Physical Geography

Comprehensive study of geomorphology, climatology, and oceanography.

Author

Geography Team

Official Syllabus (NEP-2020)

Note

Core I Paper I
(4 Credit, Theory: 45hrs, Practical: 30hrs)

Unit - I:
Learning Outcome : Comprehend the fundamentals of geomorphic processes, landforms, climate systems, and hydrology, enabling them to analyze and explain the interconnectedness of these elements within global ecosystems

Meaning, scope, and components of physical geography, Interior of the Earth; Origin of continents and oceans; Isostasy; Earthquakes and volcanoes; Earth movements; Faults, folds; Continental Drift and Plate Tectonic Theories; ; Cycle of erosion: Davis and Penck; Weathering and Mass Wasting.
Unit -II:
Learning Outcome:
Gain comprehensive understanding of the Earth’s atmospheric structure, composition, and characteristics, and be able to analyze and interpret climate patterns, factors influencing climate, and the impact of climatic changes on various ecosystems and human socie ties.

Elements of weather and climate; Structure and composition of atmosphere. Insolation and heat budget, vertical and horizontal distribution of temperature; Atmospheric pressure and winds - Air mass, Frontogenesis, Tropical CyLOne and Origin; and mechanism of Monsoon.
Unit -III: Learning Outcome:
Acquaint themselves with thorough understanding of the hydrological cycle, the movement and distribution of water across terrestrial and marine systems, allowing them to ocean bottom topography, ocean temperature and salinity, ocean currents, and sediment deposits.
Hydrological Cycle: Factors affecting run -off, infiltration and groundwater. Water Storage and Circulation; Ocean bottom topography; Temperature and salinity of ocean water; Ocean current and deposits.
Unit -IV: (Practical) Learning Outcome:
Honed their fieldwork and laboratory skills, enabling them to apply physical geographic methods to collect, analyze, and interpret data from real -world environments.
proficient in representing relief features such as Mountains, Valleys (U shaped and V shape), Waterfalls, Plateaus, and

  1. Drawing of Contour Features – Mountain, Valley (U shaped and V shape), Waterfall, Plateau and Escarpment;
  2. Calculation of time of place with reference to GMT;
  3. Introduction to use of simple weather observation instruments: Thermometer (Wet and dry bulb temperature), Barometer, hygrometer, anemometer, wind vane, Rain Gauge, Stevenson Screen,
  4. Interpretation of weather maps; Construction and interpretation hydrographs and unit hydrographs; T -S Diagram.
  5. Practical Record and Viva.

Geomorphology

Fundamental Concepts of Geomorphology

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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

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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

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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

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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

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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.

Geomorphic Cycle of Erosion

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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.

Fluvial Landforms and Drainage Systems

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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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NEP-2020 Geomorphology — Glacial landforms
UGC NET Unit I — Glacial landforms

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.

Slope Forms and Processes

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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).

Coastal Landforms

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NEP-2020 Geomorphology — Coastal landforms
UGC NET Unit I — Coastal landforms

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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NEP-2020 Geomorphology — Karst landforms
UGC NET Unit I — Karst landforms

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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NEP-2020 Geomorphology — Aeolian landforms
UGC NET Unit I — Aeolian landforms

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).

Climatology

Composition and Structure of the Atmosphere

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Monkhouse: *“The atmosphere is a thin layer of gas held to the earth by gravitational attraction.”

  • CO₂ — 1752: first gas to be studied (0.03%)
  • ‘Mephitic Air’ — 1772: Rutherford discovered Nitrogen gas (N₂)

Gaseous Composition (%)

Gas Extent Percentage
Nitrogen (N₂) Up to 100 km 78.03%
Oxygen (O₂) Up to 120 km; concentration at 16 km 20.99%
Argon (Ar) — (enters via radioactive breakdown) 0.94%
Carbon Dioxide (CO₂) Up to 32 km. Mainly from respiration and decomposition by biota. 0.03%
Hydrogen (H₂) Up to 1100 km 0.01%
Neon (Ne) — 0.0018%
Helium (He) — 0.0005%
Krypton (Kr) — 0.0001%
Xenon (Xe) — 0.000009%
Ozone (O₃) 12 to 50 km; absorbs UV-B wavelength 0.000001%
  • **Other Trace Gases:*
    • Methane (CH₄): Derived from enteric fermentation in animals and decomposition.
    • Nitrous Oxide (N₂O): Derived from microbial activity in soil.
  • Water Vapour — varies from 0–4%; less above 2000 meters
  • Dust Particles — hygroscopic nuclei; Smoke + Fog = **Smog*

Atmospheric Layers by Gas

Layer Altitude
Molecular Nitrogen Layer 90–200 km
Atomic Oxygen Layer 200–1100 km
Helium Layer 1100–3500 km
Atomic Hydrogen Layer 3500 km to outermost

Structure of the Atmosphere

Troposphere

  • Altitude: 0–8 km (poles) to 16 km (equator); Avg = 16 km
  • Lapse Rate: 1°C per 165 m (or 6.4°C per km). A negative lapse rate is synonymous with temperature inversion, where temperature increases with height.
  • Water vapour: 5000 ppm (lower) to 100 ppm (upper, 11–12 km)
  • Pressure: 1013 mb at sea level → 200 mb at 12 km
  • Density: 1 kg/m³ → 0.2 kg/m³ at top
  • Tropopause: 1.5 km thick; acts as an effective lid on convection; it is an isothermal layer.
    • Height varies latitudinally.
    • Average temperature ranges from −70°C to −85°C (at equator).
    • Average pressure is approximately 100 mb.
    • Discovered by WMO (World Meteorological Organization) — 1957.
  • Air Travel: Air travel from London to New York involves longer time than the return journey because of the resistance of the Upper air jet stream (headwinds).

Stratosphere

  • Altitude: up to 50 km; contains 10% of atmosphere mass
  • ‘Mother of Pearls’ or ‘Nacreous’ clouds found here
  • Ozone Layer: 15–35 km

Stratopause

  • At 50–55 km

Mesosphere

  • Temperature reaches −90°C at the top
  • Pressure: 1 mb at 50 km → 0.001 mb at 90 km

Thermosphere

  • Temperature: −90°C at 80 km → 120°C at 350 km

Ionosphere (80–400 km)

  • Aurora Borealis and **Aurora Australis*
Layer Altitude Function
D-layer 80–90 km Reflects low frequency radio waves
E-layer (Kennelly-Heaviside) 90–160 km Reflects medium frequency
F-layer (Appleton Layer) — Reflects medium to high frequency
G-layer Above 480 km —

Exosphere

  • Altitude: 500–750 km

Insolation and Heat Budget

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Insolation

  • Insolation = Incoming Solar Radiation
  • Averaged over a year, approximately 342 W of solar energy reaches every m² of Earth.
  • Solar radiation is mostly in the short wave range of < 4 µm. Solar wavelengths shorter than 0.285 µm hardly penetrate below 20 km altitude of the atmosphere.
  • Pyranometer — instrument to measure Albedo
  • 44% of Energy emitted by Visible Light (EMR)
  • Langley — unit to measure solar constant
  • Astronomical effects (Milankovitch cycles): Eccentricity of earth’s orbit = 95,000 years; Axial tilt = 41,000 years; Wobble and shift of axis (precession) = 21,000 years.

Scattering

  • Lord Rayleigh — explained the phenomena = *“Rayleigh Scattering”
  • Peterson: “at altitude and thickness of sun rays”
  • Scattering factors at different latitudes:
    • 0° → 1; 30°N/S → 1.15; 60°N/S → 2.0; 80°N/S → 5.7; 90° → 44.7

Cloud Reflection

  • Overcast Cirrostratus: 44–50%
  • Cumulonimbus: 90%

Cloudiness vs. Radiation

Cloudiness (0–10 scale) 0 1–3 4–7 8–9 10 (Clx)
Radiation (%) 100 93 82 68 41
  • Sunspots — dark areas of high temperature (faculae) on the sun’s surface

Heat Budget

*“Balance between incoming and outgoing radiation”

  • Albedo (Latin: Albus = white) = Earth’s reflectivity = 35% (Möller)
  • Two billion part of solar radiation = 1/2 billion of total energy
  • 38° N/S — after this latitude, outgoing radiation > incoming
  • Ocean currents transfer excessive heat from tropical to mid-latitude (30–50°) regions

Heat Budget by Different Scholars

Scholar Breakdown
George Kimball 42% albedo + 11% absorbed by water + 4% gases + 57% reach atmosphere
Möller 35% albedo (2% surface, 6% atmosphere, 27% clouds); 65% to heating atmosphere (14% atmosphere + 51% Earth surface)
Howard J. Critchfield R = Qs(1−α) + I; 51% reach Earth surface + 49% scattered (26% clouds, 4% Earth surface, 16% air/dust, 4% clouds)
Glenn T. Trewartha 50% reach surface + 20% absorbed atmosphere + 30% scattered by Earth surface
Strahler & Strahler 32% albedo (5% scattered atmosphere, 21% cloud, 6% Earth surface); 68% absorbed
W.H. Diner 15% absorbed at top of atmosphere + 40% reflected by clouds + 45% reach surface

Distribution of Temperature

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  • Isotherms — imaginary lines joining equal temperature
  • Temperature Anomaly — difference between mean temperature and parallel temperature

Climatic Zones

Zone Latitude Features
Tropical / Torrid 23½°N to 23½°S No winter season
Temperate 23½°N/S to 66½°N/S Both summer and winter
Frigid 66½°N/S to 90°N/S —
Minimum Temperature Range — The range of temperatures ever recorded had been the minimum in the continent of Antarctica.

Vertical Temperature

  • Normal / Environmental Lapse Rate = 0.0065°C/m (or 6.4 to 6.5°C/km).
  • Temperature at upper troposphere = −55°C to −60°C
  • Temperature varies at different times of the day because radiation intensity per unit area and the amount of reflection depend on the angle between solar rays and a tangent to the earth’s surface.
  • Mesosphere upper limit = −80°C
  • At 400 km = 1000°C

Temperature Inversion

Conditions Required

  • Long Nights
  • Clear Sky
  • Stable Weather
  • Dry Air

Types of Temperature Inversion

Type Description Region
Radiation Inversion Air near land cools fast during nights (midnight to 4 AM) Snow-covered North America, Europe
Air Drainage Inversion During long winter nights; houses on upper slopes are warmer Mountainous Europe, Brazil, Canada, Himalayas, USA
Advection Inversion Between air masses (cold & warm) Gulf of Mexico
Subsidence Inversion Concentration of pollutants in lower troposphere —
Convection Inversion Cumulonimbus clouds form —
Frontal Inversion Convergence of warm and cold air masses —
Trade Wind Inversion — —
Blocking Anticyclone Associated with NW Europe in both winter and summer. It causes prolonged cold dry seasons in Western Europe and exceptionally fine weather in summer. NW Europe

Atmospheric Pressure, General Circulation and Planetary Winds

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Distribution of Pressure

  • Lucian Vidie (1843) — invented the Aneroid Barometer
  • Isobar — imaginary line joining equal atmospheric pressure
  • Sea level pressure = 1013.25 mb

Factors Affecting Pressure

  • Temperature, Water Vapour, Rotation of Earth, Altitude, Gravitational Pull

Vertical Distribution

  • 34 millibars per 300 meters of ascent
  • 500 mb at 5.5 km height; 100 mb at 17 km height

Horizontal Distribution (Pressure Belts)

Belt Latitude Type
Equatorial Low 5°–5° North and South Low Pressure (Doldrums)
Sub-Tropical High 25°–35° North and South High Pressure (Horse Latitudes)
Sub-Polar Low 60°–65° North and South Low Pressure
Polar High 85°–90° North and South High Pressure
  • Doldrums — extremely calm air movement (Equatorial region)
  • Horse Latitude — Sub-tropical high pressure zone
  • Aleutian Low — Sub-polar low in the Pacific

General Circulation of Winds

  • Hadley Cell — Edmund Hadley (1686), modified by George Hadley (1735)
  • Pressure Gradient — change of pressure per unit distance
  • Coriolis Force — G.G. de Coriolis (1835)
    • Right deflection in Northern Hemisphere; Left in Southern Hemisphere
  • Geostrophic Balance: Maintained with the exact balance of the Coriolis force and the horizontal pressure gradient force. Geostrophic Wind is originated when the pressure gradient force is balanced by the Coriolis force acting in the opposite direction.
  • Geostrophic Thermal Wind: The speed of geostrophic thermal wind increases with height because each isobaric surface slopes more steeply than the one below it.
  • 1855 — W. Ferrel → Ferrel’s Law / **Buys Ballot’s Law*
  • Buys Ballot (1857): ‘0’ at Equator → Maximum at Poles; 30° lat = 50% deflection; 60° lat = 86.7% deflection

Tricellular Theory

Cell Latitude Named After
Hadley Cell 0°–30° N/S Edmund Haley (1686) → George Hadley (1735)
Ferrel Cell 30°–60° N/S William Ferrel
Polar Cell 60°–90° N/S —
  • Eddy Theory — circulation as a result of eddies

Planetary Winds

Trade Winds (30° N/S)

  • Speed: 15–25 km/h
  • Flow from sub-tropical high → equatorial low
  • Easterlies: NH → NE Trade; SH → SE Trade

ITCZ (Inter-Tropical Convergence Zone)

  • Also called **Equatorial Trough*

Westerlies

  • From sub-tropical high → sub-polar low
  • Cause rainfall on western margins of continents
  • NH → SW to NE; SH → NW to SE
  • Roaring Forties = 40°S; Furious Fifties = 50°S; Shrieking Sixties = 60°S
  • Dish-pan experiment relates to the formation of Rossby Waves embedded in the Westerlies.
  • Global Rainfall Changes: Rainfall distribution at a global-scale in recent decades is altered due to the alteration of the Hadley cell of general wind circulation.

Polar Winds

  • From Polar High → Sub-Polar Low

Monsoons and Jet Streams

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Monsoon

  • ‘Mausin’ (Arabic) / ‘Mansin’ (Malayan) = **Season*

Theories of Monsoon Origin

Theory Scholar Year
Classical Theory (thermal contrast between continents & ocean) Edmund Halley 1686
Air Mass Theory — —
Seasonal Shift of ITCZ H. Flohn —
Jet Stream Theory — —
Upper Air Circulation Theory M.T. Yin 1949
The Monsoon (book) Pierre Pedelaborde 1963
Tibetan Plateau influence P. Koteswaram 1952

Historical References

  • Rig Veda — first mention of monsoon
  • Al-Masudi — documented monsoon
  • Sidi Ali — 1564 AD
  • Indian Ocean Dipole (IOD): Refers to the Sea surface temperature anomaly and affects the Rainfall of countries that surround the Indian Ocean Basin.
  • Monsoon Delay Factors: Delay in monsoon onset in India is often caused by (1) El Niño, (2) Weak Tibetan anticyclone, (3) Presence of Westerly Jet Stream south of the Himalaya during summer, and (4) Late shifting of ITCZ.
  • Major Monsoon Factors: The major factors responsible for the monsoon type of climate in India include Location, Thermal contrast, Upper air circulation, and the Inter-tropical convergence zone.
  • Rainiest Month: According to the IMD, July is the rainiest month in India. The South-West Monsoon usually covers the whole country by the middle of July.

Monsoon Research Programmes

Programme Full Form Year
ISMEX Indo-Soviet Monsoon Experiment 1973–74
Monsoon 77 — 1977
MONEX Monsoonal Experiment 1979 (104 aircraft missions)
GARP Global Atmospheric Research Programme —
ICSU International Council of Scientific Unions —
IMMC International Monex Management Centres, Kuala Lumpur —

Jet Stream

  • Narrow band of strong wind blowing west to east in the upper troposphere
  • Speed: 150–430 km/h
  • Depth: 900–2150 meters
  • Seasonal shift in position

Types of Jet Streams

Type Latitude / Level Discovery
Circumpolar / Polar Front Jet Stream 40°–60° N/S; 300 mb pressure Bjerknes (1933); World War II; strongest in winter
Sub-Tropical Westerly Jet Stream 30°–35° N/S; 9100 m to 31,700 m —
Tropical Easterly Jet Stream Over India and Africa —
Subtropical-Subpolar Jet Stream Above 30 km —
Polar Night Jet Stream — Due to steep pressure & temperature gradient
Local / Regional Jet — Due to thermal and dynamic changes

Rossby Waves

  • Discovered by **C.J. Rossby in 1937*
  • **Index Cycle:*
    1. High Zonal Index
    2. Jet stream transforms into wavy path
    3. Shifts towards equator
    4. Low Zonal Index

Air Masses and Fronts

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Air Mass

  • A massive and thick, horizontally homogeneous air body with regard to temperature and humidity

Source Regions & Types

Code Source Region Type
cP Continental Polar Cold, Dry
mP Maritime Polar Cold, Moist
cT Continental Tropical Hot, Dry
mT Maritime Tropical Warm, Moist
mE Maritime Equatorial Warm, Very Moist
— Arctic and Antarctic Region Cold Air Mass

Thermodynamic Modification

  • Air mass heated from below → K (Kalt — cold air mass)
  • Air mass cooled from below → W (Warm air mass)

Fronts

Concept given by **Vilhelm Bjerknes & Jakob Bjerknes*

  • Frontogenesis — process of front formation
  • Inclined at surface: angle 1/30 to 1/200
  • Depth: 3000–5000 m; Width: 50–80 km; Movement: 50–80 km/h

Warm Front

  • Light warm air becomes aggressive and **rises slowly over cold dense air*
  • Slope: 1:100 to 1:400
  • Clouds: Cirrus (Ci) → Cirrostratus (Cs) → Altocumulus (Ac) → Altostratus (As)

Katafront

  • In Katafronts, the warm airmass sinks relative to the cold airmass. They are less active, and warm air is overrun by dry descending air.

Cold Front

  • Cold air becomes aggressive and invades the warm air; forcibly lifts warm air
  • Slope: 1:50 to 1:100
  • Dry climate conditions

Occluded Front

  • When a cold front overtakes a warm front and lifts the warm air mass completely off the ground.
  • Warm Occluded Front: The air behind the cold front is warmer than the cool air it is overtaking.

Quasi-Stationary Front

  • Front becomes almost stationary

Stationary Front

  • No forward motion along the line of transition between two air masses

Cyclones — Temperate and Tropical

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Temperate Cyclone

  • Also called **Extratropical Cyclones / Wave Cyclone*
  • Latitude: 35°–65° N/S
  • Shape and Size: Radius — 400 to 800 km
  • Wind velocity: 40–60 km/h
  • Moves **west to east*

Theories of Origin

Theory Scholar Year
Due to convergence of two opposing air masses Fitzroy 1863
Dynamic Theory Shaw and Lempfert 1911
Eddy Theory — —
Bergen Theory / Wave Theory / Frontal Theory V. Bjerknes & J. Bjerknes (Norway) 1918

Stages of Temperate Cyclone (Bergen Theory)

  1. Incipient Stage
  2. Juvenile Stage
  3. Early Maturity
  4. Full Maturity
  5. Old Stage
  6. End Stage

Weather Regions

  • North Atlantic Ocean
  • Mediterranean Sea
  • North Pacific Region
  • China Sea

Tropical Cyclone

  • Diameter: 80–300 km (some 50 km or less)
  • High wind speed; sea temperature must be **27°C or more*
  • They mostly occur in late summer and autumn. They do not occur beneath the jet stream.
  • No cyclones occur along the equator because the Coriolis force is zero.
  • Eye of the cyclone — centre of extreme low pressure in spite of descending wind. At the eye, adiabatic warming of descending airmass accentuates high temperature. Note that some cyclones may not develop an eye.

Classification (Christopherson, 1995)

Type Wind Speed
Tropical Disturbance Low wind speed; 5°N–20°N; >34 knots
Tropical Depression Up to 60 km/h (34 knots)
Tropical Storm 63–118 km/h

Hurricanes / Typhoons

  • Region: Caribbean Sea & Gulf of Mexico; 8°–15° N/S
  • Diameter: 150–500 km
  • Pressure: 950 mb
  • Wind speed: 120–200 km/h
  • Eye = 8–50 km
  • **Saffir-Simpson Hurricane Damage Scale (1–5)*

Tornadoes (Twisters)

  • In USA; associated with thunderstorms
  • Diameter: 100 metres
  • Pressure at centre: 10 mb
  • Wind speed: 400 km/h
  • Dry Line — in Mexico, zone of great turbulence
  • Fujita Scale (F-scale) — T. Theodore Fujita, University of Chicago
  • Mamma clouds — formed at the base of severe thunderstorms
  • News clouds — appear like a long rolling cylinder / wedge
  • Doppler Radar: Used for Nowcasting (very short-range weather forecasting).
  • Water spout: An intense low pressure system similar to a tornado but develops over a sea or large water-body; typically associated with a cumulonimbus cloud-base.

Structure of Tropical Cyclone

Layer Description
The Eye Central part — calm, extreme low pressure
Eye Wall Ring of intense convection
Spiral Bands Bands of rain
Annular Zone —
Outer Convective Band Trade wind cumulus
Lower Layer Inflow layer
Middle Layer —
Upper Layer Outflow layer

Precipitation: Types and Distribution

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Types of Precipitation

Type Description
Snowfall Temperature below freezing point
Sleet Frozen raindrops and re-frozen melted snow water
Hail Hard rounded pellets; diameter 5 mm to 5 cm; formed by supercooled water or ascending air currents
Drizzle Spray-like rainfall; small water drops; fine drizzle = ‘mist’ (North America)
Rainfall Cloud particles; humid air rises, cools, condensation → precipitation
  • Fog: Geographically, the most extensive fogs in India during winter are mainly Radiation fogs.

Measurement of Humidity

  • Specific Humidity: The ratio of the weight of water vapour in a parcel of the atmosphere to the total weight of moist air.
  • Relative Humidity (RH): \(\frac{\text{Actual water vapour content}}{\text{Water vapour capacity (saturation)}} \times 100\). (e.g., at 25°C, if capacity is 20g and content is 15g, \(RH = (15/20) \times 100 = 75\%\)).
  • Lithium chloride-based hygrometer: A technique for measuring atmospheric moisture based on electrical resistance.

Dew Formation

Favourable conditions for the formation of dew include: 1. **Clear sky.* 2. Calm evening without turbulence in the atmosphere. 3. Nocturnal radiative cooling below the dew point temperature of the air resting near the earth’s surface. 4. Warm previous day to raise the moisture content of the air.

Rainfall Formation Processes

Process Scholars Year
Bergeron–Findeisen Process (Ice Crystal Process) Tor Bergeron and von Findeisen. It involves mixed clouds with co-existence of ice and water, differences in saturation vapour pressure, and migration of water vapour towards sublimation nuclei. 1933
Collision–Coalescence Process George Simpson and Mason; modified by Langmuir —

Key Definitions

  • Cloudburst: Defined by the IMD as rainfall of \(\ge\) 10 cm / hour.

Types of Rainfall

  • **Convectional Rainfall*
  • Orographic Rainfall (Rain Shadow on lee side)
  • **Cyclonic / Frontal Rainfall*

Rainfall Distribution Classes

Class Amount
Heavy 250 cm+
Moderate 1000–2000 mm
Inadequate 500–1000 mm
Low 250–500 mm
Extremely Low Below 250 mm

Classification of World Climates

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Koeppen’s Climate Classification

  • Dr. Wladimir Koeppen — University of Graz
  • Empirical Classification based on:
    • Annual and monthly means of temperature
    • Annual and monthly means of precipitation
    • Based on **five vegetation zones*

Timeline of Revisions

Year Work
1931 Grundriss und Klimakunde — world map of climatic classification
1936 Koeppen–Geiger: Handbuch der Klimatologie (Vol. I–V)
1953 Koeppen–Geiger–Pohl’s model

Major Climate Groups

Symbol Climate Type Definition
A Tropical Rainy (Megathermal) Average temperature above 18°C
B Dry Climates Defined by precipitation-to-evaporation ratios
C Mid-Humid (Mesothermal) Coldest month: −3°C to 18°C; one month avg. >10°C
D Snowy Forest (Microthermal) / Boreal Coldest month below −3°C; warmest month >10°C
E Polar Avg. temperature of warmest month below 10°C

A, C, D, E → defined by temperature; B → defined by precipitation-to-evaporation ratios

Sub-Types (Second Letter)

Letter Meaning
f No dry season; minimum precipitation 6 cm every month
w Dry season in winter
s Well-defined summer dry season
m Monsoon — rainforest despite short dry season

Third Letter (Temperature)

Letter Meaning
a Hot summer (+22°C)
b Cool summer (max 22°C)
c Short cool summer (10°C)
x Rainfall in late spring

B (Dry) Subdivisions

Symbol Meaning
h (heiss) Hot
k (kalt) Cold
n (Nebel) Frequent fog
w Winter drought
s Summer drought
BW ‘Wüste’ — desert arid climate (<40 cm)
BS ‘Steppe’ — dry grassland semi-arid
BWh Tropical desert (+18°C)
BWk Middle latitude cold desert
BSh Tropical steppe
BSk Mid-latitude cold steppe
BWn / BSn Along littorals with cool ocean currents

Detailed Climate Codes

Code Climate
Af Rainforest / Tropical Wet; driest month ≥ 6 cm
Aw Savanna — Tropical Wet and Dry
Am Monsoon Climate
Cf Precipitation throughout the year
Cw Dry winter
Cs Dry summer
Df Cold climate, humid winter, no dry season
Dfc Long warm summer
Dfb Long cool summer
Dfc Subarctic, short cool summer
ET Tundra Climate
EF Perpetual Frost (Ice Cap)

Thornthwaite’s Climate Classification

  • **C.W. Thornthwaite*
  • 1931 — Applied to North America; 1933 — Whole world classification
  • 1948 — Modified scheme
  • Complex and empirical in nature

1931 Scheme

Precipitation Effectiveness (P/E Index)
Symbol Climate P/E Index
A Wet — Rainforest 128 and above
B Humid — Forest 64–127
C Sub-Humid — Grassland 32–63
D Semi-Arid — Steppe 16–31
E Arid — Desert Below 16
Small Letter Suffixes
Letter Meaning
r Adequate rainfall in all seasons
s Rainfall deficient in summer
w Rainfall deficient in winter
d Rainfall deficient in all seasons
Thermal Efficiency (T/E Index)
Symbol Climate T/E Index
A’ Tropical Above 128
B’ Mesothermal 64–127
C’ Microthermal 32–63
D’ Taiga 16–31
E’ Tundra 1–15
F’ Frost 0

Thornthwaite gave **32 types of climates*

1948 Revised Scheme

  • Precipitation Effectiveness
  • Seasonal Distribution of Rainfall
  • Thermal Efficiency
  • Moisture Index (Im) — key addition

Criticisms of Thornthwaite’s Classification

  • Limited climatic variables: It largely ignores the role of prevailing winds, air pressure, and air masses.
  • Complexity and Replicability: It uses complex indices, making it difficult to replicate for other areas.
  • Overemphasis on Water Balance: This rigid mathematical approach may not accurately capture true, holistic climate variability.

Köppen Symbol Matching

  • Tropical Monsoon: Am
  • Mediterranean: Csa / Csb
  • Tropical Hot Desert: Bwh
  • Arctic: ET / EF

Major Classification Systems Summary

Classifier Basis Approach
Koeppen (1931) Temperature + precipitation + vegetation Empirical
Thornthwaite (1931, 1948) P/E index, T/E index, Moisture Index Empirical
Trewartha Modified Koeppen Empirical
Flohn Atmospheric circulation Generic / Dynamic
Strahler Solar radiation + wind belts Dynamic

Oceanography

Origin of Ocean Basins

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NoteKey Concepts
  • Continental Drift and Seafloor Spreading: Wegener’s theory and Hess’s seafloor spreading hypothesis explain ocean basin formation.
  • Plate Tectonics: Ocean basins form at divergent boundaries (mid-ocean ridges) and are consumed at convergent boundaries (subduction zones).
  • Wilson Cycle: Complete lifecycle of ocean basins — embryonic (rift valley), juvenile (Red Sea), mature (Atlantic), declining (Pacific), terminal (Mediterranean), suture (Himalayas).
  • Age of Ocean Floor: Youngest at mid-ocean ridges, oldest near continental margins — confirmed by magnetic anomalies.
  • Passive vs. Active Continental Margins: Atlantic-type (stable, wide shelves) vs. Pacific-type (subduction, narrow shelves, trenches).

Origin of Ocean Basins — Detailed (NET Notes — Pulakesh Pradhan)

Hypotheses

Hypothesis Year Scholar
Nebular Hypothesis 1755 Immanuel Kant; La Place
Planetesimal Hypothesis 1904 T.C. Chamberlain (geologist, USA)
Tetrahedral Hypothesis 1873/1875 Lowthian Green
Continental Drift (first proposed) 1910 F.B. Taylor
Drift Hypothesis 1911 H.B. Baker
Displacement Hypothesis 1912 Alfred Wegener
  • Carboniferous (298–358 Ma) — Pangaea started to break

Hemisphere Distribution of Water

Hemisphere Area under Water Share of Ocean Water
Northern 60.7% 43%
Southern 80.9% 57%

Depth of the Ocean (NET Notes)

  • Sonic Sounding Method — geographical method to measure depth
  • Fathoms — unit to measure ocean depth (1 fathom = 2 metres)
  • Hypsographic Curve: Kossinna (1921) first used; Sverdrup (1942) modified

Ocean Floor Zones

Zone Depth Key Statistics
Continental Shelf Up to 200 m 7.6% of sea area; Atlantic 13.3%, Pacific 5.7%, Indian 4.2%
Continental Slope 200–2000 m 8.5% of total ocean area; Avg. slope 4°17’ (Shepard)
Deep Sea Plain 2000–6000 m 82.7% of total bottom
Deeps (Trenches) Below 6000 m 1.2% of sea bottom; 57 total (Pacific 32, Atlantic 19, Indian 6)

Challenger Expedition (1872–76)

  • By Royal Society of London, vessel **HMS Challenger*
  • Prompted by **Charles Wyville Thomson*
  • Ocean deposits study by **Sir John Murray & Prof. Alphonse Renard*

Submarine Canyons (NET Notes)

  • Deep gorges on the ocean floor — restricted to continental shelf, slope, rise
  • Formed due to turbidity currents; also river origin and tectonic movement

Bottom Relief of the Oceans

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NoteKey Concepts
  • Continental Shelf: Shallow, gently sloping extension of continental landmass — up to 200m depth. Rich in marine resources.
  • Continental Slope: Steep descent from shelf edge to deep ocean floor. Submarine canyons.
  • Continental Rise: Gentle slope at base of continental slope — sediment accumulation from turbidity currents.
  • Abyssal Plains: Extensive flat areas of deep ocean floor — covered with fine sediments. Pelagic oozes cover about 50% of the world ocean floor area.
  • Mid-Ocean Ridges: Underwater mountain chains at divergent boundaries — Mid-Atlantic Ridge, East Pacific Rise, Indian Ocean Ridge system.
    • Slow-spreading ridges are characterised by an axial graben with 1500–3000 m depth, faulted topography, and intermittent shield volcanoes.
    • Ninety East Ridge (Indian Ocean): Formed by the Kerguelen Hotspot through the eruption of ocean island basalt. This hotspot is also linked to the formation of the Rajmahal Hills in India.
    • Fracture Zones: Elevation differences across ocean floor fracture zones are explained by Age, Temperature, and Density differences (not material differences).
  • Deep Sea Trenches: Deepest parts of ocean — Mariana Trench (11,034m), Tonga Trench, Java Trench. Formed at subduction zones, they trace boundaries between tectonic plates, are almost parallel to the ‘Ring of Fire’, and are characterized by earthquakes. Deepest parts do not always lie away from the coast, as they are often near active continental margins.
    • Submarine Canyons: e.g., Swatch of No Ground, extending offshore from the Ganga river delta. Pelagic oozes are quite uncommon in their occurrences within submarine canyons.
  • Isobath: A line connecting equal depths below a water surface.
  • Seamounts and Guyots: Submarine volcanic mountains — guyots are flat-topped (eroded by waves).
  • Calcareous Oozes: Found in lower latitudes and up to a depth of 4500 m because organisms with carbonate shells predominate in warm, shallow water, and calcium carbonate dissolves very slowly below this depth (Carbonate Compensation Depth).
  • Specific Ocean Features: Atlantic (S-shaped ridge), Pacific (Ring of Fire, trenches), Indian (triple junction, Ninety East Ridge).
    • Marginal Sea: The Andaman Sea is considered a marginal sea, in true sense, in the Indian Ocean.

Bottom Relief — Atlantic Ocean (NET Notes — Pulakesh Pradhan)

  • Area: 82 million sq. km (S-shape); **1/6 of total world area*
  • 25.7% area less than 2000 m depth

Continental Shelf

  • Newfoundland–British Islands → World’s widest continental shelf
  • Grand Bank, Dogger Bank, Bay of Biscay

Mid-Atlantic Ridge

  • ‘Meteor’ — German Oceanographic Vessel (1920)
  • Pico Island of Azores → highest peak; Rocks of St. Paul → sharpest peak
  • Features: Telegraph Plateau, Dolphin Rise, Romanche Deep, Challenger Rise

Basins of the Atlantic Ocean (11 basins)

Basin Notes
Labrador Basin Between Greenland & Newfoundland
North-Western Atlantic Basin Biggest
Brazilian Basin ~6000 m depth
North-East Atlantic (Iberian) Basin ~5000 m avg depth
Cape Verde, Guinea, Cape, Argentina, Agulhas Basins Various locations

Bottom Relief — Indian Ocean (NET Notes)

  • Average Depth: 4000 m; 58.8% between 4000–6000 m
  • Continental Shelf: Bay of Bengal & Arabian Sea; width 400 miles
  • Andaman & Nicobar Islands — submerged folded mountain (Burma)
  • Laccadives, Maldives — submarine ridge location

Continental Ridges

  • Laccadive–Chagos Ridge, Chagos–Saint Paul Ridge, Kerguelen–Gaussberg Ridge, Seychelles–Mauritius Ridge

Basins (10): Oman, Arabian, Somali, Mauritius, Natal, Agulhas, Atlantic–Indian–Antarctic, Andaman, Cocos–Keeling, Eastern Indian–Antarctica

Bottom Relief — Pacific Ocean (NET Notes)

  • 1/3 of total Earth area; E–W: 10,000 miles; N–S: 9,300 miles
  • Average Depth: 5000 m

Island Groups

Group Islands
Melanesia Solomons, New Hebrides, Fiji
Micronesia Marshalls, Carolines, Gilbert Ellice
Polynesia Society, Cook, Tuamotu
Volcanic Hawaiian Islands
Coral Fiji, Funafuti, Ellice

Ridges

  • Albatross Plateau / East-Pacific Ridge, Cocos Ridge, Hawaiian Swell, Marcus–Necker Rise, Tasmania Ridge

Major Deeps/Trenches (Pacific — 32 recorded)

Trench Depth
Mariana / Challenger Deep 11,034 m (deepest)
Tonga / Aldrich Deep 10,882 m
Kuril–Kamchatka Deep 10,542 m
Philippine / Swire Deep 10,497 m
Kermadec Trench 10,047 m
Japan Trench 9,000 m
Aleutian Trench 7,679 m

Temperature, Salinity, and Density of Oceans

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NoteKey Concepts
  • Ocean Temperature: Decreases with depth — three layers: mixed layer, thermocline, deep water. Average surface temperature ~17°C. Coasts are relatively warmer near onshore wind, but colder where wind blows from land towards sea because wind from land drives warm surface water away, causing cold bottom water to upwell.
  • Factors Affecting Temperature: Latitude, ocean currents, depth, season, proximity to landmass.
  • Salinity: Average 35‰ (parts per thousand). Highest in subtropics (high evaporation), lowest near equator and poles. Sea water is saline primarily because of the solution of salts derived from ocean floor rocks.
    • Forchammer’s Principle (Rule of constant proportion): The ratio of major salts is constant. For example, Potassium constitutes 1.1% of dissolved salt in seawater.
  • Factors Affecting Salinity: Evaporation, precipitation, river discharge, ice formation/melting, ocean currents.
  • Density of Seawater: Function of temperature, salinity, and pressure. Cold, saline water is densest. Density does not decrease with decreasing depth (it decreases with increasing temperature and decreasing salinity).
    • Pycnocline: A zone below the surface waters and above the deep waters where density changes rapidly. It is heavily influenced by the thermocline (temperature) and can also act as a halocline (salinity). Potential density of seawater is primarily dependent on Salinity and Temperature.
  • Thermohaline Circulation: Global conveyor belt driven primarily by differences in Heat and Density.
  • CaCO₃ Compensation Depth (CCD): The depth in the ocean below which the rate of supply of calcium carbonate lags behind the rate of solvation. It is related to the amount of carbonic acid present in sea water and generally occurs at depths greater than 2,000 m.
  • Heat and Salt Budget: Ocean as a heat reservoir — role in climate regulation.
  • Desalination Processes: Common methods include Reverse osmosis, Electrolysis, and Freeze separation.

Temperature of Oceans — Detailed (NET Notes — Pulakesh Pradhan)

  • M.F. Maury — Founder of ‘Scientific Marine Meteorology’
  • Pettersson–Nansen water bottle — for water sampling
  • Pyrheliometer — measurement of solar insolation

Processes of Heat Transfer

  1. Convection, 2. Absorption, 3. Kinetic energy → heat, 4. Chemical processes, 5. Condensation of water vapour

Insolation at Different Latitudes (Blair)

Latitude Insolation
Equator (0°) 100%
33°N/S 88%
50°N/S 68%
70° 47%
Poles 12%

Vertical Temperature Distribution

Depth Temperature
100 fathoms 60.7°F
500 fathoms 40.1°F
1000 fathoms 36.5°F
2200 fathoms 35.2°F

Salinity of Oceans — Detailed (NET Notes)

  • Varies from **34 to 37.5‰*
  • Methods: Titration (constancy of composition), Hydrometer (sample)

Chemical Composition (Dittmar, 1884 — Challenger Expedition)

Salt Amount (‰) Percentage
Sodium Chloride 27.2 77.8%
Magnesium Chloride 3.80 10.9%
Magnesium Sulphate 1.65 4.7%
Calcium Sulphate 1.2 3.6%
Potassium Sulphate 0.86 2.5%

Controls of Salinity

  • Evaporation, Precipitation, River water, Atmospheric pressure, Movement of sea water, Periodic variation

Salinity by Ocean / Sea

Ocean / Sea Salinity (‰)
Red Sea 37–41 (highest)
Mediterranean Sea 37–39
Atlantic Ocean 35.67
Baltic Sea 3–15 (lowest)
Hudson Bay 3–15

Density of Sea Water — Detailed (NET Notes)

  • Pure water has maximum density at **4°C*

Controlling Factors

Factor Details
Temperature Varies from −2°C to 30°C
Salinity Average density at 35‰ = 1.028
Atmospheric Pressure Measured in decibars
  • Holland–Hansen — T–S Diagram to delineate water masses

Water Masses

Water Mass Type
Equatorial Water Mass Surface
Antarctic Circumpolar Surface
Sub-Antarctic / Sub-Arctic Intermediate
Central Water Mass Due to sub-tropical convergence
Antarctic Bottom Water Bottom
North Atlantic Deep Bottom Water Deep

Waves, Tides, and Ocean Currents

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NoteKey Concepts
  • Ocean Waves: Generated by wind — wave height, wavelength, period, fetch. Constructive vs. destructive waves. Water waves are termed ‘shallow’ when the water depth is less than 1/20th of the wavelength.
    • Wave Transformation at Coast: As a wave approaches the coastline, wave height increases, celerity (speed) decreases, and wave length decreases.
    • Wave Base: The depth where circular orbital motion of water molecules declines to zero, which is equivalent to 1/2 of the wavelength.
    • Translatory Waves: Develop in the land-ward side after wave breaking.
    • Breaker Types: Waves break as they approach the coast because water is pulled down by gravity as wave steepness exceeds a critical value.
      • Spilling Breaker: Gentle beach gradient, fine grain size, high energy dissipation.
      • Plunging Breaker: Steep beach gradient, coarse grain size, high energy dissipation.
      • Surging Breaker: Steep beach gradient, moderate grain size, moderate/low energy dissipation.
  • Tides: Periodic rise and fall of sea level caused by gravitational pull of Moon and Sun. Development of the earth’s tidal bulge on the opposite direction of the moon is best explained by Centrifugal force.
    • Spring tides (syzygy), neap tides (quadrature)
    • Perigean Spring Tides: These tides have the highest amplitude among various tidal types, occurring when the moon is at perigee (closest to Earth) during a full or new moon.
    • Diurnal, semi-diurnal, and mixed tidal patterns
    • Rotating Tide: The co-tidal line rotates in a clockwise direction, and tidal amplitude increases away from the amphidromic point, which is a position inside the ocean that experiences no fluctuation of water level due to tide.
    • Tidal bore and tidal range
  • Ocean Currents: Large-scale movement of seawater driven by wind, temperature, salinity, and Coriolis force.
    • Warm Currents: Gulf Stream, Kuroshio, North Atlantic Drift, Brazil Current
    • Cold Currents: Labrador, Benguela, Peru (Humboldt), California Current, Kamchatka Current
    • Gyres: Circular current systems in major ocean basins — North Atlantic, South Pacific, etc.
    • Ekman Transport: In the southern hemisphere, it occurs 90° to the left of the wind direction.
  • Upwelling and Downwelling: Vertical water movements — upwelling brings nutrients to surface (productive fishing grounds).
  • **Coastal Circulation and Hazards:*
    • Tsunami: Involves movement of water from surface to sea-floor. The shoaling effect can greatly increase wave-heights closer to the coast.
    • Rip-cell circulations: Developed along the coasts by the combination of shore-normal and long-shore currents.

Tides & Tidal Waves — Detailed (NET Notes — Pulakesh Pradhan)

  • Pliny — tides developed due to combined action of sun and moon
  • Isaac Newton (1687) — first rational explanation: Gravitational attraction
  • Ratio of tidal forces: Moon : Sun = **11 : 5*

Key Tidal Concepts

Term Description
Syzygy Sun–Moon–Earth in line → Spring Tides
Quadrature Moon at right angle → Neap Tides
Perigee Moon nearest to Earth → tides 20% above average
Apogee Moon farthest → tides 20% below average

Types of Tides

Type Interval
Semi-diurnal 12½ hours — two high, two low per day
Diurnal 24¾ hours — one high, one low per day
Spring Tides Once a fortnight (syzygy)
Neap Tides Once a fortnight (quadrature)

Theories of Tides

Theory Scholar Year
Equilibrium Theory Isaac Newton 1687
Progressive Wave Theory William Whewell 1833
Dynamical Theory Laplace 1755
Stationary Wave Theory Dr. R.A. Harris —

Ocean Currents — Detailed (NET Notes)

  • Alexander Von Humboldt (1816) — identified controls of ocean currents

Pacific Ocean Currents

Current Type
Kuroshio / Japan Current Warm
Peruvian (Humboldt) Current Cold
California Current Cold
Oyashio / Kuril Current Cold
East Australian Current Warm

Indian Ocean Currents

Current Type
Monsoon Current Warm
Mozambique & Agulhas Current Warm
West Australian Current Cold

Atlantic Ocean Currents

Current Type
Gulf Stream Warm
Brazil Current Warm
Labrador Current Cold
Benguela Current Cold

Sea-Level Changes

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NoteKey Concepts
  • Eustatic Changes: Global sea-level changes due to change in ocean water volume.
    • Glacial periods → sea-level fall (water locked in ice sheets)
    • Interglacial periods → sea-level rise (ice melting)
  • Isostatic Changes: Local changes due to crustal uplift or subsidence.
    • Post-glacial rebound (Scandinavia, Canada). Some European coasts record sea-level fall due to isostatic rebound resulting from deglaciation.
    • Tectonic subsidence
  • Current Sea-Level Rise: The average global rate of sea-level rise at present is about 3.3 mm/year. Past records of sea-level changes are best deciphered from Mangrove-fringed coasts.
  • Carbonate Compensation Depth (CCD): The depth in the ocean below which the rate of supply of calcium carbonate is exceeded by the rate of dissolution. In most oceans, the CCD is usually about 4,500 meters.
  • Impacts: Coastal flooding, erosion, saltwater intrusion, loss of wetlands, island submergence.
  • Emergent and Submergent Coastlines: Raised beaches, marine terraces (emergent); rias, fjords, drowned valleys (submergent).
  • Coral Reefs as Indicators: Reef growth tracks sea-level changes — Darwin’s subsidence theory.
  • **Maritime Law:*
    • UNCLOS: Stands for United Nations Convention on the Law of the Sea.
    • EEZ (Exclusive Economic Zone): In order of decreasing area of EEZs, the sequence is USA > France > Australia > Russia.

Sea Level Changes — Detailed (NET Notes — Pulakesh Pradhan)

Types of Sea Level Change

Type Description
Eustatic Change caused by change in volume of water in ocean store
Isostatic Local change caused by change in level of land relative to sea
Emergence Impact of a relative fall in sea level
Submergence Impact of a rise in relative sea level

Causes of Sea Level Rise

Cause Rate
Thermal expansion 1.2–1.6 mm/yr
Glacial / ice cap melting 0.4 mm/yr (1961–1990); 1.0 mm/yr since 2001

Effects

  • Coastal flooding, storm surge, coastal erosion (70% of worldwide beaches being eroded)
  • Current average: 3 mm/yr sea level rise

Coral Reefs and Ocean Deposits

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NoteKey Concepts
  • Coral Reefs: Biogenic formations by coral polyps — require warm (>20°C), shallow, clear, saline water.
    • Fringing Reefs: Grow directly from shore — most common type
    • Barrier Reefs: Separated from shore by lagoon — Great Barrier Reef
    • Atolls: Ring-shaped reefs enclosing lagoon — formed by subsidence of volcanic island (Darwin’s theory)
  • Coral Bleaching: Expulsion of symbiotic algae due to stress (warming, pollution) — widespread global threat.
  • Ocean Deposits: Materials deposited on the ocean floor.
    • Terrigenous: Land-derived sediments (gravel, sand, silt, clay) — near coasts
    • Pelagic: Deep-sea deposits — biogenic oozes (foraminiferal/calcareous, radiolarian/siliceous), red clay
    • Authigenic: Formed in-situ — manganese nodules, phosphorite deposits

Ocean Deposits — Detailed (NET Notes — Pulakesh Pradhan)

  • 1773 — Captain Phipps: 683 fathoms; found blue mud
  • 1891 — Sir John Murray & Prof. Alphonse Renard: 1st world map of oceanic deposits

Classification by Source

**(A) Lithogenous / Terrigenous Material:* - Blue Mud — deeper ocean; 14.5 million sq. km - Red Mud — calcium carbonate 6–61%; off river mouths - Green Mud — glauconite; 100–900 fathoms

(B) Products of Volcanism: Sub-aerial and sub-marine

**(C) Organic Remains:* - Pelagic Calcareous: Pteropod Ooze, Globigerina Ooze - Pelagic Siliceous: Radiolarian Ooze, Diatom Ooze

(D) Inorganic Precipitates: Dolomite, iron, manganese oxide, phosphate

(E) Red Clay: Most widely spread pelagic deposit — hydrated silicate of aluminium

(F) Extra-Terrestrial: Meteoric dust, cosmic spherules

Coral Reefs — Detailed (NET Notes)

  • Masses of limestone and dolomite; confined between **25°N to 25°S*
  • Built by coral polyps; Zooxanthellae give colour
  • Western coast of continents — **no coral reefs*

Conditions for Growth

Condition Requirement
Temperature 68–70°F (20°C)
Depth Max 200–250 feet (60–70 m)
Water Sediment-free
Salinity 27‰ to 40‰

Types

Type Description Example
Fringing Reef Narrow belt along steep shores; boat channel South Florida Reef
Barrier Reef Largest type; 45° outward slope Great Barrier Reef (Australia)
Atoll Oval-shaped coral ring enclosing lagoon Funafuti Atoll

Theories of Coral Reef Formation

Theory Scholar Year
Subsidence Theory Charles Darwin 1837
Non-Subsidence / Stand Still Theory Murray 1880
Glacial Control Theory Daly —

Quick Reference

Physical Geography Quick Reference

Key Books and Authors

Book Author Year
Physical Geography Arthur N. Strahler 1951
Principles of Physical Geography F.J. Monkhouse 1954
Kosmos Alexander von Humboldt 1845
Physical Geography Savindra Singh -

Key Branches & Scope

  • Geomorphology: Study of landforms, their evolution and related processes. (Key figures: W.M. Davis, Walther Penck, L.C. King).
  • Climatology: Study of atmospheric conditions, weather systems, and climate types. (Key figures: Köppen, Thornthwaite, Trewartha).
  • Oceanography: Study of marine environments, ocean currents, tides, and ocean floor topography. (Key figure: Matthew Maury).
  • Biogeography: Study of the distribution of species and ecosystems in geographic space. (Key figure: Alfred Russel Wallace).

Fundamental Concepts

Concept Propounder Description
Uniformitarianism James Hutton “The present is the key to the past”
Isostasy C.E. Dutton State of gravitational equilibrium between Earth’s lithosphere and asthenosphere
Plate Tectonics Wilson, Morgan, Le Pichon Movement of lithospheric plates
Continental Drift Alfred Wegener (1912) Movement of continents over time (Pangaea, Panthalassa)

Notes compiled by Geography Team