial photographs for landform identification and mapping.
  • GIS (Geographic Information Systems): Spatial analysis, terrain modeling, overlay analysis for geomorphic studies.
  • Digital Elevation Models (DEM): Generation, analysis, and visualization of terrain — SRTM, ASTER, LiDAR.
  • GPS and GNSS: Precise positioning for field surveys, monitoring ground displacement.
  • Profile Analysis: Longitudinal and transverse profiles of rivers and slopes.
  • Hypsometry and Altimetry: Quantitative terrain analysis using elevation data.
  • Geomorphic Mapping: Systematic mapping of landforms, processes, and deposits using standardized legends.

Part C: UGC NET Specific Topics

These topics are part of the UGC NET syllabus only.

Geosynclines and Mountain Building

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UGC NET Unit I — Geosynclines and mountain building

1. Geosynclines (Hall and Dana)

Geosynclines are long, narrow, and shallow water bodies which undergo gradual subsidence and sedimentation.

Types of Geosynclines (Schuchert)

  • Monogeosyncline: Narrow and shallow (e.g., Appalachian).
  • Polygeosyncline: Broad and complex (e.g., Rockies, Urals).
  • Mesogeosyncline: Mobile ocean basins between landmasses (e.g., Tethys).

2. Mountain Building (Orogenesis)

Classification by Age

  • Pre-Cambrian: Canadian Shield, Aravallis (oldest).
  • Caledonian: (Silurian-Devonian) Appalachians, Grampians.
  • Hercynian (Variscan): (Carboniferous-Permian) Black Forest, Vosges.
  • Alpine: (Tertiary) Himalayas, Alps, Andes, Rockies.

Major Theories of Orogeny

Theory Scholar Concept
Geosynclinal Theory Kober Orogenesis from geosynclines; median mass (Zwischengebirge).
Thermal Contraction Jeffreys Cooling Earth caused surface wrinkling (Mountains).
Thermal Convection Arthur Holmes Convection currents in the mantle drive crustal deformation.
Radioactive Theory Joly Radioactive heating/cooling cycles cause expansion/contraction.
Sliding Continents Daly Gravity-driven sliding of continental blocks.
Plate Tectonics — Collision of lithospheric plates (e.g., Indo-Eurasian collision).

Quick Reference

Geomorphology Quick Reference

Key Books and Authors

Book Author
Theory of the Earth Hutton (1788)
Principles of Geology Lyell (1830)
The Geographical Cycle Davis (1899)
Morphological Analysis Walther Penck (1924)
Morphology of the Earth L.C. King
Principles of Physical Geology Arthur Holmes
Principles of Geomorphology W.D. Thornbury
Water, Earth and Man Chorley (1969)

Theories and Propounders

Theory / Concept Propounder
Uniformitarianism James Hutton
Peneplain W.M. Davis
Continental Drift Alfred Wegener
Sea Floor Spreading Harry Hess
Plate Tectonics Wilson, Morgan, Le Pichon
Isostasy (Term) C.E. Dutton
Convection Currents Arthur Holmes
Geosynclines Hall and Dana
Big Bang Theory Edwin Hubble
Strahler Stream Order Arthur Strahler

Important Terms

  • Geoid: True shape of Earth.
  • Knickpoint: Point of sudden change in river profile (waterfalls).
  • Speleothems: Cave formations (stalactites/stalagmites).
  • Tephra: Volcanic debris.
  • Tsunami: Harbour waves.
  • Zwischengebirge: Kober’s median mass in mountain building.

Notes compiled by Pulakesh Pradhan — Geomorphology (NET)

Notes compiled by Geography Team

Key Scholars — Geomorphology

Contributors and Their Contributions (NET Notes — Pulakesh Pradhan)

Scholar Year Key Contribution
James Hutton 1785, 1788 Concept of Uniformitarianism; Theory of the Earth
Charles Lyell 1830 Principles of Geology
W.M. Davis 1899 The Geographical Cycle
Walther Penck 1924 Morphological Analysis
Richard Chorley 1969 Water, Earth and Man
L.C. King — Slope development; pediplanation
Wood 1942 Proposed 4 elements of a slope
J.W. Powell — Coined the term ‘Consequent’ river; concept of base level
Alfred Wegener 1912 Continental Drift Theory; Die Entstehung der Kontinente und Ozeane
Harry Hess 1960 Sea Floor Spreading theory
J. Tuzo Wilson 1965 Coined the term ‘Plate’
McKenzie, Parker, Morgan, Le Pichon 1968 Developed the Plate Tectonics Theory
C.E. Dutton 1889 Coined the term ‘Isostasy’
Bouguer 1735 Discovered gravity anomalies during Andes expedition
Listing 1873 Coined the term ‘Geoid’

Notes compiled by Pulakesh Pradhan — Geomorphology (NET)