1. Why the earth is uneven?
Due to internal and external forces earth is changing its surface conditions.
The earth crust is always dynamic
It moves vertically and horizontally
The differences in the internal forces making the surface uneven Wearing down of relief
features are called gradation.
The endogenic forces always elevate parts of the earth‘s surface and hence the exogenic
processes fail to even out the relief variations of the surface of the earth.
Variations remain as long as there is a difference between endogenic and exogenic forces.
The surface of the earth is sensitive. A human being is using surface intensively and
extensively.
GEOMORPHIC PROCESSES
The endogenic and exogenic forces cause physical stress and chemical actions on the earth
material and bring the changes in the configuration of the earth surface is called
GEOMORPHIC PROCESSES
Diastrophism and volcanism are endogenic processes
Weathering, Masswasting, Erosion & Deposition
Are Exogenic Processes
Any Exogenic Element Of Nature Capable Of
Acquiring And Transporting Earth Materials Can
Be Called A Geomorphic Agent.
They Become Mobile When There Is Gradient
The Erosional Agents Are
1.Running Water,2. Moving Ice, 3.Wind,
4.Underground Water,5.Waves
A process is a force applied on earth materials
affecting the same
An agent is a mobile medium which removes
transports and deposits earth materials.
Gravity also causes directional forces activating
downslope movements of matter
Waves and tides are indirect movements of the earth
caused by gravitation
Without gravity and gradient, there is no mobility for erosional agents, as a result, there is no erosion
transportation, and deposition on the earth surface.
All the movements on/in the earth are due to gravitation and gradient. from a higher level to lower
level and high pressure to low-pressure areas
ENDOGENIC PROCESS: the energy generating from within the earth is the main force behind the
endogenic geomorphic processes.
The energy generated due to
1. Radioactivity 2.Rotational Force 3.Tidal Friction 4.Primordial Heat From The Origin Of The
Earth.
Diastrophism And Volvanism Are Due To Geothermal Gradients And Heat Flow From Within The
Earth.
Crustal Thickness, Strength, Action Of Endogenic Forces Are Due To Variations In Geothermal
Gradients And Heat Flow Are Uneven.
DIASTROPHISM: All process that moves elevate or build up portions of the earth‟s crust come under
DIASTROPHISM
THEY ARE TWO TYPES
CHAPTER -6 GEOMORPHIC PROCESSES
45
1.OROGENIC PROCESSES: mountain building through folding
2.EPEROGENIC PROCESS: an uplifting large part of the earth crust
3.EARTH QUAKES
4.PLATE TECTONICS: involve horizontal movements
DIFFERENCE BETWEEN OROGENY AND EPEROGENY
VOLCANISM: Movement of molten rock towards the earth‟s surface and also the formation of many
intrusive and extrusive volcanic forms.
Volcanism: it is the process in which volcanoes takes place
Volcanoes are the landforms formed due to volcanic process
EXOGENIC PROCESSES: They derive their energy from the atmosphere determined by the prime
source The sun and also gradients created by the tectonic factors.
Gravitational force creates gradient towards the downslope direction.
Force applied per unit area is called
STRESS. Stress can be produced in a solid body pushing or pulling
This includes deformation. Forces acting along the faces of earth materials are shear stresses
.(separating forces). It is this stress that breaks rocks and other earth materials. the shear
stress results in angular displacement/slippage. Besides gravitational stress there is molecular
stress which is caused by temperature change, crystallisation and melting .chemical processes
normally lead to loosening of bonds between grains, dissolving of soluble minerals or
cementing materials.
The basic reason for weathering, mass movement erosion and deposition is the development
of stress in the earth materials.
Since there are different climatic regions there is variation in the exogenic process from
region to region. Temperature and precipitation are the two major elements that control
various processes.
All the exogenic process are covered under general term DENUDATION.
The word denude means uncover. Weathering, mass wasting erosion and transportation are
included in denudation.
DENUDATIONAL PROCESSES AND THEIR Driving Forces
In
OROGENY EPEROGENY
The crust is severely damaged
Mountain building process
Folding and faulting
Cause tension and compression
simple deformation
continental formation
upliftment of landmass
vertical force
46
This Chart We Observe That For Each Process There Is Driving Force Called Energy On The Earth
Surface Thermal Gradient Is Caused By
1. Latitude 2.Seasons 3.Land And Water Distribution 4. Angle Of Earth‟s Inclination
The Density of Natural Vegetation Is Greatly Influenced By The Temperature And Precipitation
Helps Indirectly The Exogenic Processes.
THE OTHER FACTORS OF CLIMATIC VARIATIONS ARE1.Altitude 2. Angle Of Slope 3. Ocean
Currents 4.Amount Of Insolation Received By The Region 5. Wind Velocity And Direction 6.
Direction Of The Slope 7. Amount And Kind Of Precipitation 8.Relation Between Precipitation
And Evaporation 9. Daily Rang Of Temperature 10.Freezing And Thawing Frequency 11. Depth
Of Frost Penetration
The Sole Driving Force Behind All The Exogenic Process Is The Sun
When Climatic Factors Are Common The Intensity Of Action Depend On Type And Structure Of
Rocks
STRUCTURE INCLUDES folds, faults, orientation inclination of beds, presence or absence of
joints, bedding planes hardness, the softness of constituent minerals, chemical susceptibility of
mineral constituents, the permeability or impermeability.
Different types of rocks offer varying resistances to various geomorphic processes.
Particular rock may be resistant to one process and non-resistant to another process
As a result, there is varied relief over the earth surface
The effects of exogenic forces may be small and slow but in long run, they have greater effects
Finally, the surface of the earth is operated by different geomorphic processes and at varying
rates
WEATHERING: it is the action of elements of weather on earth materials
Weathering is defined as mechanical disintegration and chemical decomposition of rocks through
the actions of the various element so weather and climate
In weathering, there is no motion of materials takes place so it is in-situ or on-site process
FACTORS INFLUENCING THE WEATHERING& DEPTH OF WEATHERING
1.GEOLOGICAL STRUCTURE 2.CLIMATE 3.TOPOGRAPHY 4. NATURAL VEGETATION
THERE ARE THREE MAJOR GROUPS OF WEATHERING PROCESSES
(I) CHEMICAL (II) PHYSICAL/MECHANICAL (III)BIOLOGICAL WEATHERING
CHEMICAL WEATHERING PROCESSES
A group of weathering processes viz; solution, carbonation, hydration, oxidation and reduction
asc on the roks to decompose, dissolve or reduce them to a fine clastic state through chemical
reactions by oxygen, surface /soil water and other acids. Water and air along with heat must be
present to speed up all chemical reactions.
Over and above the carbon dioxide present in the air, decomposition of plants and animals
increases the quantity of carbon dioxide underground. these chemical reactions on various
minerals are very much similar to the chemical
reactions in a laboratory.
47
SOLUTION: the water /acid with dissolved content is called a solution. This process involves
the removal of solids in solution and depends upon solubility of a mineral in water or weak
acids. when water reacts with any solid many solids may become a solution. Ex. Sulphates,
nitrates, potassium.
When the rain comes these solids dissolve into solution without leaving any residue.
Calcium carbonate, magnesium bicarbonate present in the limestone are dissolved in and form
carbonic acid, produced by decaying organic matter along with soil water greatly aids in this
reaction. Common salt is also susceptible to this process.
CARBONATION: It is the reaction of carbonate and bicarbonate with minerals such as feldspar, &
carbonate minerals from the atmosphere and soil air are absorbed by water to form carbonic
acid.Ca & Mg are dissolved in carbonic acid and washed away to form the caves in limestone region.
Clay minerals are easily eroded due to the presence of minerals which can exchange the ions
with the water.
HYDRATION: it is the chemical addition of water. minerals take up water and expand. this
expansion increases the volume of material. ex. calcium sulphate takes water and converts into
gypsum.it is unstable than calcium sulphate.it is a reversible reaction and when this process
continues for a longer time the materials disintegrate.
Many clay minerals swell and contract during wetting and drying and a repetition of this process
results in cracking of overlying materials. salts in pore spaces undergo rapid and repeated
hydration and help in physical weathering through exfoliation and granular disintegration
OXIDATION AND REDUCTION
Oxidation means a combination of minerals with oxygen to form oxides and hydroxides.
Oxidation occurs when there are sufficient water and atmosphere. EX. Iron, manganese, sulphur,
In the process of oxidation, breakdown occurs due to the addition of oxygen.red colour of iron
becomes into yellow colour. when oxidised minerals re kept in the places where there is no
oxygen reduction takes place. ex. such conditions occur below water table waterlogged areas.
The red colour of iron becomes greenish or bluish-grey.
PHYSICAL WEATHERING PROCESSES
Factors Influencing The Physical Weathering
1.Gravitational Force Overburden Pressure, Load And Shearing Stress
2. Expansion Forces Due To Temperature Changes, Crystal Growth Or Animal Activity
3.Water Pressures Controlled By Wetting And Drying Cycles.
They are mostly due to thermal expansion, and pressure release. The repeated action of these
processes cause damage to the rocks
UNLOADING AND EXPANSION: Removal of overlying rock load because of continued erosion
causes vertical pressure release with the result that the upper layers of the rock expand
producing disintegration of rock masses. fractures will develop parallel to the ground surface. In
areas of the curved ground surface, arched fractures tend to produce massivce sheets or
exfoliation slabs of rock. exfoliation sheets resultinf from expansion due to unloading and
pressure release my measure hundreds or even thousands of metres in horizontal extent. large
smooth rounded domes called exfoliation domes to result due to this process
TEMPERATURE CHANGES AND EXPANSION: Various minerals found in the rocks expand at
different rates when the temperature increases. Each one pushes others. When the temperature falls
contraction takes place. because of diurnal temperature changes, the effects are mostly on
superficial layers of the rocks. the effects of this process are significant in hot deserts and cold
deserts. though it is small the continuous process for a longer time and larger area the effect is
greater. The effect is greater at the depth of the rocks. fractures occur parallel to the
surface. due to continuous expansion and contraction, the rock layers become lose and exfoliation
takes place. large dome-shaped structures are formed due to this process. Tores which are
large boulders also form due to this process. exfoliated domes are big in size whereas exfoliated
tores are varied sizes.
FREEZING THAWING AND FROST WEDGING: due to repeated freezing and melting frost
weathering occurs in the pores and cracks of rocks.it is most effective in higher elevations of
the midlatitudes.
48
Glacial areas are subjected to frost wedging daily. In this process, the rate of freezing is more
important. Rapid freezing causes sudden expansion a high pressure. Finally, this process
makes the rock to break into pieces
SALT WEATHERING; salts in the rocks expand due to thermal action hydration and
crystallisation. ex. Calcium sodium magnesium potassium and barium .high temperature between
30 to 50 of surface temperature in deserts favour such salt expansion.
Salt crystals in near-surface pores cause splitting of individual grains within rocks,.which
eventually fall off. This process of falling off of individual grains may result in granular
disingetrationor granular foliation.
Salt crystallisation is most effective of all salt weathering processes, in areas with alternating
wetting and drying conditions salt crystal growth is favoured and the neighbouring grains are
pushed aside. sodium chloride and gypsum crystals in desert areas heave up overlying layers of
materials and with the result, polygonal cracks develop all over the heaved surface. With salt
crystal growth, chalk breaks down most readily followed by limestone, Sandstone, Chalk, Gneiss
And Granite.
BIOLOGICAL WEATHERING: Removal or contribution of ions to the environment due to
biological activity is called biological weathering. burrowing and wedging by an organism like
earthworks termites, rodents help in exposing the new surfaces to chemical attack and assists in
the penetration of moisture and air.
SOME SPECIAL EFFECTS OF WEATHERING: Exfoliation is a is a result but not a process. Removal
of layers from curved surfaces results in rounded surfaces.it occurs due to expansion and
contraction induced by temperature changes. exfoliation domes occur due to unloading whereas tors occur due to thermal expansion.
SIGNIFICANCE OF WEATHERING: Responsible for the formation of soils and erosion and deposition.
biodiversity is basically depending on the depth of weathering .erosion may not be significant when
there is no weathering. weathering aids mass wasting, erosion and reduction of relief and changes in
landforms .weathering of rocks and deposition helps in the enrichment and concentrations of certain
valuable ores of iron manganese, aluminium copper.it is an important process of soil formation.
ENRICHMENT: when rocks undergo weathering some materials are removed through chemical or
physical leaching by groundwater and thereby the concentration of remaining materials increases.
Without such a weathering taking place, the concentration of the same valuable material may not
be sufficient and economically viable to exploit, process and refine, this is what is called
enrichment.
MASS MOVEMENT: these movements transfer the mass of rock debris down the slopes under the
direct influence of gravity. air water ice does not carry debris, but debris carries them. the movements of
mass may range from slow to rapid.
TYPES OF MASS MOVEMENTS: creep, flow, slide and fall. mass movements are active over weathered
slopes than unweathered slopes. mass movements are aided by gravity, not any erosional agent. mass
movements do not come under erosion though there is a shift of material.
When force is greater than resistance mass movement occurs. Ex. Weak unconsolidated material,
thinly bedded rocks, faults, steeply diffing beds, vertical cliffs, steep slopes, abundant precipitation
and torrential rains and scarcity of vegetation.
Activating causes precede mass movements:
(i) removal of support from below to materials above through natural or artificial means
(ii)increase in gradient and height of slopes
(iii)overloading through the addition of materials naturally or by artificial filling
49
(iv) overloading due to heavy rainfall saturation and
lubrication of slope materials
(v)removal of material or load from over the original
slope surfaces.
(vi) the occurrence of earthquakes, explosions or machinery
(vii)excessive natural seepage
(viii)the heavy drawdown of water from lakes, reservoirs
and rivers
(ix)indiscriminate removal of natural vegetation
CLASSIFICATION OF MASS MOVEMENTS
Heave, flow and slide are the three forms of movements the relationship is shown in figure no.
The mass movements can be grouped into three types
1.slow movements 2. Rapid movements 3. Landslide
SLOW MOVEMENTS
CREEP: It generally occurs on moderately steep, soil
covered slopes.
Movement of material is extremely slow. Material may
be rock debris or soil
Ex. Bending of a telephone pole, and fence poles.
50
Types of creep: soil creep, talus creep rock glacier creep
Solifluction: slow downslope flowing soil mass or fine-grained rock debris saturated or lubricated
with water. It is common in moist temperate areas where surface melting of deeply frozen ground
and long-continued rain respectively occur frequently.
MUD FLOW
RAPID MOVEMENTS
CONDITIONS: 1.humid climatic regions
2.gentle to steep slopes 3. Heavy rain 4.
Loose soils
51
EARTH FLOW: movements of water-saturated clayey or silty earth materials down low angle terraces
or hillsides.
EARTHFLOW
In the absence of vegetation cover and
with heavy rainfall, thick layers of
weathered materials get saturated with
water and either slowly or rapidly flow
down along definite channels.it looks
like channels of mud. when they
overflow the channels they engulf the
roads and rail bridges.
They generally occur due to volcanic
eruptions. Volcanic ash dust and other
fragments turn into mud due to heavy
rains and flow down as tongues or
streams of mud causing great
destruction to the human settlements.
DEBRIS AVALANCHES: Found in humid regions with or without vegetation narrow tracks of steep
slopes. It is much faster than mudflow, it is similar
to snow avalanches.
LANDSLIDES: these are rapid and perceptible
movements. dry materials are found .the size and
shape of the materials are depending on the nature
of the rock, degree of weathering, steepness of the slope.
52
SLUMP:
slipping of one or several units of rock debris with a backward rotation concerning the slope
over which the movement takes place
DEBRIS SLIDE: rapid rolling or sliding of earth debris without backward rotation of mass is known as
debris slide.
Debris slide
ROCKFALL
53
Rockslide sliding of individual rock masses down bedding joint or fault surfaces. it generally occurs
at the steep slopes. Superficial layers of the rock generally fall.
54
mass movement
Reasons for landslides along the Himalayas
1. Tectonically active
2. Made of sedimentary rocks
3. Steep slopes
4. Heavy spots of rain
5. Unconsolidated material is found
EROSION AND DEPOSITION
Erosion involves the acquisition and transportation of rock debris
Abrasion by rock debris carried by geomorphic agents also aids erosion
By erosion, relief degrades. the landscape is work down. Weathering may not be pre
condition for erosion.
Weathering, mass wasting, and erosion are degradational processes. It is the erosion largely
responsible for continuous changes that the earth surface is undergoing.
Erosion and transportation are controlled by kinetic energy. the wind running water and glaciers
are controlled by climate.
Comparison of wind running water and glacier
wind Running water glacier
Predominant in hot deserts Found most parts of the earth Found only in high latitude
and altitude
Sand dunes are common
features
Valleys and deltas are
common features
U shaped valleys and
morans are common
Ex. Sahara, Atacama Kalahari Amazon.Nile, Bramhaputra Greenland, Antarctica
Air is gas Water is liquid Glacier is solid
Limited landforms Extensive land forms Limited land forms
High-speed Normal speed Very slow movement
EROSION:‖application of kinetic energy associated with the agent to the surface of the land
along which it moves‖. It is computed as KE =½
M=mass v= velocity KE= kinetic energy
SOIL FORMATION: Soil is the collection of natural bodies on the earth‘s surface containing
living matter and supporting or capable or supporting plants.
Soil is a dynamic material in which many chemical, biological, and physical activities go on
constantly. It is the result of decay, it is also a medium of growth. It is changing and
developing body. Characteristics are changing from season to season.
Too cold, too hot, and dry areas biological activity stops. organic matter increases when
leaves fall and decompose.
PROCESS OF SOIL FORMATION: weathering is a basic process for soil formation. The weathered
material is transported and decomposed due to bacteria lichens and moss. The dead
remains increase the humus of the soil. minor grasses and ferns can grow. Bushes, trees
also grow .plants roots and burrowing animals help the soil formation.
PEDOLOGY: is Science of soil formation
PEDOLOGIST: is the scientist of soil formation
55
SOIL FORMING FACTORS:1. Parent material 2. Topography 3. Climate 4. Biological activity.
5.time
PARENT MATERIAL: passive control factor, it is in situ, onsite, or transported.it depends on
texture, structure, chemical composition of the soil. Nature and depth of weathering is an
important factor. chemical composition, the texture is the characteristics derived from patent
material
TOPOGRAPHY: passive control factor, amount of exposer to the sunlight, drainage
system, steep slopes have less deposition, gentle slopes have thick soils. Plains have thick and
dark coloured soils. In mid-latitude southern slopes expose to the sun light and get
decomposed more.
CLIMATE: it is an active factor in soil formation. Climatic elements are (i) moisture( in terms
of its intensity, frequency and duration of precipitation –evaporation and humidity
(II) Temperature in terms of seasonal and diurnal variation.
Precipitation increases biological activity.
Excess of water helps to transport the dissolved particles to downward
(eluviation)
Deposition of these particles is called ‗Illuviation‘
Heavy rainfall removes the calcium, magnesium, sodium, potassium along with silica.
Removal of silica is called desilication
In dry areas excess of evaporation leads to deposition of salts on the surface of the soil
These salt layers are called ‗hard pans‘ in the hot deserts
In tropical climates, under moderate rainfall conditions, calcium carbonate nodules are formed.
Biological activity: plants and animals add organic matter to the soil. also helps in moisture
retention. Dead plants add humus to the soil In humid areas, the bacterial activity is
higher than cold areas
As a result, undecomposed material is found in cold areas
In hot areas, bacteria fix the nitrogen in the soil which is used by the plants
Rhizobium is the bacteria fix the nitrogen in the soil and live in the roots of legumenace
plants ants, termites, rodents, earthworms change the chemical composition of the soil.
Time: Important controlling factor of soil formation.Longer the time, thicker the soil layers. No
the time limit for the formation of the soil layers.