This article deals with ‘Plains.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Introduction
Plain is an extensive tract of
flat and or a gently undulating terrain without prominent hills or
depressions.
They are formed both by
internal forces of the Earth and by external processes of aggradation and
degradation.
They range in size from very
small to a very large areas.
The great centres
of population of the world are on plains. Development of means of
communications and transportation facilities is easier in the plains. Hence, these are
best known areas for human habitation.
Types of Plains
Plains are best classified according to their origin
1 . Diastrophic Plains
Plains formed on regions that
were once submerged under ocean or sea.
Example : Great plains of
U.S.A which extend till Canada were
formed due to upliftment submerged landmasses under epicontinental
seas and were uplifted at the end of Cretaceous period to due tectonic
movements . They have deposits of horizontal thick beds of Marine
sediments
2. Peneplains
Undulating surface of low relief, interspersed with
occasional residual hills and claimed to have been formed due to erosion
by rivers and rain.
Example include East Central
Africa
3. Flood Plains
Flood Plain is that part of
river valley adjacent to the channel, over which a river flows in times of
floods.
Floodplain is composed of
Alluvium
Examples : Indo-Gangetic plain
and the plains of Mississippi, Amazon, Nile, Hwang-Ho, Yangtze Ob, , Lena,
Volga rivers
4. Delta Plains
As rivers draw near seas to
disappear in them, their flow goes dead slow. It necessities the waters to
deposit all types of materials being carried by it. Such depositions are
made in triangular shape which resembles to Greek word ‘Delta’.
These plains are the most
fertile plains of the world.
Examples : Sundarbans of Ganga
and Brahmaputra, Deltas of Nile and Mississippi etc.
5. Aeolian Plains
Aeolian plains are plains formed by either erosive or depositional action of winds
Examples
Sahara and Thar
Plains formed by filling of lakes in Kashmir and Manitoba (Canada)
Lava plains of Idaho (U.S.A.)
Plains of Mecca & Medina
Importance of Plains
Plains are the ‘cradles of
civilizations’ and the ‘food baskets’ of the world with 80% of population
living in plains, i.e., Prairies (U.S.A), Steppes, Pustaz (Europe), Veld
(South Africa), Great Indo-Gangetic Plains of India, Downs (Australia),
Canterbury plains of New Zealand
Undulating and fertile land of
plains is beneficial for conducting agricultural activities and irrigation
Developing means of transport
like building roads, lying railways, preparing air strips etc. is easy in plains.
Industry and other commercial
activities are more easy to be carried out in plains.
This article deals with ‘Plateaus.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Introduction
Plateau is an elevated tract of
relatively flat land , limited on atleast one side by steep slope falling abruptly
Eg: Tibetan plateau.
Reasons for formation of Plateaus
There are many reasons for the formation of Plateaus
When two mountain ranges are
forming, then landmass in between them rise too & Plateaus are formed .
Deposition from lava – if lava is basaltic it will spread easily & form flat elevated surface
Deposition from wind over long time
=> After compression & solidification of deposited
material plateau will form.
When upland of any surface is
eroded due to glaciers, plateau is formed.
Types of Plateaus
1 . Intermontane plateau
Intermontane plateaus are highest, largest & most complex plateaus of world.
Intermontane plateaus are enclosed and surrounded by mountain ranges from different sides.
Examples include
a. Tibetan Plateau
Stretches 1000 km north to
south & 2500 km east to west
& average elevation is 4500m => called Roof of the
world .
Bounded
by Kunlun Mountains in the north & Himalayas
in the south.
Many major rivers
of Asia like Indus, Brahmaputra etc rise here & also holds
constellation of salt & freshwater lakes .
b. Plateau of Bolivia
Lies largely in Bolivia
It has average elevation
of 1350 m.
Highland was uplifted during tertiary period when
the Andes were formed
Contrary to Tibetan Plateau,
it is very dry and has no exterior
drainage
c. Plateau of Mexico
Plateau stands between the
eastern and western Sierra Madre Mountains.
It has average elevation
between 1800 meters to 2300 meters
Large parts of this Plateau are very dry.
d. Colorado Plateau
Situated in USA between
Cascade Range and Rocky Mountains
It is situated at elevation
e. Anatolia Plateau
Lies in Turkey between Taurus
& Pontic Range
It’s elevation is
cause of cool weather of Turkey
2. Piedmont or Border Plateau
These Plateaus border mountain ranges and owe
their present position to the same uplifts that raised the mountains.
Examples include
Piedmont Plateau on the
border of Appalachian Mountains
Patagonia Plateau in South
America
3. Volcanic Plateau
Volcanoes form variety of
plateaus.
Larger : built by BASALTIC lava flow.
Small : formed by resistant
lava caps that aren’t eroded & maintain its elevation after
surrounding land has been worn away.
Examples are
Columbia Snake Plateau .
Deccan Plateau , India.
Shan Plateau , Myanmar
Katanga Plateau, Congo
North Island
in New Zealand
4. Erosional Plateau
Form in semiarid regions where
streams have cut away portions of high lands.
Examples include
Allegany Plateau near New York
Cumberland Plateau near
Appalachians in USA
5. Depositional Plateau
Formed due to depositional
action of wind
Examples include Loess Plateau in China => It is formed due to process of deposition
of sediments carried from the desert
by the Anticyclonic winds
which develop over Russia and come to China shedding their load in this
area
6. Dome Plateau
These plateaus are uplifted by
folding and faulting processes into
a broad dome.
Entrenched Meanders are
feature of these plateaus
Examples include Ozark Plateau
of USA
7. Glacial Plateau
These are formed
due to erosional action of
glaciers.
Examples include
Laurentian Plateau of Canada
(North America)
Garhwal Plateau of India
Importance of Plateaus
Plateaus have large amount
of mineral wealth like Gold, Iron,
Copper, Diamond, Manganese, Mica , Granite etc. which forms industrial
base of any economy. Eg : Katanga Plateau of Congo is very rich in copper
and Deccan Plateau of India is very rich in resources.
Plateaus are have more plain
regions as compared to pure mountainous regions which helps in development
of means of transport. Rail and road transport is lesser costly in plateau
regions as compared to mountainous regions.
Plateau regions have abrupt
slopes which are beneficial for setting up hydroelectrical centres thus
helping in overall development of the region
Plateaus greatly effect the
climate of region . For example Tibet plateau divides western Jet Stream
in two parts while in summer and helps to create low pressure over Indian
subcontinent which results into attraction for Monsoons
They are important
agriculturally as well . Eg : Deccan Plateau in India has black soil which
is unmatchable for production of Cotton and Sugarcane.
Plateaus especially
Intermontane Plateaus are great source of water resources as well. Eg:
Large number of rivers like Indus , Brahmaputra etc originates from Tibet
plateau.
This article deals with ‘Mountains.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Folding and Faulting
Process of mountain formation involves concepts of Folding and Faulting. Hence, we will first learn about these concepts.
1 . Folding
Folding is the bending of
rock strata due to compression.
Folding on a large
scale results in mountain building referred to as orogeny
Up thrown part of a fold is
called anticline. Down thrown part of a fold
is syncline. The side of the fold is a limb
Types of folding
Symmetrical fold
When compressional force is equal from both sides, the angle of the limb is same on both sides.
Asymmetrical
fold
When compressional force is more from one end, one limb is steeper than the other.
Isoclinal
folds
similar
to symmetrical folds, but these folds both have the same angle and are
parallel to each other
Over
turned fold
When one
limb of the fold is pushed over the other limb of the fold, it is called as
over turned fold.
Recumbent
fold
When one
side of the fold is pushed so much that it lies positioned over the other
2. Faulting
A fault is a break in earth’s crust where blocks of rock crust slide past each other.
Types of Faults
2.1 Normal Fault
Vertical displacement of the
crust is called a normal fault.
Normal fault is caused by
tensional forces where plates diverge.
One block lies above and other block lies below the fault
Landforms made by Normal fault are:
Rift Valley or Graben : When a narrow block of land drops or subsides between two parallel normal faults, rift valley (Graben) is formed. Eg : River Rhine Rift valley between Black Forest and Vosges, Narmada Rift Valley between Satpura and Vindhya and Great African Rift Valley
Horst : When a block of land between two faults is pushed up, block mountain or horst is formed. In this case, the central block is not only up thrown but the side blocks are also relatively downthrown . Eg : Mountains Vindhya and Satpura.
2.2. Reverse Fault
Reverse fault is a horizontal displacement of the crust.
It is caused by compressional forces
2.3 Shear Fault
It is
created by shearing along transform boundaries. Rocks on either side of fault
slip past each other sideways with little up or down motion
Classification of Mountain Ranges of the world
Mountains can be categorised in different ways
1 . Classification of Mountains on the basis of height
2. Classification on basis of location
3. On basis of period of formation
We
have to note the fact that Mountains are born &
have finite life span like
Young
mountains
High,
steep & growing upward (like
Himalayas and other Alpine mountains).
Middle
aged mountains
Cut by erosion
Old
mountains
Deeply eroded & often buried (like Aravalli, Appalachians etc)
Types of Mountains on basis of formation
Based on difference in process of their formation, there are following types of mountains :-
Fold Mountains
Bock Mountains
Volcanic Mountains
Domed Mountains
1 . Fold Mountains
Folded mountains are formed due to folding of crustal rocks by compressive forces generated by the convergence of tectonic plates. Eg :
Convergence of Indo-Australian
and Eurasian plate leads to the formation of Himalayas.
Convergence of American and
Pacific plate leads to formation of Rockies
Convergence of South American
and Nazca plate leads to formation Andes
Process of their formation is known as Orogeny. It is not a continuously happening process in the geological past but it happens intermittently. In whole of the geological past, total 9 Orogenies have happened of which last four are important for us
Pre-Cambrian
Orogeny ( Laurentian , Algoma etc)
Caledonian (Aravallis,
Appalachian etc )
Hercynian Orogeny
(mountains include Mountains of Iberian Peninsula, Spanish Messeta
etc )
Alpine Orogeny (they are the
youngest and are still rising. Mountains include Andes, Rockies,
Himalayas, Alps, Atlas etc)
Characteristics of Fold Mountains
Extensive mountain chain
spread over large area .
They are of great height .
Formed along unstable parts of
earth and plates are active there . Hence, earthquakes are quite common in
this region.
Sedimentary
deposits of marine origin are also found in this .
Fold Mountains also have age –
Himalayas are one of the youngest ranges & that is why they are so high .
Aravalli is one of oldest mountain range . After million of years Aravalli is still standing , this vouches for its great heights during youthful stage ( which might be even higher than Himalayas )
Side Topic : Phases in formation of Mountain Ranges
1st Stage : Oceanic-Continental Collision
Convergence of Ocean &
Continental Plate.
This will lead to formation of
mountains on the Continent-Ocean margin.
Examples include Andes
Mountain at convergence of Nazca and South American plate.
2nd Stage : Development of Geo-Syncline
This is developed between
Mountains & Trench .
In this , sediments from
river as well as from ocean keep on accumulating
And geo-syncline is formed
3rd Stage : Continental -Continental Collision
Ultimately whole of ocean plate will be subsumed .
Then continental continental plates will collide and compressive forces cause folding of Continental Crust along with squeezing and folding of sediments and material at the Geo-Syncline (reason why Marine Sediments are found in Fold mountains)
2. Block Mountains
Block mountains
are formed due to faulting in the ground surface. In this case, the
central block is not only up thrown but the side blocks are also
relatively downthrown
Block Mountains represent the Horst with Rift valley or Graben on either sides.
Examples include
Sierra Nevada mountains of California (USA)
Salt range of Pakistan,
Rhine rift valley in Europe
Vindhya and Satpura in India
3. Volcanic Mountains
Volcanic Mountains are formed
due to Volcanic Activities
Examples include Mount
Kilimanjaro in Africa, Mount Fujiyama etc
They are formed
with the consolidation of Andesitic
magma coming out of earth’s crust
4. Upwarped (domed) Mountains
Formed by upwarding of surface due to pressure on
crust from below
Example : Adirondack
mountains of New York.
Side Topic : Isostasy
It is seen that heavily snow covered glacial regions
in the Polar belts (eg Norway, Greenland) tend to rise up over long period with
the melting of the snow (rebound). Why?
Isostasy
is the phenomenon of rebound of the earth’s crust in regions where elevation is reduced
due to degradation and relative erosive processes. Here , the rebound
compensates reduction in height
Since,
Tectonic Plate is floating on Asthenosphere , when mountain is eroded or snow
melts there is lowering of mass and hence rebounding of the tectonic plate
upwards happen
Importance of Mountains
Mountains
cover 27% of earth’s continents and 20% of population resides here making
it an important part of human civilization
Mountains are great source of
resources like Hydroelectricity, Wood, Medicinal plants, wild
animals/insects, fruits etc.
Most of the perennial rivers
of the world originate in mountains like Ganga, Brahmaputra, Rhine, Hwang
Ho , etc. Human civilizations were
made possible by the rivers originating in mountains since most of the old
civilizations like Indus valley civilization, Mesopotamian Civilisation
(Euphrates) , Egyptian Civilization (Nile) etc flourished on the banks of
these rivers
Mountains are source of
attraction for tourism related activities. Large number of people visit
mountainous regions as tourists and also helps in generation of employment
in those regions.
They have religious and
cultural significance as well. For example, Himalayas are abode to many
Hindu gods like Shiva.
Mountains have their lasting
effect over climate of any region. In India, the Himalayas contribute very
importantly for rainfall not only through Monsoon winds but through
cyclones also.
This article deals with ‘Continental Drift and Plate Tectonic Theory.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Continental Drift Theory
Given by Alfred Wegener (German Meteorologist) in
1912 . It speaks about
rifting and drifting of continents .
According to Wegener, about 250 million years ago all the
continents formed a single continental mass and mega ocean surrounded the same.
Super continent was named PANGAEA, which meant all earth.
Mega-ocean was called PANTHALASSA, meaning all water.
He argued that, around 200 million years ago, the super continent, Pangaea, began to split.
Pangaea broke to Laurasia/ Angaraland (forming Northern Continents) and Gondwanaland (Southern Continents) with Tethys Sea between them.
Subsequently, Laurasia and Gondwanaland continued to break into various smaller continents that exist today. (Note – India was part of Gondwanaland.)
Interesting
theory but was scrapped saying it GEO-POETRY because he wasn’t able to
explain forces of movement.
Continental Drift theory was based on following clues
a. Continental fit / Jig Saw Fit
Continental lands can be joined together like jig saw puzzle.
b. Rocks of same age across oceans
Belt of ancient rocks of 2,000
million years from Brazil coast matches
with western Africa.
Geological Structure of
Appalachian Mountains matches with Morocco and Algeria in North Africa.
c. Fossils
Mesosaurus
Freshwater
reptile found in Africa & South America.
Glassopteris
Fern found on all southern
continents.
Lemur
Found in
India, Africa and Madagascar.
d. Placer Deposits
The occurrence of rich placer deposits of gold in the Ghana coast and the absolute absence of source rock in the region => gold bearing veins are in Brazil => Ghana & Brazil Plateau used to lay side by side.
e. Tillite
Tillite are the sedimentary rock formed out of deposits of glaciers.
Gondwana system of sediments from India has counter parts in six different landmasses of Southern Hemisphere.
Forces for Drifting
Wegener suggested that
movement responsible for drifting of continents was caused by pole-fleeing force and tidal force.
Polar-fleeing force relates to
the rotation of the earth.
Tidal force—is due to the attraction of the moon and the sun that develops tides in
oceanic waters.
Wegener believed that these
forces would become effective
when applied over many million years. However, most of scholars considered these forces to be
inadequate
Post Drift Studies
It is interesting to note that
for continental drift, most of the evidences were collected from the
continental areas .
Number of discoveries during
the post-war period added new information to geological literature.
Particularly, the information collected from the ocean floor mapping
provided new dimensions for the study of distribution of oceans and
continents.
Convectional Current Theory
Wegener wasn’t able to explain
the force behind Continental Drift.
Arthur Holmes in 1930s discussed the possibility of convection
currents operating in the mantle portion. These currents are generated due to radioactive
elements causing thermal differences in the mantle portion. Holmes argued that
there exists a system of such currents in the entire mantle portion.
These convection currents are
nothing but molten rocks
Rising limb : it
will pressurise crust in such a way that crust will break .
Diverging limbs : take crust away from each other .
Descending limbs : make two crusts to collide
(like Indian & Eurasian plate ).
According to Holmes
, these Convection
Currents are the Driving Force . This was an attempt to provide an explanation
to the issue of force, on the basis of which contemporary scientists
discarded the continental drift theory.
Ocean Seafloor Spreading Theory
Post war studies using which Ocean Map was prepared showed that ocean floor is not just a vast plain but it is full of relief.
Mapping of the ocean floor and palaeo-magnetic studies of rocks from oceanic regions revealed the following facts :
It was realised that all along
the mid-oceanic
ridges, volcanic eruptions are common and they bring
huge amounts of lava
Ocean crust rocks are much
younger than the continental rocks. The age of rocks in the oceanic crust is nowhere more than 200 million
years old. Some
of the continental rock formations are as old as 3,200 million years.
Age of
the rocks increases as one moves away from
crest.
Sediments on the ocean
floor are unexpectedly very thin => nowhere was sediment
column found be older than 200 million
years.
Deep trenches have deep
earthquake occurrences while in mid-oceanic ridge areas, earthquake foci
have shallow depths
Concept of zebra strip / Magnetostratigraphy : rocks equidistant on either
sides of mid-oceanic ridges show
similar magnetic properties
This led Hess (1961) to propose his hypothesis, known as the “sea floor spreading”
Constant eruptions at crest of oceanic ridges cause rupture of the oceanic crust and new lava wedges into it, pushing the
oceanic crust on either side. The ocean floor, thus spreads.
Ocean floor that gets pushed due to volcanic
eruptions at crest, sinks down at the oceanic trenches & gets
consumed (Seafloor Spreading Theory).
Plate Tectonic Theory
Given in 1967 by McKenzie & Parker
Tectonic plate ( lithospheric
plate) is a
massive slab of solid rock, generally composed of both continental and
oceanic lithosphere. Plates move horizontally over the asthenosphere . Its
thickness range varying between 5-100 km in oceanic parts and about 200 km
in the continental areas.
A plate may be referred to as
the continental plate or oceanic plate depending on which of the two
occupy a larger portion
Pacific plate is largely an oceanic plate
Eurasian plate may be called a continental plate.
Theory of plate tectonics proposes that the
earth’s lithosphere is divided into seven
major and some minor plates.
Young Fold Mountain ridges,
trenches etc are formed due to movement and interaction of these plates
The major plates are
Antarctic and the surrounding
oceanic plate
North American
South American
Pacific plate.
India-Australia-New Zealand
plate .
Africa with the eastern
Atlantic floor plate .
Eurasia and the adjacent
oceanic plate.
Some important minor plates are
Cocos plate : Between Central
America and Pacific plate .
Nazca plate :Between South
America and Pacific plate .
Arabian plate : Mostly the
Saudi Arabian landmass.
Philippine plate : Between the
Asiatic and Pacific Plate .
Caroline plate : Between the
Philippine and Indian plate (North of New Guinea) .
Fuji plate : North-east of
Australia.
2017 update – Zealandia is now
considered separate Continent/Plate
These plates have been constantly moving over the globe throughout the history of the earth.
All the plates, without
exception, have moved in the geological past, and shall continue to move
in the future as well.
Pangaea of Wegner was also
result of convergence of continental masses
Plate Boundaries
There are three
types of plate boundaries according to Plate Tectonic Theory (these three types
of plate boundaries are discussed in detail below)
Rate of Plate Movement
Strips of normal and reverse
magnetic field that parallel the mid-oceanic ridges help the scientists to
determine the rates of plate movement.
These rates vary considerably.
Arctic Ridge: slowest rate
(less than 2.5 cm/yr),
East Pacific Rise in the
South Pacific : fastest rate (more than 15 cm/yr).
Force for the Plate Movement
Convectional Currents which
were first explained by Hess in his Convectional Current Theory was the
main force behind plate movement
Side Topic : Palaeomagnetism & how it prove Plate Tectonics
Palaeomagnetism
is the study of the record of the Earth’s magnetic field in rocks and sediments
How it proves Plate Tectonic Theory
Magnetostratigraphy, with rocks equidistant on either sides of
mid-oceanic ridges show similar
magnetic properties
Polar wandering – Magnetic minerals formed at
same time but on different continents points have different orientation
. So, there were either multiple
north poles during the same time period or that the continents moved in
relation to a single north pole. Geophysicists concluded that the magnetic
poles remained stationary, and the continents moved
Palaeomagnetism is also used
to match once joined landmasses that are now separated. For
example, the orientation of magnetic minerals along the eastern coast of
South America very closely matches that of similar minerals on the western
coast of Africa.
Convergent Plate Boundaries
Convergent plate boundary is the margin where two plates collide with one another.
Convergent Plate Boundaries can be of three types :-
1 . Ocean Ocean Convergent Boundary
Denser of the two oceanic
plates is subducted . It goes to
Asthenosphere & generate new Magma .
Andesitic
Magma will from in this case . Andesitic Magma is less mobile and solidifies quickly. As a
result, underwater Volcano or Volcanic
island arc will form in this case.
Characterised by Trenches
, Underwater Volcanoes , Volcanic Island Arc and Earthquakes .
Island arc (and not single island) will be formed
because they will be formed on whole boundary where Ocean-Ocean plate is
converging. All these islands will be volcanic islands .
2. Ocean – Continental Convergence Boundary
Oceanic Plate is
denser than Continental Plate . Hence, Ocean plate will be subducted into
Asthenosphere & melt down
there. But at the same time, due to the great compressional force between
two converging plates, folding will happen on the Continental Plate , resulting
in formation of Marginal Fold Mountains . As we know, folding happens
along the zones of weakness ,
hence, when Magma of the subducted
Ocean plate will rise , it will
come out of the crust through these weak zones resulting in formation of Volcanic Peaks
.
Hence, Volcanic mountains ranges, Trench and earthquakes are common on boundaries
Examples of such volcanic
mountain ranges are
Andes mountains
South
America
Rockies
North
America
Atlas
Africa
3. Continental – Continental Convergent Boundary
When continental plate converges into continental plate , crust at both sides is tool light & buoyant to be subducted. Both are compressed against each other and folding happens. Hence, in this case Fold mountain Belt forms.
No Volcanism but powerful earthquakes are created in this region .
Himalayas & Urals are formed in this way due to convergence of Indo-Australian and Eurasian plates.
Pressure between plates is so high that metamorphic rocks form there.
Divergent plate Boundaries
Divergent plate boundary is
the margin where two plates move apart. For instance, African plate and
South American plate
Divergent plate boundary is
termed as the
constructive plate boundary as it leads to the formation of new lithosphere .
Divergent plate boundaries are of two types :-
1 . Ocean – Ocean Divergent Boundary
Creation of new
crust takes
place at submarine mountain ridge . Ocean crust is rifted apart & basaltic magma wells up to
fill the opening.
Basaltic Magma will
come out from the Mantle. Since basaltic magma is very mobile, hence it will spread
out. This magma hardens & forms igneous rock . Since magma is basaltic, hence ocean crust
is basaltic in nature .
Mid-Atlantic Ridge is an ideal example of a submarine mountain ridge in the Atlantic Ocean. It is the longest mountain ridge in the world. It extends for about 16,000 km, in a ‘S’ shaped path, between Iceland in the north and Bouvet Island in the south
Water from hydrothermal vents (along the submarine ridges) is rich in dissolved minerals and supports organisms like chemo-autotrophic bacteria.
2 . Continental – Continental Divergent Plate
Rift valley along with block mountains are formed when two continental plates move apart.
Initially it leads to the development of a small body of water . But if rifting continues , body of water becomes bigger to juvenile ocean and consequently to Large Ocean.
Example : The Great Rift of Africa
Side Topic : Great Rift of Africa
In Great African Rift Valley,
Continental Continental Divergence is observed leading to formation of
Rift Valley.
Almost all the
lakes in Africa are in the Rift Valley generated by diverging of continental Plates except Lake
Victoria.
Transform Plate Boundary
Where two plates are sliding past each other.
They are under shear stress.
The lithosphere is neither destroyed nor created by the transform plate boundary. Hence , it is called Conservative or passive plate boundary.
Earthquakes are common & Volcanoes are not formed at Transform boundaries. Whenever plate boundary is active, Earthquakes are also experienced in that region.
Example –San Andreas Fault in USA (Pacific Plate & North American) , Chile etc
This article deals with ‘Earthquakes .’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Introduction
Sudden release of energy in Earth’s crust, which leads to series of motions due to waves created by the released energy is called Earthquake. Hence , it is nothing but release of energy.
Terminology
Hypocentre/
Focus
Point
inside surface where earthquake is generated by first rock displacement &
fault is created.
Epicentre
Point on earths surface
which is directly above hypocentre.
Most destruction occurs
here.
Earthquakes occur in three forms of clusters
Foreshocks
Occur
before a larger one at same location.
Mainshocks
Are of
highest magnitude & occur within an hour of foreshock.
Aftershocks
Are
smaller quakes that occur at same general geographic location for days &
even years after the larger main shock
Types of Earthquake
1 . Types based on causes
a. Tectonic Earthquake
Most common type are the
tectonic earthquakes.
These are generated due to
sliding of rocks along a fault plane.
b. Volcanic Earthquake
Due to volcanic eruption.
But confined to areas having active volcanoes .
c. Collapse Earthquakes
In the areas of intense mining activity, sometimes the roofs of underground mines collapse causing minor tremors.
d. Explosion Earthquake
Ground shaking may also occur due to the explosion of chemical or nuclear devices.
e. Human Induced Earthquake
Earthquakes that occur due to human activities
Reservoir induced seismicity
Mining related seismicity
Groundwater extraction related earthquake
Types on basis of depth
a. Shallow focus
Hypocentre is upto 70 km
Not felt
away from epicentre
Cause maximum destruction in
the region near epicentre (energy released is close to surface)
b. Medium focus
Hypocentre is from 70 to 300 km
Distance of impact and
destruction potential between deep focus and shallow focus.
c. Deep Focus
Hypocentre is below 300 km
Felt upto large distance from
epicentre
Cause low destruction
Side Topic : Why maximum destruction is near the epicentre?
As one
moves away from the epicentre, wavelength of surface wave will increase. Hence,
building situated near the epicentre will fall on both crest and trough of wave
causing building to collapse while building situated away from the epicentre
will either fall entirely on crest or trough not doing much damage.
Effects of Earthquake
Earthquake
is a natural hazard. The following are the immediate hazardous effects of
earthquake:
Ground Shaking
Land and mud slides.
Soil liquefaction.
Ground lurching .
Avalanches.
Ground displacement
Floods from dam and levee failures .
Fires.
Structural collapse.
Falling objects
Tsunami.
Change in course of river
Human and property loss
Cracks in building
Earthquake Belts in World
Three major earthquake belts in this world :-
a. Circum-Pacific Belt
Along a patch surrounding the Pacific ocean
Region of great
seismic activity eg Japan, Philippines, Chile etc lies here
Coincides with Pacific Ring
of Fire.
b. Alpine Himalayan Belt
Runs through
mountainous region that flank Mediterranean Sea extend through Iran &
Himalayan mountains
Frequent & destructive
earthquakes occur here.
c. Other areas
Northern Africa
Rift Valley areas of the Red
Sea and the Dead Sea.
Earthquakes In India
India has high frequency of great earthquakes (greater than 8.0) .
Reason
Tectonic setting of India .
Indian plate is moving at a
speed of one cm/ year towards
the north & north-eastern direction and this movement of plates is being
constantly obstructed by the Eurasian plate from the north. As a result of
this, both the plates are said to be locked with each other resulting in accumulation of energy . Excessive accumulation of energy results
in building up of stress, which ultimately leads to the breaking up of the
lock & sudden release of energy causing earthquake
Region has remained seismically quiet for more than
600-700 years => enormous buildup of strain => Earthquake of magnitude
8.5 or more can hit region in near future
Some Great Earthquakes occurred in India.
1819:Gujarat
8.3
1897:Assam
8.7
Extensive
liquefaction in alleviated plains of Brahmaputra.
1934:Bihar-Nepal
8.4
Extensive
liquefaction —-> buildings tilted & slumped bodily into ground.
1967:Koyna
6.5
– 1962 —-> Koyna Dam built —> earlier area was aseismic but after this seismic activity increased—-> dam induced earthquake – Revision of Indian Seismic was done and in Zone map, Koyana was moved from Zone I to zone IV & Bombay to Zone III.
Question : What are the reasons for occurrence of earthquakes in geologically inactive regions like Peninsular India ?
It is possible that collision of
Indian and Eurasian plate has generated stresses not only at boundaries
but also inside plate. As a result zones of weakness have formed on the plate. There is possible breaking up of Indian
plate, which is most evident along
river Bhima near Latur and Osmanabad, regions experiencing disturbances in the past.
Peninsular India is home to some grand dams and reservoirs which have resulted in
reservoir induced earthquakes (eg. Koyna Dam).
Measuring the Earthquake
The earthquake events are
scaled either according to the magnitude or intensity of the
shock.
The magnitude
scale is known as the Richter scale. The magnitude relates to the energy released during the quake. The magnitude is expressed in
absolute numbers, 0-10.
The intensity
scale is named after Mercalli, an Italian seismologist. The intensity
scale takes into account the visible
damage caused by the event. The range of intensity scale is from 1-12.
1 . Richter Scale
Concept of Earthquake
magnitude was developed by Richter who invented Richter scale .
It is Base 10 logarithmic
scale obtained by calculating logarithm of shaking amplitude of largest displacement from zero Anderson
Torsion seismometer at 100 kms from epicenter.
Increase in 1 means 10 times
more shaking amplitude.
Earthquakes with magnitude
more than 6 are destructive
2. Mercalli Scale
Intensity scale is named after Mercalli, an Italian seismologist.
Intensity scale takes into account the visible damage caused by the event.
The range of intensity scale is from 1-12.
Side Topic: Shindo scale
Known as Japanese
Meteorological Agency(JMA) seismic intensity scale.
Used in Japan & Taiwan.
JMA scale tells us about
degree of shaking at a point on earths surface .
Ranges between Shindo 0(no
shaking) to Shindo 7(most
devastating).
Same earthquake has different
Shindo number at different locations.
EARTHQUAKE EARLY WARNING SYSTEM
Earthquake Early warning system will issue warnings 1-40 seconds before earthquakes
Based on detection of waves generated during an earthquake.
P wave is harmless but travels faster than the Surface and S waves which cause maximum destruction
This system works on detection of P wave for advance warning.
This article deals with ‘Oceanography: Ocean Salinity’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you canclick here
Introduction
Salinity of Solution is defined as amount of salt in 1000 gram of water .
Salinity of ocean water is 35.5 ppt ( parts per thousand) & maximum amount is of common salt.
Sodium
chloride
78%
Magnesium
Chloride
12%
Magnesium
sulphate
3.5%
Calcium
Sulphate
2.5%
Why Sodium Chloride (NaCl) is present in highest
proportion ?
Every salt has cycle &
they remain in sea water for specific time( called residual time) &
then precipitated to bottom surface .
Sodium (Na) & Chlorine
(Cl) has highest residual time in ocean water leading to very gradual
removal => that is why they are present in highest proportion .
Salt Budget
Irrespective of absolute
salinity, proportion of above salts
remain same in all parts of the world
.
Amount of addition or
extraction of fresh water compared to salt content in ocean water decides
absolute salinity of oceans .
Salt Budget = Budget of addition of salt &
removal of salt .
Sources of salts on ocean water.
Sediments carried by rivers
(most important) .
Submarine volcanism at Mid
Oceanic Ridge .
Chemical reaction between
rocks of geothermal vent of volcano & cold water.
Erosion of oceanic rocks and
wave erosion of coastal rocks .
Removal of Salts in ocean water.
Physical Removal : waves break at beaches ie salt spray .
Biological removal : marine
life forms extract calcium from sea water for their bones & shells .
Factors effecting salinity
Evaporation
Higher
the rate of evaporation ,higher is salinity.
Temperature
Warmer
parts are more saline than frigid ones.
Precipitation
Higher
the precipitation, lower is the salinity.
Influx of Freshwater
Influx
of freshwater leads to lower salinity .
Atmospheric pressure
Circulation of Ocean water
Stagnant
water has more salinity (Eg: Sargasso sea).
Windy situation
Wind
accelerate evaporation => windy situation = more saline
Salinity of Oceans
Standard salinity of ocean water is 35.5 ppt ie
salinity of Atlantic ocean .
Greater
than 35.5
High
saline.
Lower
than 35.5
Less saline.
Some highly saline lakes .
Man seldom drown in sea with high
salinity because water is highly
dense .
Dead Sea
238 ppt
West
Asia
Lake Van
330 ppt
Turkey
Great
Salt Lake
220 ppt
USA
Lake
Urmia
Iran
Overall pattern of Salinity across world
a. Latitudinal variation
Salinity is highest at tropics(not Equator) & decreases on both sides.
This is due to Interplay of
evaporation & precipitation & other complex interactions.
b. Hemispheric variation
Northern Hemisphere is warmer => high evaporation =>
more saline .
But southern Pacific => Roaring 40, furious 50 , Shreaking 60 , Screaming
70 => very fast winds . Hence in Pacific ocean , southern hemisphere
has more salinity
c. Local Variation in Salinity
Warm
ocean currents
– Increases temperature of water => equivalent to High evaporation . – Leads to more salinity.
Upwelling
Cooler water from depth come to surface => low salinity.
Transport
by currents
The North Sea, in spite of its location in higher latitudes, records higher salinity due to more saline water brought by the North Atlantic Drift.
d. Enclosed Seas
Tropical
region
– Warmer than open sea . – Will lead to high salinity. – Eg Mediterranean Sea , Persian Gulf etc.
High
Latitude
– Cooler than open sea . – Lower salinity than open seas . – Eg Baltic Sea, Gulf of Bothnia etc .
e. Inflow of large rivers
Ganga – Brahmaputra => flow into Bay of Bengal => large freshwater .
Bay of Bengal is less saline than Arabian Sea.
f. Glaciers
Those oceans /seas which receive greater glacier water are less saline
Baltic Sea is very less saline because of this reason .
This article deals with ‘Oceanography: Ocean Temperature’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you canclick here
Introduction
Temperature of ocean water is important because
Life of Phytoplankton & Zooplankton depend on it .
Affects climate of coastal lands .
Points to note :-
Main source of Energy on Earth is sun ie insolation .
Oceans play important role in energy & temperature regulation of earth. Because of its specific heat, water doesn’t get heated & does-not get cold very fast . Hence, water can store energy for very long time .
Average temperature of ocean from surface to bottom is 3-5 Celsius.
But average surface temperature of ocean is 25 Celsius.
Range of temperature
Daily/ Diurnal range of temperature
Difference between maximum
& minimum temperature of a day.
Daily range of temperature is
almost insignificant in case of rivers & is less than 1 degree C at
max
Tropical water has higher
diurnal range than equatorial waters because cooling & heating of
water is rapid under clear sky .
Annual range of temperature
Average is
12 degree C but lot of regional variation.
Higher in case of enclosed
oceans than open seas
Bigger the size lower annual
range of temp because of more mixing .
Distribution pattern of Temperature
Studied in two ways
1 . Horizontal distribution of temperature in oceans
Factors impacting horizontal distribution of temperature in oceans
a. Latitudinal Variation
There is decrease in temperature while going from equator toward poles because of decrease in insolation
But highest temperature is found not at equator but at tropics
Reason : High rainfall & cloud cover at the Equator resulting in High Albedo / reflection of sun-rays by clouds
b. Prevailing Winds
Direction
of the wind affects the distribution of temperature of ocean water.
Off shore winds blowing from
the land towards ocean or sea raise the temperature of ocean water.
Winds blowing from snow
covered regions in winter lower the surface temperature
c. Hemispheric Variation
Waters in Northern Hemisphere warmer than
Southern Hemisphere
. Reason is the oceans in the northern hemisphere receive more heat due to
their contact with larger extent
of land than the
oceans in the southern hemisphere.
Isotherms in north
aren’t regular while in Southern Hemisphere regular.
d. Enclosed Sea
Marginal seas of tropics ( like Mediterranean Sea) are warmer than open Ocean and marginal seas of temperate region (eg Gulf of Bothnia) are cooler than open sea.
Reasons
less mixing of water.
Land heats up surrounding waters too.
e. Ocean Currents
Warm currents
have warming effect on ocean water
Cold currents
have cooling effect on ocean water
f. Upwelling & Downwelling
Upwelling – Brings cool water from depth.
Downwelling – opposite ie warmer .
g. Salinity
If the sea water is more saline, its temperature will be higher because highly saline water contains more energy on the other hand the temperature of less saline water is low.
Horizontal distribution of Ocean Temperature
The average temperature of surface water of the oceans at equator is about 27°C and it gradually decreases
from the equator towards the poles.
The rate of decrease of temperature with
increasing latitude is generally
0.5°C per latitude
The average temperature is
around 22°C at 20° latitudes, 14° C at 40° latitudes and 0° C near poles.
The oceans in the northern hemisphere record relatively higher
temperature than in the southern hemisphere. The average annual temperatures for the
northern and southern hemisphere are around 19° C and 16° C respectively.
This variation is due to the unequal
distribution of land and water in the northern and southern hemispheres.
The highest temperature is not recorded at the
equator but slightly towards north of it.
2. Vertical Distribution of Temperature of Ocean Waters
Maximum temperature is on the
surface because it receives
insolation.
Transmitted to lower sections of ocean by
convection.
Solar rays can
penetrate very effectively till 200m
but seldom go below 1000 m . As a
result, temperature falls very rapidly from 200m till 1000m & after that , rate of decrease of
temperature is very slow (rate & not absolute temperature).
Can be divided into three zones
First layer
Top layer of warm oceanic water & is 200 m thick.
Temperature ranges from 20 to 25degree & no large variation with depth ( almost constant )
Present in tropics throughout year , in mid latitudes in summer & in cold areas never present .
Second layer
Thermocline layer
Below first layer from 200m to
1000 m.
Rapid rate of decrease of temperature to 4 C with increase in depth from 200 m to
1000 m .
Rate of decrease is rapid at
equator & tropics than towards pole because temperature already is
very low in Polar Region
In polar , waters are already at around 4C . Hence, this
layer is not present in polars .
Third layer
Very cold & extend upto
deep ocean floor.
Decrease in temperature with
depth is almost nill.
Polar areas have only this
layer from above till ocean floor.
Ocean Currents, Waves, Tides and Thermo-Haline Circulations
This article deals with ‘Oceanography: Ocean Currents, Waves, Tides and Thermo-Haline Circulations.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you canclick here
Introduction
Major movements of ocean water can be categorised as follows:-
1 . Horizontal Movement : Waves
The waves
are oscillating movements in the ocean water which transfer energy from place
to place.
Creation of waves
Wind pushes (away) the water
body & creates crest.
Gravity pulls the crest
downward & falling water pushes the former troughs upward .
Actual motion of water beneath wave is circular (& not straight) & while we go downward movement of
water molecules keep on decreasing.
Hence, in waves very slow
horizontal movement of water takes
place .
Waves actually involves the transfer of energy and water particles don’t move across the sea/ocean as
such. Water particles only moves in circular pattern as wave passes. Wind
causes waves to travel in ocean and energy is released at the shore.
2 . Horizontal Movement : Currents
Large mass of moving water from one part of the ocean to another in a definite direction is called as ocean current.
The movement is produced due to earth’s rotation, temperature difference of ocean water, salinity, density , air pressure and winds.
They circumnavigate the earth .
What Currents do
Heat re-distribution – from Equator to Poles.
warm water from equator to poles .
cold water from poles to equator.
Factors responsible for ocean current
The primary forces that influence the currents are:–
a. Wind
Most dominated force.
In most cases, direction of
wind will be direction of underlying current .
b. Insolation
Heating by solar energy cause
the water to expand. That is why, near equator the ocean water is about 8 cm
higher in level
than in the middle latitudes.
This causes a very slight gradient and water tends to
flow down the slope.
c. Salinity
Water will move from lower
salinity to higher salinity on the surface .
Reason : Water with higher
salinity being denser sinks & as a result water with low salinity
comes to fill the space.
Eg : Water from
Atlantic flows to Mediterranean
d. Coriolis Force
Coriolis
Effect : Due to rotation of earth – West to East .
Object moving in Northern Hemisphere will deflect Clockwise
Object moving in Southern Hemisphere will deflect Anti Clockwise
Movement of currents should be straight from equator to pole but not straight because
Coastline modifies the path.
Coriolis force
Nomenclature : Warm Current & Cold Current
Warm current is one that carry water
warmer than water found at that latitude .
Water flowing from low
latitude to higher latitude is warm.
Currents effect climate of bordering landmass eg wind blowing to
land from warm current cause rainfall. This is the reason why
mostly east coasts of continents receive rainfall & west coasts are
deserts.
General Pattern of Currents in all Oceans
Due to rotation of earth from west to east , two currents one on each side of equator are formed called North & South Equatorial Current.
Water carried in form of Equatorial currents tend to accumulate in western part of ocean or eastern coast of continent.
To balance this Counter Equatorial Current is formed between two Equatorial Currents from West to East.
Water at eastern coast of continent start piling up & under influence of density gradient start moving towards middle latitudes
At same time high density water at poles start flowing towards equator in form of currents along eastern coast of continent & two meet in middle latitudes where cold water sinks & warm water spreads on it .
The water is pushed towards east by strong westerlies & water reaches eastern part of ocean or western coast of other continent.
Obstruction at western part of continent divides water & one moves toward pole & other toward equator.
The water sinked in middle latitude upwells along the western coast to make good removal of water at equator . As a result circulatory cells known as gyres are formed one in each major ocean basin & is situated between 20 to 30 degree in both hemisphere.
This system is found in all oceans except Indian ocean where major changes occur due to presence of Indian peninsula & seasonal reversal of winds producing double gyre moving in seasonally opposite directions.
2.1 Currents in Atlantic Ocean
Warm Currents in Atlantic Ocean
a. North Equatorial Current
North equatorial current flows
from east to west between 5– 20 N latitudes.
After leaving the west coast
of Africa, it attains its main characteristics.
When it reaches the east coast
of South America, it splits into two branches and one branch called
Antilles current moves along the coast of West Indies and other branch is
diverted into the Caribbean sea.
b. South Equatorial current
It flows south of equator within 0 – 12 S
latitude in between the coast of Africa and South America.
It is stronger than the North
equatorial ocean current
c. Gulf Stream
Gulf Stream starts from the
Gulf of Mexico and carries warm waters into the colder latitudes.
It bends with the coastline up
to 40th parallel after which the direction is almost to the east, due to
the force and the direction of the westerlies and the deflective force of
the earth.
It joins the Labrador cold
current near New Found land, Canada
making it a good fishing ground.
d. Brazil Current
Warm current moving south
along the coast of Brazil.
It joins the Falkland cold
current near Bahia Blanca making it
a good fishing ground.
e. Norwegian Current /North Atlantic Drift
Norwegian Current takes warm water towards the coast of Norway allowing it’s coast to be operational throughout the year.
Cold Currents of Atlantic Ocean
a. Canary Island
It flows south along the Western coast of North Africa
between Maderia and Cape verde
Gradually , it merges with the
North equatorial current.
b. Labrador Current
In the north Atlantic, it
flows from the Baffin Bay and Davis Strait towards south.
It brings cold waters from polar zone and
moves along the coast of green land.
It meets with warm Gulf Stream
near New Found Land making it a good fishing ground.
c. Benguela Current
It flows northward along the
western coast of Africa
It carries cold waters from
sub-Antarctica surface water and mixes with south equatorial current
Side note : Newfound Land Island
Meeting point of Gulf Stream( warm current) & Labrador current (cold Current)
Amount of planktons increases resulting in large number of fishes. Hence, it is Good fishing ground.
Side Note: North Atlantic Drift / Norwegian Current
It provides warming effect to
western Europe.
Due to this, ports of Norway
– Narvik, Hammerfest , Murmansk etc keep on operating in
winter but at same latitude ports in Russia freeze during winter .
Side Note : Canary Current and Sahara Desert
Canary current is cold
current(passes near Canary Islands).
They give desiccating effect
(drying effect) to Sahara Desert resulting in no rainfall .
Side Note : Sargasso Sea
It is the only sea in the world without a land boundary. Its boundaries are defined only by ocean
currents. It is encircled by the Gulf
Stream in the west, north Atlantic drift in the north, Canary current in
the east and North Equatorial and Antilles current in the south
Due to confinement , Sargassum ie a sea weed grow in this region which obstructs
navigation. Plants have become adapted to life in the open sea, need no
roots or holdfasts for attachment, and are able to propagate by breaking
off bits to grow into new plants through vegetative propagation.
It is very saline. Reasons for this are
Prevention of mixing of fresh
water from surrounding oceans due to virtual boundary created by the
ocean currents.
High Evaporation due to high
temperature owing to its subtropical location
Gulf Stream brings in high
salinity water to the sea.
It is devoid of nutrients
& hence, poor marine life .
Side Note : Bahia Blanca & Falkland Island
Meeting point of warm Brazilian & cold Falkland Current .
Important for fishing
activity.
Side Note : Benguela Current & Namib Desert
Benguela Current is a Cold Current.
It gives desiccating effect leading to low rainfall on the south-west coast of Africa and formation of Namib Desert.
2.2 Currents of Pacific Current
Cold Currents of Pacific Ocean
a. Oyashio current
It originates from the Bering
Strait and flows towards south carrying cold water.
It meets with Kuroshio warm
current
b. California Current
Californian current is flowing
towards south along the west coast of U.S.A between 48 N and 23 N
latitudes.
Has desiccating effect which
leads to formation of Mohave and Sonoran desert.
c. Peru Current
Peru Current is the best
studied ocean current of the Pacific Ocean.
Alexander Von Humboldt in 1802
noted the details of the Peru Current. Hence, it is also known as Humboldt
Current.
It flows north along the west
coast of South America carrying cold water
d. Alaska Current
Cold current originating near Alaska and flowing south to meet North Pacific Current
e. West Wind Drift
It is an easterly moving drift
in the Pacific Ocean extending from Tasmania to the South American coast.
It is a cold current.
The speed of the drift is
greater under the influence of Roaring Forties.
Warm Currents of Pacific Ocean
a. North Equatorial Current
North equatorial current
originates from Revilla Gigedo island west of Mexico due to trade winds
and flows towards the Philippines Island covering a distance of about
12,000 km
It gets divided into two and
the northern branch joins the Kuroshio Current and the southern branch
abruptly turns and forms the Pacific counter current.
b. South Equatorial Current
South equatorial current is
originated due the action of the trade winds from east to west
It is stronger than the North
equatorial current.
It is further divided into
many branches due to the presence of many islands and uneven surface
topography.
c. Kuroshio Current
Warm ocean current flowing in
north easterly direction up to 30 N latitude
It meets Oyashio cold current
off the Kuril Islands.
d. East Australian Current
Warm current flowing southward along the east coast of Australia
Side Note : Japan is good Fishing Ground
Warm Kuroshio Current & cold Oyashio Current meets near Southern Japan. Hence, it becomes rich fishing ground.
Along with that Japan has very shallow continental Shelf leading to more photic zone and more marine organisms.
Indented coastline of Japan leads to formation of natural harbors .
Furthermore, Japan is a hilly region with less developed agriculture . Hence, there is main role of fishes in Japanese Diet.
Side Note : Peru Current and Atacama Desert
Peru / Humboldt current is cold current. Hence, it provides desiccating effect to the South American coast leading to formation of Atacama Dessert . Atacama desert is one of the driest places on Earth.
Current Topic : Pacific Garbage Patch
Pacific Ocean Garbage Patch is an enormous collection of marine debris (mainly plastic) that is collected and deposited by ocean currents in the middle of the North Pacific Ocean.
Reasons of
formation
Geographical
: Circular motion of the ocean currents draws debris into the center which is calm &
stable, where it becomes trapped.
Almost 80% of the debris in
the Great Pacific Garbage Patch comes from land-based activities in North
America and Asia&
the remaining 20% from boaters, offshore oil rigs, and large cargo ships.
The amount of debris in the patch accumulates since most of it is
non-biodegradable, mainly microplastics.
Impact
Destruction of marine life due
to ingestion of toxic and harmful
substances .
These toxic substances also
enters the food chain resulting in biomagnification
Presence of the garbage blocks the sunlight from reaching the planktons
and algae, thereby reducing productivity of marine ecosystem.
It affects the free flow of traffic through oceans.
Impacts the
tourism and
economic livelihood of small Pacific Ocean island countries
2.3 Currents in Indian Ocean
Current
system in Indian Ocean is unique & different from other current systems .
Why it is different than other currents?
In northern hemisphere, it is confined to tropical zone only & that too is divided by
Indian peninsula to form Arabian sea & Bay of Bengal.
Complete reversal in direction of winds as monsoon winds also impacts
the movement of current.
(wind is important factor – direction in which winds flow determine
direction of currents ).
Side Note : Navigation in Indian Ocean.
In Summer , Wind & current flows toward India .
Hence, sea vessel can move from Arabia to India .
In Winter, Wind & current flows toward Arabia .
Hence, sea vessel can move from India to Arabia .
Important for sea trade & cultural interaction since Ancient times.
Significance of Ocean Currents
Ocean Currents play an
important role in earth’s climate by distributing the energy within the
ocean. Along with that, they impact the local climate as
Warm ocean current increases
the temperature of an area
Cold ocean current decreases
the temperature of an area.
Currents also effect the
amount of rainfall.
Warm water currents increase
the rainfall because they bring winds along with them, laden with water
vapours. North America, Ireland,
Britain and south India receive rainfall because of this process.
On the other hand Atacama
desert remains dry because cold water currents don’t play any role in
occurrence of rainfall. Due to
this various deserts are situated on the western coast of Australia,
South America and Africa.
Currents helps in free
navigation navigation as Norweigian Current keeps ports of Scandinavia
navigable throughout the year and Kuroshio Current keeps ports of Japan
navigable during winter.
Conjugation of warm and cold
water currents helps in increasing the development rate of ‘Plankton’,
which is a diet of fish. This
conjugation takes place of eastern coast near New Found land in North
America, Bahia Blanca in South America, Japan coast in Asia etc. But on
the other hand conjugation of
currents forms dense fog which creates problem for marine navigation.
Sometimes ships are not able to move because of this fog. This whole situation effects the
economic activities of respective areas.
3. Vertical Motion of Ocean Water : Upwelling & Downwelling
Vertical circulation of ocean water takes place due to difference in salinity and temperature between the surface and the water deep below.
Upwelling
Upwelling is an oceanographic phenomenon that involves movement of dense, cooler, and usually nutrient-rich water towards the ocean surface, replacing the warmer, usually nutrient-depleted surface water.
UPWELLING & FISHING
Cool & nutrient rich water
come at surface.
Phytoplankton reproduce
rapidly in this condition => Consequently, fishes increase as well.
All Upwelling
Regions in World are good fishing ground. Eg : Canaries,
Benguela and Peru Coast
Downwelling
Down welling is the
process of accumulation and sinking of cold high saline water beneath
warmer or fresher water.
Not good for fishing .
4. Vertical Movement : Tides
What are tides
Rhythmic rise & fall in
level of ocean water.
Causes of tide formations (Prelims-2015) .
Moon’s gravitational pull is the most important
factor.
Sun’s gravitational pull ( although not as
prominent factor as Moon’ pull but still a major factor)
Centrifugal force due to earth’s rotation ( mainly responsible for
causing bulges).
On the
side of Earth facing the moon , a tidal bulge occurs while on the opposite side
although the gravitational attraction of the moon is less as it is farther
away, the centrifugal force causes tidal bulge on the other side
Stages of Tides
Stage I
Sea
level rises over several hours & cover the intertidal zone – flood
tide.
Stage II
Water
rises to highest level – high tide.
Stage III
Sea
level falls over several hours revealing intertidal zone – ebb tide.
Stage IV
Water
level stops falling – low tide.
Syzygy
Alignment of three or more
celestial bodies of same gravitational system in a line.
Effects tides in form of
variation between high tides & low tides.
a. Spring tide
Sun , moon & earth are in
line.
Occur on full moon or new moon (no moon day)
When there is greatest
variation between high tide & low tide .
High tide is higher than
normal high tide & low tide is lower than normal low tide.
b. Neap tide
Sun , Earth & Moon are at
right angle.
Occur when moon is at quarter
phase.
High tide lower than normal
high tide & low tide higher than normal low tides.
Daily frequency of Tides
Earth rotates & moon revolve in same direction, hence in relative term wrt to moon earth take 24 hrs & 52 minutes to complete one rotation.
2 high tides & two low tides in a day (24.52 hours to be exact)=Semidiurnal
Most enclosed water bodies & bodies away from open ocean experience only one high & one low tide .
Tidal Current
Movement of ocean water as a
result of tidal action is known as a tidal current.
In places of narrow coastal
inlet these tidal currents flow rapidly through the mouth with greater
height and velocity. For example in the Bay of Fundy, between Nova Scotia
and New Brunswick of Canada, the difference between high and low tides is
as high as 14m. Ports which utilize the tidal current for entry and exit
of ships from the harbour are known as tidal ports.
Importance of Tides
Creates inter-tidal regions which have special ecology of
their own. Eg : Sunderbans
Since tides are caused by the
earth-moon-sun positions which are known accurately, the tides can be
predicted well in advance. This helps the navigators and fishermen plan
their activities. Tidal flows are of great importance in navigation.
Tidal heights are very important, especially near rivers and
within estuaries having shallow ‘bars’ at the entrance, which helps ships and boats in entering into the
harbour.
Tides are also helpful in desilting the sediments and in removing
polluted water
from river estuaries.
Tides are used to generate electrical power (in Canada, France, Russia,
and China). A 3 MW tidal power
project at Durgaduani in Sunderbans of West Bengal is under way.
5. Thermo-Haline Circulations
Circulation because of the
temperature & salinity of the ocean.
Main driving force is freezing
of water at Atlantic and salinity .
Sequence
First of all water goes to
Polar Region ( Atlantic) . It interacts with the land which is very cold
and freeze . When water freezes, it will increase the salinity of
sub-surface water (because salt separates from water before freezing) .
Subsurface water will become
dense and goes further down. Consequently, it starts to flow as
sub-surface cold current. It will come to South Atlantic ocean and from
there to Indian and Pacific Ocean till the Bering Strait where it upwells
.
Then surface water starts to
flow back .
Note : This process is very slow and time frame between downwelling
and upwelling can take upto thousand years .
Impact of Climate Warming on this
Due to climate change , more
fresh water is being added in Atlantic . This will reduce the salinity
which is the driving force behind whole process.
Hence, climate change and
global warming will negatively impact this circulation
This article deals with ‘Oceanography: Relief features of Ocean.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you canclick here
Introduction
Hydrosphere
covers 70% part of Earth surface and is one of most important Spheres for
various living organisms and vegetation. Of the hydrosphere, 97.2% of water on
Earth is present in Oceans.
The oceans, unlike the continents, merge so naturally into one another that it is hard to demarcate them. The geographers have divided the oceanic part of the earth into five oceans, namely the Pacific, the Atlantic, the Indian, Southern ocean and the Arctic. The various seas, bays, gulfs and other inlets are parts of these four large oceans.
Oceanic Crust
Oceanic Crust is the most
fundamental crust.
It is Basaltic in nature .
Oceanic crust is more denser & darker than Continental Crust.
Age of continental shelfs is 1 billion year, oceanic crust
is younger & nowhere aged more than
200 million years .
Deepest point in ocean is
Mariana Trench (in Pacific ocean near Northern Mariana Islands with depth
10,971 m )
Oceanic Crust
is created at Mid Oceanic Ridge
& destroyed at Trenches.
Ocean floor
is not flat & more diverse than continents & quite different from
continental ones.
Oceans
consist of
71% of earth’s crust.
Division of Ocean
To study ocean bottom properly it should be divided into two divisions
Ocean Continent Margin.
Deep Ocean Plains.
1 . Ocean Continent Margin
Meeting point of ocean & continental crust . It
can be divided into three parts.
Coast / Coastal Plain
Continental Shelf
Continental Slope
Continental Rise
1 . 1 Coast
Coast can
be of two types
Submergent Coast : Estuarine , Ria , Fiord and Dalmatian
Emergent Coast
1 . 1 . 1 Submergent Coast
a. Fiord
Initially mountains are perpendicular to the coast . Glaciers come down to the coast forming u-shaped valley submerging the area. Hence, coastline which was initially straight becomes indented
Eg : Norwegian Coast
b. Ria
If valleys were submerged by rivers (instead of Glaciers) , it is called Ria
Eg : South Hampton, Wales,
British Isles etc
c. Dalmatian
If mountains are parallel to the coast (instead of perpendicular)
If ships are entering this
coast, they face barriers
Eg : Adriatic Coast (Italy)
d. Estuary
If normal low land region (not mountainous) is
submerged at the
mouth of river .
Eg : Thames, Buenos Aires
1 . 1.2 Emergent Coast
a. Lowland Emergence
It usually results in lagoon,
salt marshes, long beaches
Eg : Eastern Coast of India
b. Emergent Upland Coast
No natural harbors are found here
Eg : Scotland
1 . 2 Continental Shelf
Continental shelf is the seaward extension of land that lies under the sea water. It occupies 7% of the sea floor.
It is quite shallow (approx 200m ).
Region is called PHOTIC REGION ie receives large amount of sunlight . Marine organisms are found here (all floating planktons , benthos(crabs) & nektons(fishes)).
It has gentle slope with an average gradient of 1° or even less. The shelf typically ends at a very steep slope, called the shelf break.
Width varies – The shelves are almost absent or very narrow along some of the margins like the coasts of Chile, the west coast of Sumatra, etc. On the contrary, the Siberian shelf in the Arctic Ocean, the largest in the world, stretches to 1,500 km in width . (average width is 80 km)
The depth of the shelves also varies. It may be as shallow as 30 m in some areas while in some areas it is as deep as 600 m (Less depth means it will have more photic zone).
Made up of Granite rock ( because it is part of continental crust).
The continental shelves are covered with variable thicknesses of terrigenous sediments brought down by rivers, glaciers, wind, from the land and distributed by waves and currents. Massive sedimentary deposits received over a long time by the continental shelves, become the source of fossil fuels.
Continental shelves are well known for oil, natural gas, mineral deposits, sulphur, marine fishery etc. Large number of resources are found in continental Shelf.
a. Petroleum
90% of petroleum reserves of
world are found on continental shelves.
Because petroleum is formed
from submergence of marine
living organisms which get converted to petroleum under high temperature
& pressure (marine organisms like fish etc are maximum on Continental
Shelf because of Photic Zone)
Examples : Bombay High, Gulf
of Cambay, Persian Gulf, North Sea, Barents Sea(Russia) , Gulf of Mexico,
Norwegian Sea .
b. Sulphur
Rarely found on land .
Available in sea because
of marine
volcanism .
Gulf of Mexico is rich source of Sulphur.
c. Placer Deposit
Wave action erode beach rocks but there are some materials in rock which don’t disintegrate easily . Disintegrated material of lower weight is moved very swiftly by waves but heavy non-disintegrated material keeps on concentrating on shelf . These are called Placer Deposit.
Example are as follows
Monazite Sand found on Kerala Coast which is source of Thorium . It is important for Indian Nuclear Program
Gold in Alaska .
Zircon on coast of Brazil & Australia.
Diamond on South African Coast .
d. Calcium
Least soluble in ocean water
& can be easily extracted .
Peruvian
coast is rich in Calcium &
Phosphate .
e. Fishes
Due to photic zone and
availability of planktons , fishes are also found in the wasters of
Continental Shelf.
World famous fishing grounds
like Grand Bank are situated here
f. Pearls
Pearls of ornamental value are also found here.
Side Topic : Sea Boundaries (under UNCLOS)
a. Internal waters
All the water that is inside the coastline is called Internal Waters
State has complete sovereignty
over this and it is equivalent to
territory of country
b. Territorial Sea
Upto 12 Nautical Miles (1 NM = 1.85 Km)
(provided there is no other country on the other side. If any other
country is present, it becomes midway)
Here too almost all of the
laws of the land apply. It is almost as good as territory
Vessel of any other nation
need permission to enter into territorial waters of other country &
submarine has to come on surface & declare its identity while
navigation .
c. Contiguous Zone
Upto 24 Nautical Miles .
Some dilution of political
laws
Navy & Coast Guard cant
guard this but if criminals like smugglers after doing some crime try to run then that
country can follow them till this point .
d. Exclusive Economic Zone (EEZ)
Upto 200 Nautical Miles.
All the economic
laws of country apply but political
laws don’t apply here
Country can explore both biotic and abiotic
resources of the water and ocean floor .
Other countries have right to
peaceful passage .
Exceptional Case
If Continental shelf is beyond 200 Nautical Miles , country can claim EEZ upto that point with maximum limit of 350 NM
Within this extended zone, state has exclusive right of exploiting and exploring non-living resources of the sea bed as well as sedentry species on the sea bed. Fishing rights arent inclusive in 200 to 350 Nautical Miles.
d. International waters / High Sea
Beyond EEZ
Here resources belong to
everyone. No nation has sovereign rights over this area.
Side Topic : Nautical Mile
It is the distance
per one
minute of latitude (1/60th of 1 degree)
1 Nautical Mile = 1.85 Km
(1.85*60=111 Km = Distance
covered per degree latitude . )
At equator, 1 degree of longitude is also 111 km . But this distance
keep on reducing while going North and South and is 0 at poles . But distance
between latitudes is always same (because they are parallel) and is 111 km
approx at every point
1 . 3 Continental Slope
The zone of steep slope extending from the continental shelf to the deep sea plain or abyssal plain is called continental slope.
It has very steep slope .The slope angle varies from 5° to 60°.
No deposition is possible because of steep slope . Hence, no resources are found in this zone.
But some unique landforms are created specially when there is mouth of very large river at continental shelf like Indus, Ganga, Mississippi, Yukon & Congo. Example of such landform are
SUBMARINE CANYONS in which flow of water would be so great that it will vertically erode both continental shelf & slope . In Indian Ocean, submarine canyons are found at mouths of river Ganga and Indus.
Underwater Waterfalls – Highest waterfall on earth is under the Denmark strait.
1 . 4 Continental Rise
Transition between Continental
Slope & Sea Floor.
There would
be no continental rise in case there is TRENCH after Continental
slope .
2 . Deep Ocean Plains
Major portion of Ocean Crust consist of Deep Ocean Plains which have various relief features like Mid Ocean Ridge, Islands, Guyots etc. These are as follows :-
2 . 1 Abyssal/ Deep Sea Plains
Occupies 40% of ocean floor.
Consists older parts of oceanic crust that are smoothened
due to sediment deposition.
Among flattest, smoothest
& least explored regions of earth.
Average depth varies from 3000
to 6000 metres .
It has deposits from
continents( terrigenous), marine life(biogenous) & salts and
minerals(inorganic).
Abyssal plains of Southern
Indian Ocean and Eastern Pacific Ocean are rich sources of Poly Metallic
Nodules.
Side Topic : Poly-Metallic Nodules (PMN)
Polymetallic Nodules (AKA Manganese Nodules) .
Multiple metals are concentrated around core .
Found at depth of around 4,000 to 6,000 m on the floor
Were first found around Kara Sea & Arctic sea but later nodules were found in all oceans .
But are economically viable to extract only in Central Indian Ocean & Eastern Pacific Ocean.
Composition : Manganese (Highest) and apart from this contain Iron , Silicon, Al, Nickel & Cobalt & some rare metals.
Important for India as India doesn’t have good source of Nickel & Cobalt .
Countries are in race to explore & extract PMN.
2. 2 Islands
An island is a landmass surrounded by water on all sides.
They are of four types
a. Continental Island
Once part of large continent.
Examples : Sri Lanka,
Madagascar, Vancouver, Baffin islands.
Note : Madagascar Island formed after separation from Indo-
Australian Plate
Generally bigger in size than
all other categories of Islands.
Rock composition and all of
continental island is same as plate from which it is separated .
b. Volcanic Island
Ocean – Ocean plate collision
or Hotspot activity.
Marine organisms, the coral
polyps colonize the tropical warm water and form islands known as coral
islands.
Examples include Lakshadweep,
Maldives, Mauritius, Bahama & Bermuda
d. Sandbar Island
Formed by accumulation of sand
near coast => Sand which is eroded from main land is again settled near
coast & if continental shelf is shallow nearby then sandbar island is
formed .
Example : Long Island (New
York)
Side Topic : Archipelago
Cluster of islands .
(GK) Largest archipelago.
By area
Indonesia
By number of islands
Finland
2.3 Coral Reefs
Corals are indicative of health of Marine Ecosystem ie if coral reef exists at any place in healthy way , entire ecosystem is healthy.
Wherever there is coral reef , you will find great biodiversity at that point.
Most diverse ecosystem of world => 10% area but 25% marine species . They can be said to be Rain Forests of the Ocean.
What are corals?
Corals are tiny fleshy Sea Anemones Polyps.
They extract Calcium from sea
water for their skeletons to protect their body.When one generation die
other generation comes on it.
Corals live in symbiotic relationship with microscopic algae- Zoo-xanthalae which have photosynthesis
capabilities.
Zoo-xanthalae provide food to
corals and corals provide protection to zooxanthalae.
Conditions conducive for corals
Water temperature in
the range of
22-29 degrees
Celsius. Thus,
areal distribution of
corals is limited to tropical
and sub-tropical zones.
They will
not flourish in
areas of cold
currents but thrive
in warm current
regions. Therefore, they
are generally absent
on western coasts
of continents.
Depth
of water should
not exceed 180 feet
as the sunlight
is too faint
for photosynthesis which
is essential for survival
of microscopic Zoo-xanthalae
on which coral
polyps depend. However,
there should be plenty of
water as polyps cannot survive for too long
out of water.
Water should be
salty and
free of sediments.
Corals are best
developed on seaward
side of reef,
where constantly moving waves, tides and currents maintain an abundant supply
of clear, oxygenated water
Spatial Distribution of corals in the world
Spatial distribution of Corals in India
In India
they are found in
Gulf of Mannar.
Andaman &Nicobar
Lakshadweep
Gulf of Kutch
Sindudurg coast ( near Malvan
Coast) in Maharashtra ( only here
in India, bleaching hasn’t happened yet)
While
the Lakshadweep reefs are atolls, the others are all fringing reefs.
Coral Bleaching
When corals are in stress they expel Zoo-xanthalae.
Zoo-xanthalae give the colourful appearance to corals . In their absence, corals seems white (their original colour) .
Ultimately without food corals will die out too.
Reasons of coral Bleaching
Global Warming : increase in sea surface temperature .
Ozone Depletion : increase in solar irradiation.
Ocean Acidification : because of increase in Carbon Dioxide in atmosphere . This Carbon Dioxide dissolves in ocean water & water becomes acidic . Corals can’t live in acidic water
Algal Bloom : excessive use of fertilisers go to ocean through rivers resulting in Algal Bloom . Sunlight cant go below & corals die.
Increase in sedimentation from rivers.
Marine pollution like oil spills . No sunlight & oxygen reach below.
Diseases.
Coastal construction and shoreline development: Results in heavy sedimentation
Coral mining: Live coral is removed from reefs for use as bricks etc.
Consequences of Coral Bleaching
It will impact marine
ecosystem, as coral reefs are some of the most bio diverse and productive ecosystems.
Reefs act as natural barriers to shorelines, protecting them from the
effects of moving water. As coral reefs die, coastlines become more susceptible to damage and
flooding from storms, hurricanes, and cyclones.
Ocean will not be able to absorb as much
Carbon Dioxide
because Zoo-xanthalae
absorb Carbon Dioxide for photosynthesis leading to increased Global Warming.
Measures need to be taken
Political measures: The global agreements combating climate change must
keep the needs of coral islands as top priority.
Switching to sustainable livelihood measures: It is high time to recognize
the carrying capacity of each coral island ecosystem and limit population
growth, tourist foot fall etc. at these islands.
Sustainable development : Avoid major projects in threatened areas. Eg :
Carmichael Coal Mine in Australia that threatens Great Barrier
Reef should be avoided.
Formation of Coral Reef
Coral Reef
can be developed both at margins of continents or around islands .
3 stages of coral formation are as follows
Stage 1 : Fringing
Coral reef starts to develop along margin
of an island
& subduction of island just starts
First stage of Fringing Reef
Stage 2 : Barrier Reef
Corals keep on accumulating
and keep on rising upwards. As a
result, large part of island is submerged in sea/ocean.
Lagoon formation occurs
Stage 3 : Atoll
Last Stage
Island is submerged & only ring remains visible .
Note : In India, while the Lakshadweep reefs are atolls, the others are all fringing reefs.
Side Topic : Great Barrier Reef , Australia
Adani’s are investing in Coal Fields in Australia (Carmichael Coal Fields) . Project will create jobs for
Australians and coal will be imported to India
But due to large
Carbon-dioxide emissions in the area
, Great Barrier Reef will be impacted heavily.
2.4 Oceanic Trench/ Oceanic Deep
The long, narrow, steep-sided
depressions formed along the
convergent boundary where one plate subducts below the other is called Ocean trenches.
The Challenger
Deep in the Mariana Trench, (10,994 m) in the Pacific Ocean
is the deepest part of the earth.
Most trenches are in Pacific ocean & they are most active geological feature. Great earthquakes
leading to Tsunamis occur here.
As many as 57 deeps have been
explored so far; of which 32 are in the Pacific Ocean; 19 in the Atlantic
Ocean and 6 in the Indian Ocean.
Main Trenches of the world
2.5 Seamounts / Guyots
Flat topped volcanic hills submerged under the sea water are called guyots.
Seamounts are conical, volcanic hills submerged
under ocean water
Seamounts , guyots and the water column above them serve as
important habitats, feeding grounds and sites of reproduction for many
open-ocean and deep-sea species.
2.6 Abyssal Fans
Also known as Deep Sea Fans or Underwater Deltas or Submarine Fans .
Delta like structure formed at deep sea surfaces . Major reservoirs of biodiversity.
2.7 Mid Oceanic Ridge
Mid-ocean ridges are submarine mountains.
Mid oceanic ridges are located on the divergent plate boundaries where magma flows through the fissure to form new oceanic crust. They form the longest mountain range in the world extending for more than 56,000 km long.
This article deals with the‘Issue of Poverty.’ This is part of our series on ‘Governance’ and ‘Economics’ series, which is an important pillar of the GS-2 and GS-3 syllabus respectively. For more articles, you canclick here.
Introduction
What is Poverty?
Poverty is a social concept which results due to unequal distribution of benefits of socio-economic progress.
How does it manifest itself?
Poverty manifests itself in the following ways
Hunger & Malnutrition
Lack of access to education and health care
Social Discrimination
Lack of participation in decision making
World Bank definition
World Bank
defines extreme and moderate poverty in the following way
Extreme poverty
Living on less than $ 1.25 per day.
Moderate poverty
Living on less than $ 2 per day.
Note – Poverty is measured in Purchasing Power Parity(PPP) exchange rate & not absolute exchange rate.
A recent World Bank Report has shown that extreme poverty in India more than halved between 2011 and 2019 – from 22.5 per cent to 10.2 percent.
Poverty Gap
It measures the Depth of poverty
It is also called Foster-Greer-Thorbecke (FGT) Index.
Engel’s Law
Engel Law states that when incomes rises, percentage of overall
income spent on food items decreases. This is known as ENGEL’S LAW.
SDG & Poverty
Sustainable Development Goals gives utmost importance to poverty. The First SDG talks about ending poverty in all its forms everywhere by 2030.
India is home to 26% of the global extreme poor. Hence, the Indian role in achieving that goal is most important.
Causes of Poverty
Economic Reason
Growth Model not conducive to poverty alleviation: India chose a capital-intensive model in a labour-intensive country, which was a great fault.
Widespread reliance on agriculture (42% population is dependent on sector contributing 17% to the GDP)
Lack of formal institutional credit pushes a large number of Indians into poverty every year.
MATTHEW EFFECT: The phenomenon, widely spread across advanced welfare states that the middle class tends to be the primary beneficiary of social benefits & services targeted to the poor (India is trying to rectify this using Targeted Delivery of Subsidy with the help of Jan Dhan-Aadhar-Mobile).
Demographic Factors
Rapid Population growth in India is also the primary cause of poverty as enough resources were not available for all.
Social Cause
Caste system: The subordination of low caste people by the high caste people caused poverty of the former.
Joint family system: Joint Family System, followed by many families in India, provides social security to its members. As a result, some people take undue advantage of it and live upon the income of others. They become idlers. Their routine of life consists in eating, sleeping and begetting children.
Social Customs: Ruralites spend a large percentage of annual earnings on social ceremonies like marriage, death feasts etc., which force them to take debt and remain trapped in poverty.
Climatic Factors
Drought, Floods, Cyclones etc. perpetuate poverty.
Historical Factors
Historical reasons such as colonialism & imperialism led to the exploitation of Indian people. India’s wealth was drained to metropole Britain for two centuries.
Institutional Factors
Withdrawal of Government from Social Security, especially after LPG Reforms.
Anti-poverty schemes are not successfully implemented due to institutional inadequacies.
Poverty Line
What is Poverty Line?
The poverty line is the threshold income and households earning below this threshold are considered poor.
Different countries define the poverty line in different ways depending on local socio-economic needs.
Different approaches to define the poverty line
There are two approaches regarding this
Nutritional Approach: It is based on specific minimum criteria of nutrition intake
Relative Deprivation Approach: It doesn’t take into account just nutritional deficits, but in comparison to the progressive section, the person is not that progressed. E.g., a person earning less than 60% of the country’s per capita income
Developing countries generally follow the nutritional Approach. But
now the time has come that India should move from the Nutritional Approach to
the Relative Deprivation Approach to ensure sustainable and equitable
development.
Poverty line in India is decided by
Earlier it was used to be determined by erstwhile Planning Commission
Now NITI Aayog determines the Poverty Line. NITI Aayog made the Commission under Arvind Panagariya recommend Poverty Line in India.
Panagariya has suggested that
Tendulkar Committee’s report should be accepted for poverty line estimation.
But socio-economic indicators, say, as collected by Socio-Economic Caste Census, should be used to determine entitlement for benefits.
Various Committees constituted for Poverty Line Determination
1. Lakdawala Committee
In books, we frequently come across the Poverty Line defined as 2400 calories in Rural & 2100 calories in Urban. This definition of the Poverty Line was based on the recommendations of the Lakdawala Committee (1999).
2. Tendulkar Committee
Tendulkar Committee
defined Poverty Line based on per capita monthly expenditure.
While calculating, Tendulkar Committee based its recommendation on food, health, education and clothing.
According to Tendulkar Committee Report, Poverty has declined in
India from 37.2% in 2004 to 22% in 2011.
3. C Rangarajan Committee
C Rangarajan Committee defined Poverty Line based on Monthly Expenditure of family of five.
Rangarajan Committee took more things than Tendulkar Committee into its calculations
Rangarajan Committee
also recommended delinking the
Poverty line from the Government entitlement benefits. Food Security benefits
should be given as per Social and Caste dimensions and not BPL.
4. Saxena Committee on Rural Poverty (2009)
When Tendulkar Committee Report came, the Ministry of Rural development hurriedly set up a committee known as the SAXENA COMMITTEE in 2009 to review the methodology for inclusion of a person in the BPL Category to include them in government schemes.
Recommendation of the Committee
Committee gave the famous Automatic Inclusion and Automatic
Exclusion principle.
The automatic inclusion criterion for the most vulnerable sections of society (E.g. homeless people, persons with disabilities etc.)
Automatic Exclusion: Those having motorbikes etc.
Apart from being Automatically included, find other using scores of various deprivations.
5. Hashim Committee on Urban Poverty (2012)
To suggest a methodology for inclusion of a person in the BPL category in Urban Areas to include them in government schemes.
Recommendations of the Committee
Automatic Exclusion
Automatic Inclusion
Scoring Index: remaining households will be assigned scores from 0 to 12 based on various indicators. They should be considered eligible for inclusion in the BPL List in the increasing order of higher scores.
Multidimensional Poverty Index
In India, we calculate poverty using Tendulkar Method based on household consumption.
But UNDP takes a holistic view of poverty and measure it differently.
The report has been released since 2010.
In Multidimensional Poverty, they look into the following components to measure poverty (HES)
Health with components like child mortality
Education with components like years of schooling
Standard of Living with components like Electricity, water etc.
Andhra Pradesh is already using this approach.
Capability Approach to Poverty by Amartya Sen
Traditional Approach
Poverty is defined by an individual’s income.
E.g., Extreme Poverty is defined as those who live on $1.25 per day or less.
As a result, following this approach, governments centre their Poverty Removal Policies on job creation, GDP growth and other economic policies.
Capability Approach
In richer countries, all are fortunate enough that they can earn a good income. Does that mean they are not poor?
Amartya Sen’s Capability approach defines poverty in a Holistic Way. A better approach to look at poverty is the deprivation of a person’s capabilities to live the life they value.
Well Being Approach
Given by Erik Allard, it
includes three dimensions as:
Having (Material),
Loving (Social), and
Being (Spiritual-emotional)
World Poverty Clock
The World Poverty Clock was developed by World Data Lab to monitor global progress toward ending extreme poverty.
The latest data (released in March 2024) shows that India has managed to reduce extreme poverty to below 3% of its population.
Critique of these Poverty Lines
Experts argue that the Indian way of calculating poverty is incorrect. It is simply what some call a “starvation line”. Critics argue that governments around the world keep the poverty line at low levels to show that millions have been moved out of poverty.
India should be using some relative measure as opposed to the absolute measure to define poverty. In most Europe, a family with a net income of less than 60% of the “median net disposable income” is counted as poor. A poverty line “relative” to the national average also gives an idea about the state of inequality.
A comparison shows that India’s poverty line is abysmally low than even African Poverty Lines. Even the poverty line of Rwanda is higher than that of India. The per capita poverty line of a rural adult Rwandan in Indian terms comes out to be Rs. 900/ month, more than Rs. 816 for a person in rural India.
Another critique that Poverty Line faces is that once decided, the PL remains the same for years & don’t take into account inflation. It needs to be updated every year by applying a cost inflation index to keep it realistic.
Multidimensional Poverty Index: We define poverty in a minimal way by just looking at household consumption. UNDP defines poverty using the Multidimensional Poverty Index, which takes a holistic view and considers indicators like Health, Education, and Standard of Living. India should move toward that.
Reduction of Poverty in India
According to Tendulkar Committee Report,
poverty in India has reduced from 37.2% in 2004 to 22% in 2011.
Reduction in poverty is attributed to
Increase in employment in the non-agriculture sector – The construction sector absorbed the landless labourers & daily wage earners from villages
Schemes like MGNREGA, National rural livelihood mission also reduced the stress during the lean season by creating employment opportunities during the non-agricultural season.
India’s demographic bulge provided more working population compared to dependents (Children and elders).
Social welfare schemes like PDS, AAY, MGNREGA, NRLM, Pension schemes and others provided a safety net to the poor
Inward remittances – Large emigration of the citizen to the US, EU etc. and to west Asian destinations like UAE, Saudi, Qatar etc. generated huge inward remittances for India, which directly benefited dependents in India
Quality jobs in the Service sector like BPO, Hospitality, Retail chain, E-commerce supply chain provided heavy wages.
The rapid growth of the economy provided better opportunities to come out of poverty through better employment opportunities, increased demand for services etc.
Chinese Case Study
According to World Bank, people living below the poverty line reduced from 770 million in 1978 to 5.5 million in 2019.
In 2021, China declared that it had eradicated extreme poverty.
Steps taken by Government in this regard
Targeted Approach: China identified the poorest region to allocate more resources there.
Economic Development: China’s economic development generated a lot of jobs, helping people to come out of poverty
Social Welfare Programs: The government provided healthcare coverage, education, housing assistance etc.
Agriculture and Rural Development: China focused on agricultural reforms, modernization, and supporting farmers.
Impact of LPG Reforms on Poverty
Poverty has decreased: Consider any Poverty Line, all points to the fact that Poverty in India has declined. Take the example of the extreme poverty line as defined by the World Bank.
Inequality: Inequality in India has increased after LPG Reforms.
The
rich section has reaped the benefits of LPG Reforms. This is the leading cause
of the increase in Inequality.
The above Paradox can be explained by the Redistribution of Income by Government. Because of the increase in income of richer sections, the government is getting more taxes. Therefore, redistribution of this source has ensured that Poverty has decreased.
Impact of Poverty
Several issues like hunger, illness and thirst are both causes and effects of poverty. Hence, the term known as poverty trap is usually used for this i.e. bad cycle is created not allowing people to come out of poverty
On Society
Poverty results in inequalities which can culminate into violent upheavals like Arab Spring. Various Revolutions in Arab Spring started because of the lack of jobs and high poverty levels.
On Children
Poverty leads children to build antisocial behaviour and social exclusion.
Terrorism
Most of the time terrorists do come from poor countries with high unemployment.
Diseases
Diseases are very common in people living in poverty because they lack the resources to maintain a healthy living environment.
Education
Those living below the poverty line cannot attend schools and create a vicious cycle in which poverty prevents people from getting a good education, and being uneducated prevents them from escaping poverty.
How can India reduce poverty?
Even though India has grown rapidly, its growth has been less effective at reducing poverty than in some of India’s middle-income peers such as China, Vietnam, Brazil and Turkey. The following can be done in this respect.
In Agricultural sector
With 4
out of every 5 of India’s poor living in rural areas, progress will need to
focus on the rural poor. Hence, the government should focus on following to
increase the income of those involved in the agriculture sector.
Value addition through food processing
Organic farming
Cooperation farming, milk cooperatives, and farmer producer organizations.
In Manufacturing Sector
Create Jobs in India via
Skill development
Make in India
Startup India
In Service Sector
Creation of quality jobs in BPO, IT and ITES for youth
Promotion of tourism
Promotion of higher job creation in e-commerce, supply chain, Hospitality and construction sectors.
In Governance
Implement Jan Dhan- Aadhar- Mobile (JAM) effectively to target subsidy to the poor and eliminate inclusion and exclusion errors.
Look into the feasibility of providing Universal Basic Income.