The document summarizes various aeolian and fluvial landforms and processes. It describes how wind erosion can cause abrasion, deflation, and attrition, shaping landforms like yardangs, desert pavements, and blowouts. Wind can transport materials through saltation, suspension, or traction and deposit them as ripples, loess, or various dune types. Fluvial processes involve erosion, transportation, and deposition by water to form and shape landforms. Young rivers have V-shaped valleys while mature rivers form floodplains and meanders. In old age, rivers flow across peneplains with few landforms.

1. BY – PRAMODA. G, UoM, DoS In Earth Science
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AEOLIAN LANDFORMS
Geomorphic processes: All those physical and chemical changes which effect the modification of the earth
surficial form. It is categorized into two processes-
1. Endogenetic 2. Exogenetic
Geomorphic agent: Any natural medium which is capable of securing and transporting earth material.
Examples: Running water, ground water, glacier, wind, waves, current, tides and tsunami. These agencies may
be designated as mobile agents.
Aeolian processes - It refers specifically to the wind’s ability to shape the surface of the earth.
Winds may erode, transport and deposit materials. Aeolian processes are important in arid and semi-arid
environments such as deserts.
TOPOGRAPHIC EFFECTS OF WIND EROSION
Wind erosion manifests itself in three forms:-
1. Abrasion or corrasion: The wearing down of surfaces by the grinding action and sand blasting of
windborne particles.
2. Deflation: The lifting and removal of loose, fine grained material from the earth surface. Forms
shallow basins called deflation basins.
3. Attrition: Attrition is the grinding action, while on transit wind borne particles often collide with one
another. Such mutual collision brings about a further grinding of the particles.
TRANSPORTATION BY WIND
Three methods:
Saltation: Transported through a series of bounces.
Suspension: particles are lifted high into atmosphere and are carried great distances before they settle.
Rolling or Traction: the movement of particles on ground. The coarser fragments are carried in this
way.
DEPOSITION BY WIND
Reduction in velocity
Any obstruction to wind
Increased load
AEOLIAN LANDFORMS
Features of the earth’s surface produced by either erosive or constructive action of the wind.
Found in regions of the earth where erosionand deposition by wind are the dominant geomorphic forces
shaping the face of the landscape.
Aeolian sediments are oftencomposed of well-rounded, sand to silt sized particles that are weathered by
wind abrasion during transport.
Sediments are deposited when the velocity of the wind falls.
EROSIONAL LANDFORMS

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a) Ventifacts: Formed by abrasion effect. Exhibit one or more polished and faceted surfaces.
They are relatively rare.
b) Yardang: Ridges that are sculpted and streamlined by wind abrasion and deflation.
Elongated in the direction of prevailing wind and are nearly always carved from relatively weak
materials.
c) Mushroom table or pedestal rock: A rock having broad upper and narrow base resembling a
mushroom shape is called mushroom rocks, formed due to abrasive work of wind.
d) Desert pavements or lag deposits: The left behind closely packed, interlocking, angular or
rounded rock fragments of pebble and cobble by wind deflation are known as lag deposits.
A desert pavement is also called “reg” in Western Sahara, “Serir” in Eastern Sahara, “Gibber” in
Australia and “Sai” in Central Asia.
e) Blowouts: Sandy depressions in a sand dune ecosystem caused by the removal of sediments by
wind. Blowouts develop in areas where non-indurated materials lie beneath the land surface.
DEPOSITIONAL LANDFORMS
a) Wind or sand ripples: Miniature dunes within a dune (not more than 2 inches tall).
May form from cross winds and appear to be traveling in a different direction than the large dune.
b) Loess: An Aeolian sediment formed by the accumulation of windblown silt typically in the 20-
50micrometer size range. Buff-coloured, non-indurated, calcareous and permeable. They occur at
variable altitudes and are readily recognized as Aeolian deposits. Loess is the raw material for many
mollisols, the best agricultural soils.
c) Sand dunes: Piles of sand deposited by wind. Leeward side (slipface) has a steeper slope.
Windward side is more gradual.
Different types of dunes
i) Barchan: Crescent –shaped dune whose long axis is transverse to the dominant wind action.
ii) Transverse dunes: Long asymmetrical dunes that form perpendicular to wind direction.
Formed when the source of sand is elongated one and transverse to wind direction.
Single long slipface.
iii)Parabolicdunes: Crescent-shaped dune whose long axis is transverse to dominant wind direction.
Convex in leeward side and concave in windward side. Multiple slip-faces.

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iv) Longitudinal /Seif dunes: A large, elongated dune lying parallel to the prevailing wind
direction. Longitudinal dunes usually have symmetrical cross sections. They generally form in areas
that are located behind an obstacle where sand is abundant and the wind is constant and strong.
v) Star dune: Large pyramidal or star-shaped dune. Has three or more slip-faces. Does not migrate
along the ground, but grows vertically.
vi) Dome: Mound of sand that is circular or elliptical in shape. Has no slipfaces.
vii)Reversing: Dunes that are intermediate between star and transverse dunes. Ridge is asymmetrical
and has two slip-faces.
viii) Coastal dunes: Forms when there is a large supply of beach sand and strong winds blowing
from seato shore. Beach area must be wide. Dissimilar from desert dunes in their form and shape and
in the fact that they do not migrate.
FLUVIAL PROCESSES
As the different erosional agents act upon the earth’s surface there is produced an orderly sequence
of land forms” orderly sequence of erosional features are formed at different stages in fluvial
processes.
Fluvial processes: The set of mechanisms that operate as a result of water flow within a stream
channel, bringing about the erosion, transfer, and deposition of sediment.
Fluvial process is Exogenetic processes which includes
River Erosion
River Transportation
River Deposition
Erosion processes include the displacement of bed particles through drag and lift forces; abrasion,
causing the wearing a way of bed and banks as mobile agencies obtain and remove rock debris

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Transportation: processes include the transfer of material in solution and suspension, and by
saltation.
Deposition: is the geological process by which sediments, soil, and rocks is added to a landform or
land mass.
STAGES OF RIVER
Young stage –
It has steep sided and narrow v-shaped valley created by vertical erosion. Characterized by waterfalls
and rapids. Water is often quit clear because the river is not carrying much load in suspension. Stream
meandering may exist in youth but the meanders in valleys incised below the upland surface.
Waterfalls or rapids may exist where stream courses cross beds of particularly resistant rock.
EROSIONAL LANDFORMS: V-SHAPED VALLEY
Upper zone: large, Angular boulders often block river channels
Produces a large wetted perimeter leads to high friction which uses up much rivers energy
After friction overcome there is little energy is available for eroding and transporting material, and
forms steep slope.
CLASSIFICATION OF VALLEY
Genetic classification:
o Consequent valley: it is one whose course was supposedly determined by the initial slope of
the land newly created
o Subsequent valley: these are valleys whose course have been shifted from the original
consequent ones to belts of more erodible rocks
o Insequent valley: these are valleys which show no apparent adjustment to structural or
lithological control
CLASSIFICATION OF VALLEY BASED ON STRUCTURES
These valleys are classified on the basis of geologic structure:
 Homoclinal valleys: it is also known as strike valleys which follow beds of weaker rock along the
flanks of folds
 Anticline valleys: these are valleys which follow the axes of breached anticlines
 Synclinal valleys: the axes of synclines
 Fault valleys: the streams follow depressions consequent upon faulting
 Fault line valleys: they are subsequent valleys following in fault line
FLUVIAL FEATURES:
– waterfalls & rapids, pools; lakes, canyons & gorges
CANYONS.
 A long, deep, narrow valley with steep cliff walls.
 It cut into the Earth by running water.
 It often having a stream at the bottom.
GORGE
 A gorge is a steep, v-shaped valley formed by the vertical erosion of the land by the river.
 The Indus gorge in Kashmir is the deepest in the world (about 5180 m).

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 If the region is arid where there is little weathering and mass wasting on the valley asides, the
gorge will be impressively deep. If such a gorge is deep, long and u-shaped, we call it canyon.
 Waterfall: a steep drop in the course of a river it has a high head of water and a characteristic
plunge pool at the base waterfalls often form when a band of resistant rocks,
 Knick point : a sharp irregularity in a stream-channel profile, commonly caused by abrupt changes
in bedrock resistance and at which waterfalls starts
 Plunge pool: also known as Waterfall Lake is a pool, lake, or pond that is small in diameter, but
deep. Plunge pools can remain after the waterfall has ceased to exist or the stream has been
diverted.
POTHOLES
 Are depressions that are eroded in to the land rock of the streamed by abrasive action of the
sediment load.
 When a stream is full, the swirling water can cause sand and pebbles to scour out smooth,
cylindrical or bowl-shaped depression in hard rock
 Tend to form in spots where the rock is a little weaker than the surrounding rock. They may
contain certain sand or an assortment of beautifully rounded pebbles.
Maturity stage
 Many tributaries have fed the river upstream.
 The volume of water increases and lateral erosion is taking place
 River channel has become much wider and deeper
 The surrounding valley has also become wider and flatter with a more extensive floodplain
MEANDERS
 Bends or loops in the river
 One of the most distinctive features of the river in the middle course is its increased sinuosity
 Unlike the relatively straight channel of the upper course, in the middle course there are many
meander (bends) in the river
 As water flows into a meander it take on a helical or spiral flow that determines where erosion
and deposition is concentrated
 Slip off slope: a small beach found on the inside of a meander bend where deposition has occurred
in the low energy zone.
 River cliff- a small cliff formed on the outside of a meander bend due to erosion in this high-
energy zone. When the water in an oxbow lake dries.
 An oxbow lake is a U-shaped lake water body formed when a wide meander from the mainstream
of a river is cut off to create a lake. This landform is called an oxbow lake for the distinctive
curved shape that results from this process.
Old stage
 Final stage of a river is reached when the river is flowing on more or less flat surface.
 The speed so low that no net erosion occurs any more. Erosion on the slopes is balanced by
deposition on the floodplains.

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 Peneplain- a flat and relatively featureless landscape with minimal relief;considered to be the end
product of the geomorphic cycle. Peneplain means “almost a plain the process is known as
peneplanation.
 From now on the rivers just sweep over the floodplain and rework the sediment, creating various
floodplain features. Isolated remnants of resistant bedrock may rise over the peneplain surface,
the so called inselbergs.
ALLUVIAL FAN
 Alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and
spreads typically at the exit of a canyon onto a flatter plain.
REJUVENATION
 Old or mature stage landforms may be uplifted due to climate change or tectonic activity
 Entrenched meanders are the result
 Entrenched meander: a winding, sinuous stream valley with abrupt sides.
 Because the river is moving on a flat surface, deposits sediments at the bed often act as barriers
to free flow of water making it to form meanders
DRAINAGE PATTERNS
Dendritic: Irregular branching pattern (tree like) in many direction. It is common in massive rocks and
in flat lying strata Due to strong resistance of rocks headword development of valley is negligible.
Parallel: Parallel or sub-parallel drainage formed on sloping surface. Common in terrain with
homogeneous rocks. Development of parallel rills, gullies or narrow channels are commonly seen on
gently sloping surface
Radial: Streams radiates out from the center of the topographic high common in volcanic terrain
Rectangular:
Channels marked by right-angle bends commonly due to presence of joints and fractures in the
massive rocks (or) foliation in metamorphic rocks.