-geomorphology.pptx

 Understand the present
 Interpret the past
 Uniformitarianism
(Present is key to the past)

 Topography refers to the elevation and relief of the Earth’s surface.
 Landforms are the topographic features on the Earth’s surface.
 Geomorphology is the study of earth surface processes and
landforms.
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The maps above represent the same area on Earth’s surface and they show three different ways we can view
landforms. The image on the far left is a clip from a topographic elevation map, the image in the middle is an
infrared aerial photo, and the image on the right is the geologic interpretation of surface sediments and
geomorphology. This location is interesting because it contains elements of a natural and human altered physical
environment. The lake in the image, (coded blue in the topographic and geology map, and black in the infrared aerial
photo) was formed by artificial damming a stream the flows through this landscape.

 Topography is a term used to describe the Earth’s surface. Topography includes a variety of
different features, collectively referred to as landforms.
 Topography is measured by the differences in elevation across the earth’s surface.
 Differences between high and low elevation are referred to as changes in relief.
 Scientist examine topography using a variety of different sources ranging from paper
topographic maps to digital elevation models developed using specialized geographic
information systems commonly referred to as a GIS.
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South Carolina’s elevation relief
ranges from 4,590 feet in the Blue
Ridge Region to 0 feet along the
Coastal Plain. The rivers dissect the
topography and drain
down-slope from headwaters in
the mountainous Blue Ridge and
Piedmont, into the alluvial valleys
of the Coastal Plain before
draining into the Atlantic Ocean.

 Landforms are the individual topographic features exposed on the Earth’s surface.
 Landforms vary in size and shape and include features such as small creeks or sand dunes, or
large features.
 Landforms develop over a range of different time-scales. Some landforms develop rather
quickly (over a few seconds, minutes, or hours), such as a landslide, while others may
involve many millions of years to form, such as a mountain range.
 Landform development can be relatively simple and involve only a few processes, or very
complex and involve a combination of multiple processes and agents.
 Landforms are dynamic features that are continually affected by a variety of earth-surface
processes including weathering, erosion, and deposition.
 Earth scientists who study landforms provide decision makers with information to make
natural resource, cultural management, and infrastructure decisions, that affect humans and
the environment.
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Table Rock Mountain is a metamorphosed igneous intrusion exposed by
millions of years of weathering and erosion in South Carolina’s Piedmont Region.
Photo Source: SCGS

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 First Order of Relief:
 The broadest landform scale is divided into continental landmasses, which include all of the
crust above sea-level (30% Earth’s surface), and ocean basins, which include the crustal areas
below sea-level (70% of Earth’s surface)
 Second Order of Relief:
 The second order of relief includes regional-scale continental features such as mountain
ranges, plateaus, plains, and lowlands. Examples include the Rocky Mountains, Atlantic
Coastal Plain, and Tibetan Plateau.
 Major ocean basin features including continental shelves, slopes, abyssal plains, mid-ocean
ridges, and trenches are all second-order relief landforms.
 Third Order of Relief:
 The third order of relief includes individual landform features that collectively make up the
larger second-order relief landforms. Examples include individual volcanoes, glaciers, valleys,
rivers, flood plains, lakes, marine terraces, beaches, and dunes.
 Each major landform categorized within the third order of relief may also contain many
smaller features or different types of a single feature. For example, although a flood plain is
an individual landform it may also contain a mosaic of smaller landforms including
pointbars, oxbow lakes, and natural levees. Rivers, although a single landform, may be
classified by a variety of channel types including straight, meandering, or braided.

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I. First Order or Relief:
Continental Landmasses and Ocean Basins
II. Second Order of Relief:
Major Continental and Ocean Landforms
III. Third Order of Relief:
Genetic Landform Features
Images and Photos: SCGS
Beaches Rivers and Flood Plains Mountains

 The word “geomorphology" comes from the Greek
roots "geo,“ “morph,” and “logos,” meaning “earth,”
“form,” and “study,” respectively. Therefore,
geomorphology is literally “the study of earth forms.”
 Geomorphologists are concerned primarily with
earth’s surficial features, including their origin, history,
composition, and impact on human activity.
 Geomorphology concentrates primarily on Quaternary
(Pleistocene and Holocene) features.
 Earth’s landforms reflect the local and regional balance
between hydrologic, tectonic, aeolian, glacial,
atmospheric, and marine processes.

 Geomorphology defines the processes and conditions that
influence landform development, and the physical,
morphological, and structural characteristics of landforms.
 Geomorphologists who study landforms often seek to answer
fundamental questions that help them study landforms, such as:
 What is the physical form or shape of the landform?
 What is the elevation and topographic relief of the landform?
 How did the landform originate?
 What is the distribution of the landform and where else does
it occur?
 Are their any patterns associated with the landform or
topography?
 What is the significance of the landform in relation to other
elements of the landscape or environment?
 Has the landform or geomorphology been altered by
humans?
 Does the landform or geomorphology affect humans?

 Uniformitarianism is a common theory held by earth scientists that states “the present is the
key to the past”. Uniformitarianism implies that the processes currently shaping the Earth’s
topography and landforms are the same processes as those which occurred in the past.
 By studying geomorphology, we are better able to interpret the origin of landforms and infer
their future evolution within the landscape.
 Such applications are especially important for predicting, preventing, and mitigating natural
hazards impact to humans, and managing our natural resources for future generations.
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The two images below illustrate the concept of uniformitarianism. On the left is an imprint of ripple marks in
sandstone, similar current ripple forms in the right image. If the present is the key to the past, we can infer
that the sandstone rock formed in a low energy, fluvial environment similar to the conditions in the right
image.

 Maps
 Topographic
 Surface Geologic
 Air photos
 Math Models
 Experiments
 Ground Truth

 Agents
 “that which acts or has the power to act”
 Water and ice, wind
 Subsurface Modifiers
 Tectonic compression, tension and shear
 Processes
 “progressive steps by which an end is attained”
 Weathering, erosion, transport, deposition
 Energy Sources
 Solar, geothermal, gravitational, chemical
Godfrey Ridge East and Brodhead Creek, DWG, PA, , detail

• To understand geomorphological processes of various
environment.
 To detect natural and environmental hazards
efficiently, e.g. earthquake, flooding, landslide,
tsunami, volcanism etc.
 To identify various landform features and landscapes
 To identify various landform features from satellite
images
 Coastal and river research
 Vulnerability studies
 Used in Geology, Geography, Archeology,
Engineering, Planning, Mining, Construction,
Urbanization …

 Observation and hypothesis – Herodotus 450
BC
 Description – Hutton – 1700’s+
 Explanation 1800’s
 Agassiz – glacial landforms
 Powell (1834 -1902) – fluvial/structure
 Gilbert (1843 -1918) – All surfaces
 Correlation
 Davis (1850 -1934) – fluvial+
 Quantification and prediction – now a common
goal
Horn, cirque, col, rock slide, talus
Geomorphology History flashcards

 Rocks on land in Egypt contained
marine fossils.
 Assumed that the
Nile Delta took
thousands of years
to form.

 Dry land can be submerged.
 Land can be raised from beneath the ocean.
 Described erosion by rivers, and deposition in
deltas.

 Lucretius (99-55 BC): Recognized weathering
processes on rocks.
 Seneca (3-65 AD): Observed erosion of valleys
by running water.
 Ibn-Sina (980-1037 AD): Concluded that
mountains could be uplifted, and later eroded.

 Leonardo DaVinci (1452-1519) found marine
fossils on land
 G. Bauer [“Agricola”] (1494-1555) hypothesized
that mountains were sculpted by weathering
and mass movements
 Steno (1638-87) regarded water as the most
significant agent of erosion

 Biblical interpretations hindered the
proliferation of non-catastrophic landform
evolution theories.
 Werner (1749-1817) theorized that all
mountains formed under water as layers of
sediment, , and were ultimately sculpted by
rapidly receding oceans.

 Georges Cuvier: Great catastrophic
floods produced unconformities, and carved
Earth’s landscape.

 Granites form through
heat & fusion deep
underground, and are
later uplifted and
exhumed.
 Landforms are
produced by slow,
continuous processes.
 Uniformatarianism

 Sediments are eroded from
landforms, only to be deposited
and later lithified into new rocks.
 There is neither an apparent
beginning nor end to landform
development.

 John Playfair (1748-1819)
– Illustrations of the Huttonian Theory of the Earth (1802).
– Streams carve their own drainage systems.
– Stream reaches and maintains equilibrium, adjusted to
local gradient. CONCEPT OF “GRADED STREAM”
– The Earth is very ancient; ongoing processes
continue to change it.
 Charles Lyell (1797 - 1875)
The Principles of Geology (1833 - 1875)
A strong promoter of Uniformitarian theory
A vehement opponent of Catastrophism

 Venetz, and Bernardhi: Moraines and erratics
prove glaciations extended from polal
regions(1832)
 Louis Agassiz : Recognized glacial landforms
in Europe & N. Am.- introduced the concept of
Ice Ages (1837)

 Recorded his observations during the voyage
of “the Beagle.”
 Suggested an origin for atolls

• Davis' Cycle of erosion
An example from an arid c

 (1890) Recognized some Utah landscapes were formed
by Pleistocene Lake Bonneville. Great Salt Lake and
Bonneville salt flats are remnants, contributed to the
understanding of river incision, Identified lunar craters
as caused by impacts, and carried out early impact -
cratering experiments
 Landforms are a balance between resisting framework
and the forces acting to alter the landscape
 Implies that time is one component of many that affect
the appearance of the Earth
 Inferred that the landscape was in equilibrium between
driving forces and resisting forces

 Davisian Geomorphology & TIME as the dominant
factor dominated the scientific literature until the
1960’s
 John Hack proposed landscape development occurred
similarly to the way Gilbert had espoused, recognizing
considerable variability in most geomorphic systems
 Most were in Dynamic Equilibrium
 1930-1965 Rise of Quantitative Approaches to
Geomorphology
 Quantitative trends continue (computers, satellite,
other remotely sensed data, numerical methods,
improved dating techniques,…)

 Equilibrium means balance.
 In geomorphology, it refers to no net change,
usually in terms of a balance between
deposition and erosion, uplift and
downcutting, or soil production and removal.
In short, Erosion, transportation and deposition
 Equilibrium is strived for but seldom achieved.
 A change in one part of a system affects all
others.

 Recent uplift in excess of erosional rates results
in a system that is out of equilibrium.
 Weathering and erosion dominate headland
areas with removed material being transported
to a depositional basin.
 As headlands recede, both erosional and
depositional rates decrease.
 If the region remains stable for an extended
period, equilibrium, where erosional and
depositional rates are equal, might be achieved.

 Base level is the level below which erosion
cannot occur and above which deposition does
not take place.
 Sea level is the ultimate base level
 Lakes and reservoirs provide temporary base
levels
 Changes in sea level can be eustatic or relative
 Changes in base level create and destroy
accommodation space

 William Morris Davis (1850-1934)
 Based on Darwinian Evolutionary Theory
 Landscapes evolve throughout time
 Stage of evolution can be determined by
examining the characteristics of the landscape
 Implies that TIME is the critical factor in
determining what the landscape looks like
Structure Process Resulting Time Landform

 Systems
 “an assemblage of parts forming a whole”
 Fluvial, glacial, coastal,
 foreland basin, collisional mountains
 Climate
 Determines dominant agents
 Time
 Reshaping = "Evolution" of landforms/landscapes
 Systems can dominate large areas.
 Regions summarized as Physiography Maps

Concepts in Geomorphology
Concept 1:
‘The same physical processes
and laws that operate today
operated throughout geologic
time (present is key to the
past), although not necessarily
always with the same intensity
as now’ (Thornbury 1969).

Concept 2:
‘Geologic structure is a
dominant control factor in
the evolution of landforms
and is reflected in them’
(Thornbury 1969).

Concept 3:
‘Geomorphic processes leave
their distinctive imprints upon
landforms and each
geomorphic process develops
its own characteristic
assemblage of land forms’
(Thornbury 1969).

Concept 4:
‘As the different erosional
agents act upon the earth’s
surface there is produced an
orderly sequence of landforms
having distinctive
characteristics at the
successive stages of their
development’ (Thornbury
1969).

Concept 5:
‘Geomorphic scale is a
significant parameter in the
interpretation of landform
development and landform
characteristics of geomorphic
systems. Landscape is function
of time and space’ (Singh
Savindra 2007).

Concept 6:
A simple geomorphological
equation may be envisaged
as a vehicle for the
explanation of landform as
follows
F= f (PM) dt (Gregory 1977).

Concept 7:
Complexity of geomorphic
evolution is more common
than simplicity (Thornbury
1969).

Concept 8:
‘Little of the earth’s
topography is older than
Tertiary and most of it no
older than Pleistocene’
(Thornbury 1969).

Concept 9:
‘An appreciation of world
climates is necessary to a
proper understanding of
the varying importance of
the different geomorphic
processes’ (Thornbury
1969).

B. Process Geomorphology:
1. concept of process….the action involved when
a force induces a change (either chemical or
physical) in the materials or forms at the
earth’s surface.
2. Loose definition: ”The study of landforms and
the methods by which the landforms were(are)
created”

A. A delicate balance or equilibrium exists
between landforms and process.
1. Geomorphic Systems
The balance between form and process is best
demonstrated by considering both factors as
systems or component of systems. A system is a
collection of related components

1. G.K. Gilbert – “dynamic
adjustment”
Landforms reflect the interaction between the dominant
process and the local geology

2. William Morris Davis
“cycles of erosion”

3. John Hack
“dynamic equilibrium”

2. Defining Equilibrium and Time Scales
Schumm (1977)

B. The perceived balance between process and
form is created by the interaction of
energy, force, and resistance.
Process: (def) The action involved when a force
induces a change in the materials or
landforms at the Earth’s surface. OR
The method by which one thing may be
produced from something else.

Agents of Geomorphic Processes
 River -Humid Geomorphic Environment
 Wind - Arid Environment
 Glacier/ice - Polar Environments
 Wave - Coastal Environment
Geomorphic processes
 Erosion
 Transportation
 Deposition
Geomorphic products
 Erosional landform features
 Transportation
 Depositional landform features

 Constructive processes build landforms through tectonic and
depositional processes.
 Tectonic processes include movements at plate boundaries, earthquakes,
orogeny, deformation, and volcanic activity.
 Deposition is the accumulation or accretion of weathered and eroded
materials.
 Destructive processes break down landforms through weathering,
erosion, and mass wasting.
 Weathering is the disintegration of rocks by mechanical, chemical, and
biological agents.
 Erosion is the removal and transportation of weathered material by water,
wind, ice, or gravity.
 Mass wasting is the rapid down-slope movement of materials by gravity.
 Other Agents and Processes that Affect Landform Development
 Climate: temperature, precipitation, water cycle, atmospheric conditions
 Time: fast and slow rates of change
 People: influences on natural resources and earth surface processes

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 Constructive processes are responsible for
physically building or constructing certain landforms.
Constructive processes include tectonic and
depositional processes and their landforms.
Tectonic Landforms are created by massive earth movements due to tectonic and
volcanic activity, and include landforms such as: mountains, rift valleys, volcanoes, and
intrusive igneous landforms
Depositional Landforms are produced from the deposition of weathered and eroded
surface materials. Depositional landforms include features such as: beaches, barrier
islands, spits, deltas, flood plains, dunes, alluvial fans, and glacial moraines.
Floodplain deposits at the confluence of
Mississippi and Arkansas Rivers.
The Stromboli Volcano erupting off the coast of
Sicily in the Mediterranean Sea.
Source: wikimedia commons Copyright ©Google Earth 200

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 Destructive processes create landforms through
weathering and erosion of surface materials facilitated by
water, wind, ice, and gravity. Mass-wasting events occur in
areas where weathering and erosion is accelerated.
 Weathering is the disintegration and decomposition of rock at or near the Earth’s
surface by mechanical, chemical, or biological weathering processes.
 Erosion is the removal and transportation of weathered or unweathered materials
by water, wind, ice, and gravity.
 Mass-Wasting is a rapid period of weathering and erosion that removes and
transports materials very quickly and is often triggered by an environmental stimuli.
Mass wasting includes rock falls, landslides, debris and mud flows, slumps, and
creep.
Landforms formed by destructive processes include river
and stream valleys, waterfalls, glacial valleys, karst
landscapes, coastal cliffs, and wave-cut scarps.

Geomorphic Processes:
 Physical processes which create and modify landforms on the
surface of the earth
 Endogenous (Endogenic) vs.Exogenous (Exogenic)
Processes
 Rock Cycle 

Endogenous Processes are large-scale landform
building and transforming processes
– they create relief.
1. Igneous Processes
a. Volcanism: Volcanic eruptions  Volcanoes
b. Plutonism: Igneous intrusions
2. Tectonic Processes (Also called Diastrophism)
a. Folding: anticlines, synclines, mountains
b. Faulting: rift valleys, graben, escarpments
c. Lateral Faulting: strike-slip faults
Earthquakes  evidence of present-day tectonic activity

The forces coming from within the earth are
called as endogenetic forces which cause
two types of movements in the earth, viz,
(i) Horizontal movements, and
(ii) Vertical movements.
Endogenetic forces introduce various types
of vertical irregularities which give birth to
many kinds of relief features on the earth's
surface, eg., mountains, plateaus, plains,
lakes, faults, folds, etc.

On an average, the origin of endogenetic
forces is related to thermal conditions of
the interior of earth. Generally, the
endogenetic forces and related horizontal
and vertical movements are caused due to
contraction and expansion of rocks'
because of varying thermal conditions and
temperature changes inside the earth. The
endogenetic forces and movements are
divided, on the basis of intensity, into two
major categories as in following chart:
•Diastrophic forces (ii) Sudden forces

Diastrophic Forces and Sudden
Forces take place mainly along the
plate boundaries, which are the
zones that are not stable.
Endogenetic processes cause many
major landform features.

Also called Gradational Processes, they comprise
degradation and aggradation – they modify relief
 a continuum of processes – Weathering  Mass
Wasting  Erosion  Transportation  Deposition
 these processes are carried through by Geomorphic
Agents: gravity, flowing water (rivers), moving ice
(glaciers), waves and tides (oceans and lakes), wind,
plants, organisms, animals and humans
1. Degradation Processes  Also called Denudation Processes
a. Weathering , b. Mass Wasting and c. Erosion
and Transportation
2. Aggradation Processes
a. Deposition – fluvial, eolian, glacial, coastal

Sudden Forces
EARTH'S MOVEMENT OR FORCE
Endogenetic Forces
Diastrophic Forces
Epeirogenetic Forces Orogenetic Forces
Exogenetic Forces
Upward Movement
(Emergence)
Downward Movement
(Submergence)
Tensional Forces Compressional Forces
Crustal Fracture Crustal Bending
Cracking Faulting
Warping Folding
(Faults)
(Folds)
Down warping
Up warping

i) Diastrophic Forces
 These forces include both vertical and
horizontal movements which are caused due to
forces deep within the earth. These diastrophic
forces operate very slowly and their effects
become discernable after thousands and
millions of years. These forces also termed as
constructive forces, affect larger areas of the
globe and Produce meso-level reliefs, for
example, mountains, plateau, plains, lakes, big
faults, etc. These diastrophic forces are further
subdivided into two groups, namely,
epeirogenetic movements and orogenetic
movements.

 ii) Sudden forces
 Sudden forces are the result of long
period preparation deep within the
earth. Only their cumulative effects on
the earth's surface are quick and sudden.
Geologically, these sudden forces are
termed as 'constructive forces' because
these create certain relief features on the
earth's surface.


 (A)Epeirogenetic movements:
 Epeirogenetic word consists of two
words, viz: 'epiros' (meaning thereby
continent) and 'genesis' (meaning
thereby original). Epeirogenetic
movement causes upliftment and
subsidence of continental masses
through upward movements are, infact,
vertical movements. These forces and
resultant movements affect larger parts
of the continents. These are further
divided into two types: upward
movement and downward movement.

 (B) Orogenetic movement:
 The word orogenetic has been derived from two
Greek words, ‘oros' (meaning thereby
mountain) and 'genesis' (meaning thereby
origin or formation). Orogenetic movement is
caused due to endogenetic forces working in
horizontal movements. Horizontal forces and
movements are also called as tangential forces.
Orogenetic or horizontal forces work in two
ways, namely,
 (i) in opposite direction, and (ii) towards
each other. This is called 'tensional force'
when it operates in opposite directions. Such
type of forces and movements are also called as
divergent forces.

 Thus, tensional forces create rupture,
cracks, fracture and faults in the crustal
parts of the earth. The-force when
operates face to face, is called
compression force or convergent force.
Compressional force causes crustal
bending leading to the formation of
fields or crustal warping leading to local
rise or subsidence of crustal parts.
 Crustal bending: When horizontal
forces work face to face, the crustal
rocks are bent due to resistant
compressional and tangential forces.

 It is in two ways:
 (i) warping, and (ii) folding.
 The process of crustal warping affects
larger areas of the crust wherein the
crustal parts are either warped
(raised),upward or downward. The
upward rise of the crustal part due to
compressive force resulting from
convergent horizontal movement is
called upwarping. While the bending of
the crustal part downward in the form of
a basin or depression is called down
warping.

Folding
 Folding is one of the endogenetic processes.
When two forces push towards each other from
opposite sides, the rock layers will bend into folds.
The process by which folds are formed are due to
compressional forces known as folding.
There are large-scale and small-scale folds. Large-
scale folds are found mainly along destructive plate
boundaries.

 Faulting is the fracturing and displacement of more brittle
rock strata along a fault plane either caused by tension or
compression.
 A break in rock along which a vertical or horizontal rock
movement has occurred is called a fault.
 The process of forming a fault is faulting.
 The line of fault which appears on land surface is known as
fault line. These lines are often lines of weakness which allow
molten rock to rise up onto the earth surface when there is
active volcanic activity nearby.
 There are three types of fault which are caused by different
endogenetic forces:
 - Normal fault: Compressional force from the plate
 - Reverse fault:Tensional Force from the Plate
 - Tear fault:Diagonal Compressional force from the Plate
 Faulting forms two major landforms - block mountains and rift
valleys.

 Sudden Forces
 Sudden movements, caused by sudden endogenetic forces
coming from deep within the earth, cause sudden and rapid
events that these cause massive distructions at and below the
earth’s surfaces. Such events, like volcanic eruptions and
earthquakes, are called extreme events and become disastrous
hazards when they occur in densely populated localities.
These forces work very quickly and their results are seen
within minutes. It is important to note that these forces are the
result of long-period cumulative effects on the earth’s surface
are quick and sudden. Geologically, these forces are termed as
constructive forces because these create certain relief features
on the earth’s surface. For example, volcanic eruptions result
in the formation of volcanic cones and mountains while
fissure flows of lavas form extensive lava plateaux, such as
Deccan plateau of India and Columbia plateau of USA.
Similarly, it forms the lava plains. Earthquakes create faults,
fractures, lakes, etc.

 An earthquake is a vibration or oscillation of
the surface of the earth caused by sudden
release of enormous pressure.

 Vulcanicity (also known as volcanic activity or
igneous activity) is one of the endogenetic
processes.
 Magma beneath the crust is under very great
pressure. When folding and faulting occur, cracks
or fractures which are lines of weakness. When
these lines of weakness develop downward in the
crust and reach the magma, they will release the
pressure in the magma.
 This allows magma to rise up along the lines of
weakness and intrude into the crust. Some magma
may even reach the earth's surface.
 There are two types of vulcanicity: intrusive
vulcanicity and extrusive vulcanicity.

 In the end, it can be concluded that the plates
are responsible for the endogenetic processes
and landforms, and glacier, river, wind,
atmospheric happenings, etc. are responsible
for the exogenetic process and landforms.

 Diastrophism is also called tectonism, large-
scale deformation of earth’s crust by natural
processes, which leads to the formation of
continents and ocean basins, mountain
systems, plateaus, rift valleys, and other
features by mechanisms such as plate
movement, volcanic loading, or folding.
 Internal forces active here

 Metamorphism is the change in rock structure,
minerals or geologic structure.
 It is a process of change in the physical
structure of rock as a result of long-term heat,
pressure and introduction of chemically active
fluids, especially a change that increases the
rock's hardness and crystalline structure.
 The change occurs primarily due to heat,
pressure, and the introduction of chemically
active fluids.

 Weathering
 Erosion/ Degradation
 Transportation
 Deposition/Aggradation
 Mass movement

 It means to make the things exposed.
 The processes by which the rocks on the earth’s surface
are broken into pieces through the application of
external physical forces and the debris are transported
elsewhere is known as denudation.
 This denudation work is performed through three
processes such as weathering, erosion and
transportation.
 Denudation= Weathering + Erosion + Transportation

 The weathering is a process by which the rocks
on the surface of the earth is broken
mechanically into pieces due to snow or frost,
the variation of temperature and pressure or
due to chemical (dissolution) action on the
materials.
 Even the rocks are dislodged by the animals.
But the rocks weathered this way, are not
transported elsewhere.

 Erosion and transportation are accomplished
together.
 The process by which the rocks of the earth’s
crust are eroded by the river, wind, glacier,
ocean currents etc. are transported elsewhere is
known as erosion.

 Degradation is the lowering of a bottomland
surface through the process of erosion;
 Conceptually it is the opposite of the vertical
component of aggradation and is most
frequently applied to sediment removed from a
channel bed or other low-lying parts of a
stream channel.

 Deposition is the constructive process of
accumulation into beds or irregular masses of
loose sediment or other rock material by any
natural agent;

 Aggradation is the raising or elevating of a
bottomland surface through the process of
alluvial deposition;
 Conceptually it is the vertical component of
accretion and is most frequently applied to
sediment deposition on a channel bed, bar or
other near-channel surfaces, flood plain, or, less
often, low-lying alluvial terrace.

 Sedimentation is the process by which
sediment is mechanically deposited from
suspension within a fluid, generally water, or
ice, thereby accumulating as layers of sediment
that are segregated owing to differences in size,
shape, and composition of the sediment
particles.

 Mass movement is any downslope transfer,
through gravitational and generally water-
facilitated (viscous) processes, of near-surface
soil and rock material; which includes a wide
range of ground movements, such as rock fall,
deep failure of slopes and shallow debris flows,
which can occur in offshore, coastal and
onshore environments.
 Rates of mass movement range from very slow
creep to nearly instantaneous slope failure.

Modification of landforms results from the application
of energy.
Landforms represent the interaction between driving forces and
resistance.
Driving Forces: Climate, Gravity, Forces generated inside the earth
Resistance: Provided by the geologic framework
The link between these two components here is PROCESS

Resisting Forces
Driving Forces
If Fs is greater than 1, bank is stable. If Fs is less than 1 bank will
fail. (We usually add a safety margin – Fs>1.3 is stable.)
Resisting Forces Driving Forces (gravity)
soil strength bank angle
vegetation weight of bank
reinforcement water in bank
Factor of Safety (Fs) =

Think in terms of SPECIFIC
PROCESSES
 On the stream bed
Force/resistance
 On the stream banks
Force/resistance

II. The Basics of Process Geomorphology
C. Changes in the balance between driving
and resisting forces may destabilize the
system. The system may cross a
threshold, and may initiate a new pattern
of equilibrium.

1. Thresholds
Changes in the geomorphic system when the
limits of equilibrium are exceeded
a. Extrinsic Thresholds: caused by external
controlling factors
b. Intrinsic Threshold: usually caused by
internal factors.

 The genetic landform classification system groups landforms by the
dominant set of geomorphic processes responsible for their formation. This
includes the following processes and associated landforms:
 Tectonic Landforms
 Extrusive Igneous Landforms
 Intrusive Igneous Landforms
 Fluvial Landforms
 Karst Landforms
 Aeolian Landforms
 Coastal Landforms
 Ocean Floor Topography
 Glacial Landforms
 Within each of these genetic classifications, the resulting landforms are a
product of either constructive and destructive processes or a combination of
both.
 Landforms are also influenced by other agents or processes including time,
climate, and human activity.
89

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