UNIT – 5

5.1 Fluvial Landforms

• In humid regions , which receive heavy rainfall running water is considered the
most important of the geomorphic agents .
• There are two components of running water :-
1) Overland flow on general land surface as a sheet
2) Linear flow as streams and rivers in valleys

• Approximately 68% of the land on Earth is drained by rivers that empty into the
oceans. The river’s source is typically located in an area of upland terrain with a
slope for runoffs.
• As a result, the uplands serve as the rivers’ catchment areas, and the mountain
crest serves as the watershed from which the streams descend. The subsequent
stream is the first stream that forms as a result of the slope.
• Several tributaries from either side join the stream as it wears down the
surface. In fluvial geomorphology, the drainage basin or watershed is a key
landscape component.
• Running water is regarded as the most significant geomorphic factor in causing
the degradation of the ground surface in humid locations that get heavy rainfall.
Running water consists of two parts. One is a sheet-like overland flow on the
overall ground surface.
• The majority of water-induced landforms that are the result of erosion are
linked to rivers that are active and young and flow through terrain with a steep
gradient.

• As a result of ongoing erosion, stream channels with steep slopes gradually

become smoother and lose velocity over time, which encourages active
deposition. Streams flowing across steep slopes could be related to depositional
forms.

➢ River course

#plunge pools
 ➢ Fluvial Erosive Action Effects
• Rocks are eroded by the force of flowing water, which is hydration.
• Weathering is caused by a chemical reaction known as corrosion or
solution.
• When materials are being carried, attrition refers to the wear and tear
that occurs when they roll into one another and collide.
• Rocks are worn down by corrosion or abrasion caused by a heavy river load
striking them.
• Vertical erosion known as downcutting: is the eroding of a stream’s base
(downcutting leads to valley deepening).
• The eroding of a stream’s side walls is known as lateral erosion (leads to
valley widening).
• Headward erosion is the erosion of a stream channel’s origin, which moves
the origin back from the stream’s flow direction and lengthens the stream
channel as a result.
• Gorges, canyons, waterfalls, rapids, and river capture are examples of
fluvial eroded landforms.
• The mechanical loosening and sweeping away of materials by river water is
known as hydraulic action. It mostly happens by rushing into rock crevices
and cracks and eroding them.

➢ Fluvial Landform types

There are two types of Fluvial Landforms:

[A] Fluvial Erosional Landforms

1. River Valleys

A river valley is an extensive ground depression through which a stream travels

throughout the entirety of its course. As the erosional cycle progresses, the valley
develops several profiles. The valley is deep, and narrow, and has steep, wall-like sides
and a convex slope when it is young.

Most of the erosional action in this area is vertical down-cutting in nature. This valley
has a typical “V”-shaped valley profile.

The valley floor flattens as the cycle reaches maturity and the lateral erosion
becomes noticeable. With a broad base and a concave slope, the valley profile now
takes on a characteristic “U” shape.
2. Gorge

These valleys are called “I-shaped valleys” because they form an “I” shape when their
sides are nearly parallel to one another. A gorge is a deep valley that is narrow and has
steep, straight sides. The breadth of a gorge is about equal at both its top and
bottom. Hard rocks are where gorges are formed.

Example: Indus Gorge in Kashmir

3. Potholes

Potholes, which are typically cylindrical in shape, are kettle-like tiny depressions in the
rocky river valley bottoms. Sandstones and granites, which are examples of coarse-
grained rocks, are where potholes typically occur.

When caught in water eddies or whirling water, grinding tools (rock fragments, such as
boulders and angular rock pieces) begin dancing in a circular motion and drill and grind
the rock beds of valleys like a drilling machine.

This process is known as potholing or pothole-drilling. Thus, they create tiny holes that
eventually get larger as the aforementioned action is repeated. The potholes continue
to become deeper and wider.

4. Gulleys/Rills

An incised water-worn channel known as a gulley is typical of semi-arid regions. It

develops when water that overflows from the land
rushes down a slope, particularly after a lot of rain,
and is condensed into rills that then combine and
widen to form a gulley. Examples: the ravines of
Chambal Valley in Central India.

5. Ox-Bow Lake

The outer curve of a meander can occasionally be

increased by vigorous erosion to the point where the
inner ends of the loop are close enough to the main
river to become an isolated water body. In due course,
these bodies of water turn into swamps. In the Indo-
Gangetic plains, Ganga’s southerly movement has left a
number of ox-bow lakes to the north of the river’s current route.
6. Incised Meanders

Normally, erosion is concentrated in streams that move quickly over steep grades.

on the stream channel’s floor. Additionally, compared to streams flowing on low and
mild slopes, lateral erosion on the sidewalls of valleys is less for streams flowing on
steep gradients. Active lateral erosion causes streams moving over mild slopes to take
a winding or sinuous paths. Where stream slopes are fairly mild, meandering streams
frequently cross floodplains and delta plains. However, hard rocks can also have
meanders that are carved quite deeply and broadly. Incised or entrenched meanders
are the name given to these meanders.

7. River Terraces

River terraces are levels that represent former floodplain or valley floor levels. They
could be terraces made of stream deposits or bedrock surfaces devoid of any alluvial
cover. River terraces are essentially a result of erosion since a stream’s vertical
erosion into its own depositional floodplain causes them to form.

Such terraces may be numerous and vary in height, showing the levels of an earlier
river bed. When the river terraces are found at the same elevation on both banks of
the rivers, they are referred to as paired terraces.

8. Peneplain

This describes an undulating, featureless plain that is dotted with small, remnant hills
made of hardy rocks. In periods of prolonged tectonic stability, the peneplain is
designed to suggest the portrayal of
a close-to-final (or penultimate)
stage of river erosion.
[B] Fluvial Depositional Landforms
Stream velocity and the amount of river load have an impact on how much
sediment is deposited by a stream. As a result of being compelled to leave more
cargo to settle, streams with lower stream velocity have less carrying power.
Increased sediment load in downstream sections of rivers is caused by
(i)accelerated rate of erosion in source catchment areas as a result of
deforestation;
(ii) supply of glacio-fluvial materials;
(iii) supply of additional sediment load by tributary streams; and
(iv) gradual increase in stream sediment load as a result of rill and gully erosion.

1. Delta
A delta is an area of alluvium near the mouth of
a river where more material is dumped there
than can be taken away. A network of channels
is created by splitting the river into two or
more channels (distributaries), which may then
split again and again.

2. Meanders
A river channel’s pronounced curve or loop is
referred to as a meander. The term “cliff-
slope side” refers to the outer bend of a
meander that is marked by severe erosion
and vertical cliffs. The slope on this side is
concave. The inner side of the loop is known
as the slip-off side and is characterised by
deposition and a mild convex slope. The
meanders may have wavy, horse-shoe, ox-bow,
or bracelet-shaped morphologies.

3. Alluvial Fans and Cones

A stream’s velocity drops because of a reduced gradient as it departs the
mountains and descends to the plains. As a result, near the foothills, it sheds a
significant amount of the stuff it was carrying from the mountains. This
material is deposited in a conical shape, resembling a series of continuous fans.
They are referred to as alluvial fans. These fans can be seen all over the north
Indian plains, at the foothills of the Himalayas.
4. Natural Levees, Floodplains, and Point Bars
A floodplain is created through deposition, much as valleys are created by
erosion. A significant river-depositing
landform is a floodplain. When a stream
channel changes from a flat surface to a
slight slope, larger items are deposited
first. As a result, fine-grained materials
like sand, silt, and clay are typically
carried by relatively slow-moving streams
in kinder channels that are typically found
in the plains, where they are then dumped
over the bed and during flooding above
the bed. The active floodplain is a bed of river deposits. Over the bank, there is
an inactive floodplain.

5. Doab
The area of land that is situated where two rivers converge. Doab is a name for
the “tongue” or tract of land located between two converging rivers that is used
in South Asia, mainly in India and Pakistan.
5. 2 Aeolian Landforms
• The wind moulds aeolian landscapes (named for the Greek God of wind, Aeolus).
Aeolian processes involve the wind carrying, depositing, and eroding sediment.
Numerous habitats, including the coastal zone, chilly and scorching deserts, and
agricultural areas, are where these activities take place.
• A lack of vegetation cover, a supply of fine sediment (clay, silt, and sand), and
strong winds are common characteristics of these ecosystems.

• The emission and/or mobilisation of dust and the development of sand dunes are
both caused by aeolian processes.

• In order to carry sediment, they rely heavily on other geologic processes

including rivers, glaciers, and waves. In all terrestrial ecosystems, the wind is a
geomorphic agent. It is most active where there is little to no vegetation, fine-
textured soils and sediments, and a dry climate.

➢ Wind action
▪ In scorching deserts, the wind is the primary geomorphic force. Winds
blow more quickly in hot deserts, which leads to erosion and deposition in
the desert. Aeolian Landforms are landforms produced by the wind’s
erosional and depositional processes. This mechanism has been observed
and researched on other worlds, including Mars, and is not specific to the
Earth.

▪ An erg is a wide, flat stretch of desert covered with wind-swept sand

with little to no vegetation cover (also known as a sand sea, dune sea, or
sand sheet if it lacks dunes).
▪ It is characterised as a desert region with more than 125 square
kilometres of aeolian or wind-blown sand and more than 20% of the
surface covered
with sand. “Dune
fields” are smaller
regions.
▪ There are multiple *Aeolian
ergs in the Sahara,
the world’s largest
scorching desert.
➢ Aeolian Landform types
1. Aeolian dunes: These are large mounds or ridges of sand that are formed by
the wind blowing sand particles into a specific area and depositing them in a
particular pattern.
2. Yardangs: These are elongated, streamlined landforms that are created by the
erosion of soft rock or sediment by the wind. They often have a steep, sharp-
edged ridge and a gently sloping windward side.
3. Desert pavement: This is a type of landform where the surface of the ground
is covered by a layer of closely packed pebbles and small stones. It is formed by
the wind blowing away finer particles and leaving behind the larger, heavier
rocks.
4. Blowouts: These are shallow depressions or hollows in the ground that are
formed by the wind eroding the surface material and creating a bowl-shaped
depression.
5. Ventifacts: These are rocks that have been shaped and polished by the
abrasive action of wind-blown sand. They often have flat, smooth surfaces and
sharp edges.
6. Sand sheets: These are extensive areas of flat, sandy terrain that are created
by the wind depositing sand over a wide area. Sand sheets can be found in
desert regions and coastal areas.
7. Loess deposits: These are thick layers of wind-blown silt and clay that have
been deposited
over time.
Loess deposits
can be found in
areas with
strong
prevailing
winds, such as
the central
United States
and parts of
China.
5.3 Glacial Landforms
• Glacial landforms are landforms that are produced by glaciers. The migration of
massive ice sheets throughout the Quaternary glaciations is responsible for
most of the current glacial landforms.
• In areas where there are no active glaciers or glaciation processes at the
moment, glacial landforms can still be found.
• A straight row of stakes placed across a glacier will gradually assume a curved
shape as they descend the valley, demonstrating that the glacier moves more
quickly in the middle than at the edges.

➢ Formation
▪ In locations where more snow accumulates each year than melts,
glaciers start to form. The snow starts to compress right away when it
falls, or it gets denser and more densely packed.
▪ Firnification is the process through which snow condenses into glacial
firn (thick, granular ice). The firn grains combine into a massive mass of
solid ice when the ice gets thick enough, which takes around 50 metres
(160 feet).
▪ The glacier starts to calve as a result of its weight. A glacier’s many
components move at various rates. The glacier’s centre, flowing ice,
advances more quickly than its base.
➢ Characteristics of glacier
1. Slow movement: Glaciers move slowly downhill under the force of gravity,
typically at speeds ranging from a few centimeters to several meters per
day. The movement of glaciers is driven by the weight of the ice and the
deformation of the ice crystals.

2. Accumulation and ablation: Glaciers accumulate snow and ice in their upper
regions through processes such as snowfall and avalanches. This accumulation
of ice is balanced by ablation, which includes melting, sublimation, calving, and
evaporation. The balance between accumulation and ablation determines the
overall size and health of a glacier.

3. Striations and moraines: Glaciers can leave behind distinctive features on

the landscape, such as striations (scratches) on bedrock caused by the
movement of rocks embedded in the ice. Moraines are ridges or mounds of
glacial debris (rock, sediment, and till) that are deposited along the sides or
at the terminus of a glacier.

4. Glacier ice: Glacier ice is formed from compacted snow that has undergone
a process of recrystallization, resulting in a dense, blue-tinted ice. Glacier
ice can flow like a plastic material under pressure and exhibits unique
physical properties due to its formation process.

5. Crevasse formation: Glaciers can develop crevasses, which are deep cracks
or fractures in the ice caused by stress and movement within the glacier.
Crevasse formation is common in areas where the glacier flows over uneven
terrain or changes in slope.

6. Terminal moraine: The terminal moraine is a ridge of glacial debris that

forms at the terminus (end) of a glacier. It marks the furthest extent of
glacier advance and can help geologists reconstruct past glacial activity.

7. Glacier retreat and advance: Glaciers respond to changes in temperature

and precipitation by either advancing or retreating. Climate change can
significantly impact glaciers, leading to accelerated melting and retreat in
many regions around the world.
 8. Glacier erosion: Glaciers are powerful agents of erosion, shaping the
landscape through processes such as plucking (removal of rock fragments),
abrasion (scouring of bedrock), and glacial carving (formation of valleys and
cirques).

9. Icebergs: In marine environments, glaciers can calve icebergs into the water,
creating floating chunks of ice that pose hazards to navigation. Icebergs are
often formed by tidewater glaciers or outlet glaciers that terminate in the
ocean.

10. Glacier dynamics: Glaciers exhibit complex behaviour due to interactions

between ice flow, temperature gradients, basal sliding, and subglacial
hydrology. Understanding glacier dynamics is crucial for predicting future
changes in glacier extent and behaviour.

➢ Erosional landforms

1. U-Shaped Valley

U-Shaped Valley is a typical glacial feature. Since

glacial mass is heavy and slow moving, erosional
activity is uniform in all directions. A steep-sided
curved bottom valley has a U shaped profile.

2. Hanging Valley

Hanging valley is formed when tributary glaciers are unable to cut as deeply as main ones
and remain “hanging” at higher levels than the main valley as discordant tributaries.
These tributary valleys appear hanging over the main valley and enter the main valley at
some height.

3. Cirque and Tarn

A Cirque or Corrie is an amphitheater-shaped hollow basin cut into a mountain ridge. It

has a steep-sided slope on three sides, an open end on one side and a flat bottom. When
the ice melts, the Cirque may develop into a Tarn Lake and the whole thing appears like
a big armchair.
4. Aretes

It is a steep-sided, sharp-tipped saw toothed ridges which have undergone glacial

erosion from two sides. These comb like ridges are called as arete.

5. Horn

If the summit of the Arete is roughly inclined, it gives rise to pyramidal peaks which are
known as horns. Example, Matterhorn of Alps-Switzerland.

6. Roche Moutonnees or Sheep Rock

Roche Moutonnees or sheep rock is a glaciated bedrock surface, usually in the form of rounded
knobs. The upstream side of a roche moutonnee has been subjected to glacial scouring that has
produced a gentle, polished, and striated slope and the downstream side has been subjected to
glacial plucking that has resulted in a steep, irregular and jagged slope.

7. Nunataks

A rock mass surrounded by ice is called Nunatak. It stands out as an island in

the ice.

8. Fjord

The fjord is formed as a steep-sided narrow entrance like feature at the coast of a
glaciated region where the stream meets the coast. Fjords are common in Norway,
Greenland and New zealand.
➢ Depositional landforms

The depositional landforms of the glaciers are;

1. Moraines

Moraines are the piles of dirt and rock that are deposited by a glacier as it moves
across the landscape. These debris fields exist in places where glaciers have moved
through in the past. There are many kinds of glacial moraines that form. Moraines
are generally classified based on their location.

a) Lateral Moraines

Lateral moraines are ridges of debris that run parallel to the sides of a glacier.
This is often accompanied by scraping of the valley sides which means the debris
from the moraine creates high ridges above the glacier.

b) Ground Moraines

Ground moraines are glacial depositions formed on the floor of glacial valley.
Ground moraines can be deposited in between lateral moraines in the case of many
alpine glaciers.

c) Medial Moraines

Medial moraines are ridges of debris that are left down a valley floor at the
middle of two glaciers. Both glaciers merge together and their debris combine to
form a consistent moraine field along their borders. They are actually the merging
of two lateral moraines which continue as medial moraines.

d) Terminal or End Moraines

Terminal or end moraines are left by the end of a glacier. The slower a glacier moves
the bigger the moraine will be as the glacier has more time to accumulate outside
debris.
e) Recessional Moraines

This recessional moraine runs across the landscape behind a terminal moraine.
They are caused by times when the glacier slows or stops in its movement. It is
formed because the receding glacier pauses in certain places for a long time
before continuing its movement.

2. Outwash Plain

When the glacier reaches its lowest point and melts, it leaves behind a layered
deposition of rock debris, clay, sand, gravel, etc. This layered surface is called as
an Outwash Plain.

3. Esker

It is a winding ridge of depositions of rock, gravel, clay, etc, running along a glacier
in an outwash plain. The Eskers resemble the feature of an embankment and are often
used for laying roads.
 4. Drumlins

It is an inverted boat-shaped deposition in an outwash plain caused by deposition.

5. Kames

Kames are the number of ridges formed along the ice front.
5.4 Coastal landforms
• Coastal Landforms are formed where the land meets the sea. A Coastal
Landform is formed by both marine and terrestrial processes.
• There are various types of coastal landforms produced by these processes,
which either cause erosion or deposition.
• The type of rock that these processes are acting on, the amount of energy in
the system, sea currents, waves, and tides are just a few of the variables that
affect how the coastal landscape is formed.

➢ Formation of Sea Waves

▪ Sea waves are undulations of seawater. The waves are caused by friction
between the water and the blowing wind.
▪ As the wind blows, it transfers its energy through friction, causing the water to
move in a circular motion.
▪ As the wave nears the shore, the friction of these circular waves with the
seafloor causes the wave base to slow down. The top of the wave curves over
until the wave crashes and breaks on the shore. Finally, the water recedes into
the sea.
▪ There are two Types of Waves:
❖ Constructive Waves: These waves gently roll over the coasts and help deposition
on the coast.
❖ Destructive waves: These waves roll over the coast with tremendous force and
erode coastal rocks.

➢ Marine Erosion Processes

Abrasion: When the waves strike against the coast with eroded materials
Attrition: when coarse sands and pebbles collide with each other during
transport and break down into finer particles.
Solvent Action: The process of dissolving coastal rocks.
Hydraulic Action: The splashing action of sea waves against the rocks.
➢ Coastal landforms erosional
✓ Chasms: Chasms are narrow and deep indents on the coastline. They are
formed when on the sea-facing side, hard and soh rocks occur in
alternative bands.
✓ Bay: The wave action wears away the soft rocks forming indents. The
chasm widens till it forms a bay.
✓ Capes: The hard rocks which are left in the project as capes in the
seawater.
✓ Sea cliffs: A steep rocky coast rising almost vertically above the
seawater is called a sea cliff.
✓ Wave-cut Platforms: When Sea waves strike a cliff continuously, the
cliff gradually retreats over time. A rock-cut flat surface is formed in
front of the cliff, called a wave-cut platform.
✓ Cave: Sea caves are formed at the base of a cliff. Sea waves erode
softer rocks at the base quickly creating holes or hollows. These hollows
over time enlarge to form sea caves.
✓ Arch: It is formed when two caves develop on either side of projected
rock and ultimately unite.
✓ Stack: When the roof of the arch collapses and the end sides remain
standing, a pillar-like structure on the coast is formed. It is called a
stack.
✓ Stump: When the stack is eroded further, the height of the stack is
reduced to form a stump.
✓ Blow-hole/Gloup: Continued action of sea waves makes holes in the cave
roof. This hole is called a Gloup or blow hole.
✓ Geo: With further erosion, the blowholes enlarge and the roof collapses.
A long, narrow inlet called Geo is developed.
➢ Coastal landforms depositional

✓ Beaches: These are deposits of marine sediments consisting of sand, shingles,

cobbles etc on the seashore.
✓ Spits and bars: A spit is a low-lying ridge of sands and pebbles with one end
connected to the mainland and the other end terminating into the sea.
✓ Hook: A bent spit is called a hook.
✓ Bar: It is a ridge of sand lying parallel to the coast. They are submerged
features.
✓ Tombolo: When a bar extends and joins an island to the mainland or joins two
islands, it is called a tombolo. For example, the Chesil beach in Dorset, England
connects the Isle of Portland with the mainland.
✓ Lagoons: The enclosed area of seawater between a bar and the coast is called a
lagoon. For example Chilka lake on the Odisha coast and Pulicat lake on the
Andhra coast.
Professors when they check female students assignment :-

Professors when they check male students assignment :-