LANDFORMS AND THEIR EVOLUTION

IMPORTANT NOTES

 Landform Definition:
→ Small to medium tracts or parcels of the earth’s surface.

 Landscape Definition:
→ A collection of related landforms forming a larger unit.

 Agents of Geomorphic Change:

→ Running water, groundwater, wind, glaciers, and waves perform erosion.
→ Deposition follows erosion and also reshapes landforms.

 Slow Evolution:
→ Most geomorphic processes act slowly, and changes take a long time.

 Dynamic Nature of Landforms:

→ Landforms continue to evolve in shape, size, and nature due to geomorphic agents.

 Climatic and Tectonic Influences:

→ Climatic variations and vertical/horizontal movements of landmasses can modify the intensity
or nature of geomorphic processes.

 Concept of Evolution:
→ Landform evolution = transformation of one form to another or changes within an existing
form over time.

 Stages of Landform Development:

→ Landforms go through Youth → Mature → Old Age, like living organisms.

🟦 1. Running Water

🔸 Erosional Landforms
🌊 Running Water as a Geomorphic Agent in Humid Regions

✅ 1. Importance

 In humid regions with heavy rainfall, running water is the most dominant agent of
erosion.
 Two components:
o Overland flow (sheet flow)

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 o Linear flow (streams and rivers)

✅ 2. Process of Erosion and Deposition

 Youthful rivers on steep gradients cause vigorous erosion (mainly vertical/down

cutting).
 With time, gradients reduce → erosion slows → deposition increases.
 Lateral erosion becomes more dominant than vertical erosion.
 Hills and valleys gradually reduce → eventually forming peneplains (almost flat plains
with occasional residual hills called monadnocks).

✅ 3. Sheet Erosion to Valley Formation

 Sheet erosion by overland flow → removal of material → forms rills.

 Rills deepen and widen → form gullies.
 Gullies unite → form valleys.
 Result: Network of valleys and eventual reduction of relief.

✅ 4. Evolutionary Stages of Fluvial Landscapes

🟡 Youth Stage

 Few streams, poor integration.

 Shallow V-shaped valleys.
 No or narrow floodplains.
 Broad, flat divides with swamps, marshes, and lakes.
 Waterfalls and rapids present.
 Initial meanders may entrench into uplands.

🟡 Mature Stage

 Well-integrated stream system.

 Deep V-shaped valleys.
 Broad trunk streams with wider floodplains.
 Inter-stream areas flatten.
 Waterfalls and rapids disappear.

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🔵 Old Stage

 Very few small tributaries.

 Gentle gradients, broad floodplains.
 Features like:
o Meanders
o Natural levees
o Oxbow lakes
 Divides are flat and broad.
 Entire landscape near or at sea level.

🟦 Key Concept: Peneplain

 Final stage of fluvial erosion.

 Almost level plain with minor relief.
 Leftover resistant features = Monadnocks.

🌊 EROSIONAL LANDFORMS OF RIVERS

1. Valleys

 Formation: Begin as rills → gullies → valleys.

 Types:
o V-shaped valleys: Common in youthful stages of
rivers.
o Gorge: Deep, narrow, with steep or vertical sides;
equal width at top and bottom; forms in hard rocks.
V SHAPPED VALLEYS

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 o Canyon: Deep, step-like side slopes; wider at the
top than bottom; common in horizontally bedded
sedimentary rocks.
o Note: Canyons are a variant of gorges.

2. Potholes and Plunge Pools

 Potholes: Circular depressions on rocky stream beds formed

by abrasion from pebbles and boulders.
 Plunge Pools: Large, deep potholes formed at the base of George
waterfalls due to force of falling water and swirling
boulders.

3. Incised or Entrenched Meanders

 Formation: Meanders cut deep into hard rock due to

vertical erosion.
 Occurrence: In rivers flowing over steep gradients with
minimal lateral erosion.
 Contrast: Normal meanders occur on gentle slopes Canyon
with more lateral erosion.

4. River Terraces

 Definition: Old valley floors or floodplain levels left

elevated due to river down-cutting.
 Types:
o Bedrock terraces (no alluvium).
o Alluvial terraces (with deposits).
 Cause: Vertical erosion into former floodplain.
 Paired terraces: Terraces on both sides of the river at Figure 1 Incised or Entrenched Meanders
the same elevation.

River Terraces

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 🌍 DEPOSITIONAL LANDFORMS OF RIVERS

1. Alluvial Fans:

 Formation: When fast-flowing streams from hills suddenly enter gentle foot slope
plains, they lose velocity and deposit coarse material.
 Shape: Cone-shaped deposit (low or steep cone).

 Climate Influence:
o Humid areas → Low cone, gentle slope.
o Arid/Semi-arid areas → High cone, steep slope.
 Distributaries: Streams shift across the fan,
forming distributary channels.

2. Deltas

 Formation: At the river mouth where it meets a standing body of water (like a sea).
 Process: River loses energy and deposits sediments.
 Structure:
o Well sorted, stratified deposits (coarse near land, fine towards sea).
 Growth: Distributaries increase in length as delta expands.
 Comparison:
o Like alluvial fans, but formed at river mouths, not foot slopes.

3. Floodplains

 Definition: Flat low-lying area along the river formed by repeated deposition during
floods.
 Components:
o Active floodplain: River bed area, regularly flooded.
o Inactive floodplain: Higher ground, flooded occasionally.
 Deposition Types:
o Channel deposits: Coarse, in old/abandoned channels.
o Flood deposits: Fine, laid by overbank flow (silt & clay).
 Delta plains: Floodplains in delta regions.

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4. Natural Levees

 Definition: Linear ridges of coarse sediments along

riverbanks.
 Formation: From deposition during overbank floods.
 Features:
o Appear like mounds.
o Protect river from spilling over in small floods.

5. Point Bars (Meander Bars)

 Location: Inside bends of meanders (concave side).

 Formation: Deposits laid by slow-moving water.
 Characteristics: Uniform in width, composed of mixed
sediments.

🔁 Difference: Natural Levees vs. Point Bars

Feature Natural Levees Point Bars

Location Along riverbanks Inside bends of meanders

Formation By overbank floods By lateral deposition in bends

Composition Coarse sediments Mixed-size sediments

Shape Linear ridges or mounds Linear and uniform

6. Meanders

 Definition: Sinuous channel patterns, not a landform.

 Formation Conditions:
o Very gentle gradients.
o Unconsolidated alluvial banks.
o Coriolis force (deflects flow).
 Erosion & Deposition:
o Concave bank (outer bend): Erosion → cut bank
o Convex bank (inner bend): Deposition → point bar
 Evolution:
o Deep meanders may get cut off → form ox-bow lakes.

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🟦 2. Groundwater (Karst Topography)

🧱 How Groundwater Erodes Landforms

 Groundwater moves vertically (percolation) and then horizontally through joints,

bedding planes, and permeable rocks.
 Mechanical erosion by groundwater is insignificant.
 Chemical erosion through solution and precipitation is the main agent, especially in
calcium carbonate-rich rocks like:
o Limestone
o Dolomite

🏔️ Karst Topography

 Definition: A landform developed due to chemical weathering (solution & deposition)

by groundwater in limestone/dolomite regions.
 Named after: Karst region, Balkans (near Adriatic Sea).
 Karst regions exhibit distinct erosional and depositional features due to groundwater
action.

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🌍 EROSIONAL LANDFORMS — KARST TOPOGRAPHY

🌀 1. Pools, Sinkholes, and Dolines

 Swallow Holes: Small to medium, shallow depressions

on limestone surfaces formed by solution.
 Sinkholes:
o Funnel-shaped depressions, circular at the top,
narrower at the bottom.
o Sizes: A few square meters to hectares; Depth:
0.5m to 30m+
o Types:
 Solution Sinks – formed purely by
dissolution.
Figure 2: Doline
 Collapse Sinks (Dolines) – occur when the roof
of an underground cave collapses.
 Quick Facts:
o Covered sinkholes may form shallow pools that behave like quicksand.
o Water drains underground through these holes, forming subterranean streams.

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🌊 2. Uvalas (Valley Sinks)

 Formed when multiple sinkholes/dolines merge

due to slumping or cave roof collapse.
 Appear as elongated depressions or trenches in
limestone areas.

Uvalas (Valley Sinks)

🟦 3. Lapies

 Irregular, sharp ridges, grooves, and trenches on

exposed limestone surfaces.
 Result from differential solution along joints.
 Resemble a jagged rock surface.
 Extensive lapie fields may evolve into limestone
Lapies
pavements—relatively flat, yet cracked surfaces.

🕳️ 4. Caves and Tunnels

 Form where thick beds of limestone are interlayered with other rocks (shale, sandstone,
quartzite).
 Water moves through bedding planes and dissolves limestone, creating horizontal caves.
 Tunnels: Caves with openings on both ends through which underground streams flow.

🌋 Depositional Landforms – Karst Region

When calcium carbonate (CaCO₃)-rich water evaporates or loses CO₂, the dissolved minerals
are deposited inside limestone caves, forming spectacular speleothems (cave formations).

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⛓️ 1. Stalactites

 Form: Hang from the ceiling of caves like icicles.

 Appearance: Broad at the base (near the ceiling), tapering toward the tip.
 Formation: Created by dripping calcium-rich water depositing minerals as it trickles
down.

🟦 2. Stalagmites

 Form: Grow upward from the floor of the cave.

 Formation: Result from water droplets falling from the stalactites, depositing minerals
on the ground.
 Shape: Can resemble columns, discs, or even have crater-like tops.

🗼 3. Pillars/Columns

 Formed when stalactites and stalagmites fuse together.

 Appear as solid, vertical structures of varying shapes and diameters.

📌 Key Process:

Calcium carbonate (CaCO₃) dissolves in carbonic acid (H₂CO₃) (from CO₂ + rainwater) →
later precipitates when water evaporates or loses CO₂ inside caves.

🟦 3. Glaciers

🔸 Depositional Landforms

The topic "Depositional Landforms" in glaciated regions covers the various landforms created
by the deposition of sediments by glaciers and meltwater. Here's a detailed explanation based on
your text:

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1. Glacial Till and Outwash Deposits

Outwash Deposits
Glacial Till

 Glacial Till: This is the unstratified/ अस्तरित and unassorted/ मिमित नहीं debris (a mix of
fine and coarse materials) directly deposited by melting glaciers. The rock fragments are
angular to sub-angular due to minimal transport.
 Outwash Deposits: These are stratified and sorted sediments laid down by meltwater
streams from glaciers. The particles are generally rounded due to water transport.

2. Moraines

Moraines are accumulations of glacial till that form various types of ridges:

 Terminal Moraine: Deposits found at the end of a glacier; they mark the glacier’s furthest
advance.
 Lateral Moraine: Found along the sides of glacial valleys, parallel to the direction of ice
flow.
 Medial Moraine: Found in the center of a glacial valley, formed when two glaciers merge
and their lateral moraines combine.
 Ground Moraine: An irregular blanket of till spread across the valley floor as the glacier
retreats.

👉 Lateral and terminal moraines can form a horse-shoe shaped ridge when they meet.

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3. Eskers

 Eskers are long, sinuous ridges made of sand

and gravel deposited by meltwater streams
flowing beneath the glacier.
 These streams do not cut valleys but flow
within ice-walled channels.
 When the glacier melts, the sediments are left
behind as raised ridges.

4. Outwash Plains

 These are broad, flat plains formed by

glacio-fluvial deposits like sand, silt, clay,
and gravel.
 Located at the foot of glacial mountains or
beyond ice sheet margins.
 They result from the joining of several
alluvial fans formed by meltwater streams.

5. Drumlins

 Drumlins are streamlined, oval-shaped hills of glacial till.

 Stoss End: The steeper and blunter end that faces the direction of ice movement.
 Tail End: The gentler, tapered end pointing away from ice movement.
 They form when debris is dumped under heavy ice pressure.
 Drumlins indicate glacier flow direction.

Summary Table

Landform Formed By Key Features

Till Glacier itself Unsorted, angular fragments
Outwash Meltwater streams Sorted, stratified, rounded fragments
Moraine Glacial till Ridges (lateral, terminal, medial, ground)
Esker Subglacial meltwater Sinuous ridge of sorted material
Outwash Plain Glacio-fluvial action Flat plains of sand, silt, gravel
Drumlin Subglacial deposition Oval-shaped hills, show ice direction

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🟦 4. Waves and Coastal Currents

🌊 WAVES AND COASTAL PROCESSES – EXPLAINED

1. Coastal Processes Are Dynamic and Destructive

 Coastal areas are among the most rapidly changing landscapes on Earth.
 Erosion and deposition happen continuously—sometimes erosion occurs in one
season, and deposition in another at the same place.

2. Role of Waves

 Waves are the primary agents of coastal change.

 When waves break (especially near the shore), they:
o Hit the coast with immense force.
o Churn sediments on the seabed.
o Cause erosion, transportation, and deposition of materials.

👉 The impact of breaking waves is powerful enough to reshape coastlines.

3. Types of Waves and Their Effects

 Normal Waves: Constantly modify the shore through regular action.

 Storm Waves: Stronger, occur during storms, cause sudden erosion and coastal damage.
 Tsunami Waves: Extremely powerful, transform coastlines rapidly, often leading to
major destruction in hours.

4. Other Influences on Coastal Landforms

Besides wave action, coastal landforms also depend on:

(i) Configuration of Land and Seafloor

 Shape and slope of both land and ocean floor determine how waves act.
 For example, steep coasts face stronger erosion, while gentle slopes favor deposition.

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(ii) Nature of Coastline Movement

 Emerging Coast (land rises or sea level falls): New land appears; generally, forms
gently sloping, sedimentary coasts.
 Submerging Coast (land sinks or sea level rises): Water invades land; leads to rocky or
cliffed coasts.

5. Two Basic Types of Coasts

Type of Coast Characteristics Example Features

High, Rocky Coasts Cliffs, wave-cut

Steep, rugged, deeply eroded by wave action
(Submerged) platforms

Low, Smooth Coasts Flat or gently sloping, formed by sediment

Beaches, spits, lagoons
(Emerged) deposition

Mumbai and Konkan Coast (Maharashtra)

– Some parts show features of submergence, like drowned valleys. Parts of the
Gujarat coast
– Some areas show evidence of emergence due to tectonic uplift.

Here's a clear and structured explanation of the topic:

🌊 High Rocky Coasts vs. Low Sedimentary Coasts

Coastal areas can be broadly categorized into two types based on their topography and the
dominant coastal processes:

 High Rocky Coasts – where erosion dominates

 Low Sedimentary Coasts – where deposition dominates

🟦 1. High Rocky Coasts (Erosional Coasts)

Characteristics:

 Found where land rises steeply from the sea.

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  Coastlines are irregular and indented, especially where glacial valleys (like fjords) are
present.
 No depositional landforms in the initial stages – erosion is the key process.

Formation and Features:

 Waves hit the cliffs with great force, carving sea cliffs and wave-cut platforms.
 Over time, cliffs recede due to continued erosion.
 Fallen rock fragments get broken down into rounded pebbles, and are deposited
offshore.
 As cliffs erode and coastlines smoothen, wave-built terraces can form.
 Materials carried by waves and longshore currents form:
o Beaches
o Bars (submerged ridges of sand parallel to the coast)
o Barrier bars (visible above water)
o Spits (narrow ridges of sand attached to the land at one end)
o Lagoons (when spits/bars block bays)
 Lagoon → filled with sediment → coastal plain

📌 Example: Western coasts of Norway (fjords), parts of

Western USA and Canada.

Figure 3 Western coasts of Norway (fjords),

🏖️ 2. Low Sedimentary Coasts (Depositional

Coasts)

Characteristics:

 Found where rivers deposit large amounts of sediment near the sea.
 Coastline is smooth, gently sloping, with low elevation.
 Dominated by depositional processes.

Formation and Features:

 Rivers build coastal plains and deltas.

 Presence of lagoons, tidal creeks, swamps, and marshes is common.
 Wave action stirs the sediments, forming:
o Bars
o Barrier bars
o Spits

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 o Lagoons (eventually turn into swamps and then coastal plains)
 Large rivers deposit enough material to create deltas (e.g., Ganga-Brahmaputra delta).
 Storms and tsunamis can rapidly change landforms even here.

📌 Example: Eastern coast of India (e.g., West Bengal, Odisha), Nile Delta (Egypt), Mississippi
Delta (USA).

📊 Summary Table

Feature High Rocky Coasts Low Sedimentary Coasts

Dominant Process Erosion Deposition

Coastline Shape Irregular, indented, steep Smooth, gently sloping

Common Landforms Cliffs, wave-cut platforms, fjords Beaches, bars, spits, lagoons, deltas

Example Landforms Wave-built terraces, barrier bars, spits Coastal plains, marshes, tidal creeks

Sediment Supply Limited, from cliff erosion Abundant, from river deposition

Typical Examples Western Norway, Western USA Ganga-Brahmaputra delta, Nile delta

🌊 EROSIONAL LANDFORMS

These landforms are created when strong waves continuously hit the coastline, wearing away
rocks and soil. Over time, waves cut into cliffs and shape the coast.

🟦 1. Cliffs

 Definition: Steep, high rock faces formed

by constant wave erosion.
 Formation:
o Waves crash into the base of a rock
face.
o The force undercuts the rock.
o Eventually, the upper part collapses,
forming a cliff.
 Height: Can range from a few metres to over
30 m.

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🟦 2. Wave-cut Terraces

 Definition: Flat or gently sloping rocky

platforms at the base of a sea cliff.
 Formation:
o As cliffs erode and retreat, a flat surface
is left behind.
o These are formed above average wave
height due to continued erosion and
cliff retreat.

🕳️ 3. Sea Caves

 Definition: Hollow spaces or tunnels carved into the cliff face.

 Formation:
o Wave action and rock debris smash against weak parts of the cliff.
o Over time, the hollow deepens into a
cave.

🗿 4. Sea Stacks

 Definition: Isolated vertical columns of rock

standing in the sea near the coast.
 Formation:
o Formed when sea caves collapse and cliffs
recede, leaving behind resistant rock
remnants.
o These are former parts of the cliff.
 Nature: Temporary – eventually destroyed by
wave action.

📉 How the Coast Evolves:

1. Waves erode base of headlands → sea caves

form.

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 2. Caves widen and roof collapses → cliff retreats.
3. Isolated rock columns left behind → sea stacks.
4. Continued erosion forms wave-cut terraces.
5. Cliff retreats inland, flattening coast.
6. In time, erosional landforms disappear, replaced by:
o Coastal plains,
o Sandy or shingle beaches (from debris).

✅ Summary Table

Landform Formation Process Key Feature

Cliff Waves erode base of rock Steep face, up to 30 m or more

Wave-cut terrace Cliff recedes, leaves flat surface Rocky platform above wave height

Sea Cave Waves hollow out weak cliff areas Hollow in cliff face

Sea Stack Erosion isolates part of cliff Pillar-like rock in the sea

🌊 DEPOSITIONAL LANDFORMS ALONG COASTS

Deposition occurs when the sea loses its energy and drops the sand, pebbles, and other material it
has been carrying. These materials accumulate to form various landforms.

🏖️ 1. Beaches

 Definition: Gently sloping shorelines formed by accumulation of sediments like sand,

gravel, or pebbles.
 Origin of Sediments: From rivers, streams, or erosion of coastal cliffs by waves.
 Nature:
o Temporary features—they can change seasonally.
o Sandy beaches: Fine sand, more stable.
o Shingle beaches: Made of pebbles and cobbles, coarser and steeper.
o

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🌬️ 2. Sand Dunes

 Location: Found just behind the beach on low-

lying coasts.
 Formation:
o Wind lifts dry sand from the beach.
o This sand is deposited as dunes, forming
ridges parallel to the coast.
 Common in: Low sedimentary coasts like
Gujarat or Tamil Nadu coasts in India.

🏝️ 3. Bars

 Definition: A ridge of sand or shingle deposited offshore, parallel to the coast.

 Formation: Waves deposit sediments in shallow water away from the shore.
 Offshore bar: Underwater ridge.
 Barrier bar: When enough sand accumulates, it rises above sea level.

🛡️ 4. Barrier Bars

 Definition: Offshore bars that emerge above water and block river mouths or bays.
 Effect: Can protect coastlines from waves (natural breakwaters).

🔁 5. Spits

 Definition: A narrow strip of sand or shingle projecting from the coast into the sea,
attached to land at one end.
 Formation:
o Formed by longshore drift (waves pushing materials along the shore).
o Often curve due to wave action or tidal currents.
 When attached to a headland or enclosing a bay: Becomes a spit.

🏞️ 6. Lagoons

 Definition: Shallow water bodies separated from the sea by a barrier bar or spit.
 Formation: Spits or barriers block off a bay or estuary.
 Fate:
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 o Over time, lagoons fill with sediments (from rivers, waves, wind).
o Gradually become swamps or coastal plains.

🌍 How These Features Evolve:

1. Waves deposit sand → beaches form.

2. Wind lifts sand → dunes form.
3. Sediment accumulates in shallow sea → bars/barriers form.
4. Bar extends into sea → forms spit.
5. Spit/bar closes a bay → lagoon forms.
6. Lagoon fills with sediment → turns into coastal plain.

✅ Summary Table

Landform How it Forms Characteristics

Beach Sand deposited by waves Temporary, may be sandy or pebbly

Sand Dune Wind-blown sand behind beach Long ridges, parallel to coast

Bar Sediment ridge offshore Usually underwater, parallel to shore

Barrier Bar Bar that rises above sea level Can block bays/river mouths

Spit Longshore drift forms sand projection Narrow, curved, attached at one end

Lagoon Bay enclosed by bar/spit Shallow water body, becomes swamp/plain

🌬️ WINDS AS A GEOMORPHIC AGENT IN DESERTS

In hot deserts, wind is one of the most powerful and active agents of landform development
due to the dry and barren nature of the landscape.

🔥 Why Wind is So Active in Deserts?

 Desert floors heat up rapidly due to lack of moisture and vegetation.

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  Heated surface → hot air rises → causes turbulence and eddies.
 Wind moves with great speed across flat surfaces.
 Obstacles (like rocks, dunes) create whirlwinds, updrafts, and downdrafts.

💥 Processes of Wind Erosion

1. 🌀 Deflation
o Definition: Lifting and removal of loose particles like dust and sand.
o Result: Lowers land surface, can form deflation hollows or desert pavements.
2. 🟦 Abrasion
o Definition: Sand and silt carried by wind scrape and polish rock surfaces.
o Works like natural sand-blasting.
o Produces smooth surfaces and unique shapes.
3. 🚀 Impact
o Definition: The force of sand particles hitting rocks.
o Can cause chipping or pitting of rock surfaces.

⛈️ Role of Water in Deserts

Even though deserts are dry, when it rains, it pours—literally.

 Rainfall is torrential and short-lived.

 Leads to sheet floods or sheet wash (broad, shallow water flow).
 Causes mass erosion and removal of weathered debris.

🔄 Combination of Wind and Water:

 Wind: Moves fine materials (sand, silt).

 Water: Moves larger debris through brief flash floods.
 Desert rocks weather quickly due to diurnal temperature changes (very hot days and
cold nights).

🏜️ Desert Stream Channels

 Broad, shallow, and undefined.

 Flow only briefly after rain.
 Called ephemeral streams (temporary).

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🌵 EROSIONAL LANDFORMS IN DESERTS

Desert landscapes are shaped not just by wind, but also by occasional water action. Here are the
major wind-formed erosional landforms:

1. 🟦 Pediments and Pediplains

 Pediments:
Gently sloping rocky surfaces found at the base of mountains in deserts, often covered
with a thin layer of sediment.
 Formation:
Created by erosion through sheet flooding,
stream activity, and weathering at the
mountain front.
 Backwasting: The mountain slope retreats
parallel to itself due to weathering and
erosion, extending the pediment backward.
 Pediplain:
A large, flat surface that develops after
prolonged erosion of multiple pediments
and mountain fronts.
Only small hills or inselbergs (isolated
residual hills) remain.

2. 🌊 Playas (Salt Flats)

 Definition:
Flat-floored desert basins that temporarily fill with water during rains.
 Features:
o Water evaporates quickly, leaving salts behind.
o These alkali flats may appear white or crusty due to salt layers.
 Formation:
o Sediments carried from basin margins settle at the center.
o Infrequent rain creates a shallow lake → dries up → forms a playa.

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3. 💨 Deflation Hollows and Caves

 Deflation:
The removal of loose materials (dust, sand) by strong, consistent wind.
 Deflation Hollow:
Shallow depressions formed by removal of surface materials.
 Blowouts and Wind Caves:
o Small pits formed by deflation.
o These may grow deeper and wider to form wind-eroded caves.

4. 🍄 Mushroom, Table, and Pedestal Rocks

These are isolated rock formations sculpted by wind abrasion and deflation, with varying
resistance to erosion.

 Mushroom Rock:
o Narrow stem with a wider cap.
o Lower part eroded more due to sand-blasting near the ground.
 Table Rock:
o Broad, flat upper surface.
o Looks like a table top supported by a narrow base.
 Pedestal Rock:
o Similar to mushroom rocks but not as rounded.
o Formed from harder rock layers resisting erosion more effectively than softer
ones below.

🧱 Summary
Feature Shaped by Characteristics

Pediments Sheet floods, erosion Gently sloping rock floors at mountain bases

Pediplains Long-term erosion Flat desert plains with rare inselbergs

Playas Water + evaporation Shallow seasonal lakes, salt-covered

Deflation Hollows Wind deflation Shallow pits from removal of loose particles

Mushroom/Table Rocks Wind abrasion Unusual rock shapes sculpted by wind-blown sand

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🌬️ Depositional Landforms by Wind (Aeolian Deposition)

Wind is a powerful sorting agent. As it picks up and carries different sizes of sand grains:

 Larger grains roll or bounce (saltation).

 Smaller grains remain suspended in air.
 As wind speed slows, grains settle based on their size and weight—leading to well-sorted
deposits.

These conditions, combined with steady wind and a good sand supply, form distinct sand
dune types.

🏜️ Types of Sand Dunes

1. Barchan Dunes (🌙 Crescent-shaped)

 Shape: Crescent with horns/wings pointing

downwind.
 Conditions: Constant, moderate wind over a flat,
dry desert surface.
 Movement: Slowly migrates in wind direction.
 Example: Common in Sahara.

2. Parabolic Dunes (Reverse Barchans)

 Shape: Crescent, but horns point upwind.

 Formed: Where sand is partially stabilized by vegetation.
 Wind: Same as barchans, but vegetation reverses the wing direction.
 Example: Coastal and semi-arid areas.

3. Seif Dunes (Sword-shaped)

 Shape: Similar to barchans but with only one wing.

 Formation: Result of changing wind directions or variable supply.
 Feature: Can grow very long and high.
 Seif means "sword" in Arabic.

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4. Longitudinal Dunes

 Shape: Long, narrow ridges parallel to the wind.

 Conditions: Poor sand supply but consistent wind.
 Size: Can stretch for kilometers, but relatively low in height.

5. Transverse Dunes

 Shape: Ridges aligned perpendicular to wind.

 Conditions: Plenty of sand, consistent wind from one direction.
 Appearance: Long and wide, low in height.
 Example: Found near sand seas (ergs).

🏠 Stabilized Dunes

 Some dunes, especially near villages or oases, become stabilized:

o By vegetation or human settlement.
o Prevent further movement.

🧱 Summary Table
Sand
Dune Type Shape Wind Direction Key Feature
Supply

Crescent (horns Constant,

Barchan Moderate Freely migrating dunes
downwind) moderate

Parabolic Crescent (horns upwind) Same as barchan Moderate Stabilized by vegetation

Elongated, high, with one

Seif Crescent with one wing Variable Limited
wing

Stretch for kilometers, low

Longitudinal Long ridges (parallel) Constant Low
height

Transverse Ridges (perpendicular) Constant Abundant Wide and long, low in height

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UPSC Mains Type Questions – Landforms

1. Geomorphic Processes & Evolution

Q1. Discuss the role of geomorphic agents in the evolution of landforms. How do climatic and
tectonic factors influence these processes?

Answer: The geomorphic agents such as Wind, Running, Water, Glacier, Waves, Groundwater
play crucial role in the evolution of land. The role of Geomorphic agent in shap

Q2. "Landforms are not static but evolve in stages." Explain the stages of landform development
with examples from riverine and glacial landscapes.

2. Fluvial Landforms

Q3. Explain the transformation of erosional fluvial landforms from rills to floodplains. How does
river rejuvenation affect this sequence?

Q4. Differentiate between incised meanders and ox-bow lakes in terms of formation,
characteristics, and associated stages of river development.

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Q5. How do river terraces form? What do they indicate about the past climatic and tectonic
history of a region?

3. Karst Topography

Q6. With the help of diagrams, describe the formation and evolution of erosional and
depositional features of Karst topography.

Q7. How does groundwater act as a geomorphic agent in limestone regions? Discuss with
suitable examples from India.

4. Glacial Landforms

Q8. Examine the characteristics of U-shaped valleys and moraines. How do they reflect the
intensity and direction of glacial movement?

Q9. Drumlins and eskers are diagnostic of glacial deposition. Discuss their mode of formation
and significance in reconstructing past glacial environments.

5. Aeolian (Wind) Landforms

Q10. Describe the erosional and depositional landforms formed by wind action in desert regions.
Highlight the role of wind direction and sand availability.

Q11. Compare and contrast Barchan and Seif dunes in terms of shape, wind direction, and
environmental conditions.

6. Coastal Landforms

Q12. Coastal processes are both constructive and destructive. Discuss this statement with
reference to cliffs, wave-cut terraces, spits, and lagoons.

Q13. How do depositional coastal landforms reflect the dynamic interaction between wave
action, sediment supply, and topography?

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