This article deals with ‘Wind Systems’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you canclick here
Winds
Wind is the horizontal
movement of air molecules from areas of high pressure to areas of low
pressure to maintain the atmospheric equilibrium.
Nomenclature of Winds
Winds are named easterly,
westerly, northerly etc on basis of direction
of their origin.
Easterly wind is that which
originate in east & blow from east to west.
Wind direction is identified
by an instrument called Wind Vane and wind speed is measured by
Anemometer.
Factors affecting direction & velocity of wind
1 . Pressure Gradient
If pressure gradient is more, velocity will be
more in magnitude
because differences in atmospheric pressure produces a force.
The wind always moves
perpendicular to isobars.
2. Frictional Force
Lower is frictional force,
greater will be the speed .
Over the sea surface the
friction is minimal.
3. Coriolis Force
If the earth did not rotate,
the winds would blow in a straight path. Then the rotation of the earth
results in Coriolis effect and it deflects the direction of the wind.
Northern Hemisphere
Deflect towards Right or Clockwise (NCR)
Southern
Hemisphere
Towards
Left or Anticlockwise.
Coriolis force is directly proportional to the angle of latitude. It is maximum at
the poles and is absent at the equator.
Type of Winds
1 . Primary / Global/ Permanent Winds
Pressure belts lead
to the formation of primary wind system resulting in Trade Winds,
Westerlies and Polar Easterlies
1.1 Trade Winds
The winds blow from the sub tropical high pressure belt towards the
equatorial low pressure belt.
Due to Coriolis Effect, these winds are deflected to the right in the northern
hemisphere and to
the left in the southern hemisphere.
As winds are named after the
direction from which they originate they are called as the North East and South east trade winds.
As the winds favoured trading
ships they are called as ‘Trade winds’.
Side Topic : Tropic Deserts & Trade Winds (aka Trade Wind Deserts or Trade Deserts)
Tropical easterlies/ Trade Winds flow from east to west . Hence, windx becomes dry when they
reaches the western coast of continent as all the moisture is already shed in form of rainfall on
eastern coast .As a result, in tropical region, deserts are found on
western coasts of continents .They are also known as Trade Deserts.
Apart from that, Cold Currents
near the western coasts of continents also provides desiccating imapct on
the surrounding lands leading to more dryness .
1.2 Westerlies
Westerlies flow towards the
Sub Polar High from Sub-Tropic Low
They turn towards right and
left in northern and southern hemisphere respectively due to Coriolis
force.
As they flow from West to
East, they are called Westerlies
Ocean is dominant in the
southern hemisphere between the latitudes 40º and 60ºS. Hence the
westerlies are so powerful and persistent that the sailors used such
expressions as “Roaring Forties”,
“Furious Fifties” and “Screeching Sixties” for these high velocity winds in the latitudes
of 40º, 50º and 60º respectively.
1.3 Polar Easterlies
Polar Easterlies flow towards the Sub Polar High from
Polar High .
They turn towards right and
left in northern and southern hemisphere respectively due to Coriolis
force.
As they flow from East to
West, they are called Easterlies
2 . Secondary / Regional / Seasonal Winds
Monsoon and Cyclones are considered to be Secondary or Seasonal Wind
2.1 Monsoons
Monsoons are seasonal winds
which reverse their direction due to various reasons .
These winds bring rainfall in
India and are the major climatic feature of climate of Indian
Sub-continent.
We will detail with these
winds in Indian Climate .
2.2 Cyclones
Wind blowing in circular manner around an area of low pressure
Due to Coriolis effect – blow
in anticlockwise direction in
Northern hemisphere
& clockwise direction in southern hemisphere.
Cyclones are of two types.
Tropical
cyclones
Develop
over oceans in summers in tropical regions . Eg : in Bay of Bengal, China sea , Caribbean sea etc.
Temperate
/
Extra
tropical
Develop
in middle latitudes in winter season
More
about cyclones in separate article
3. Tertiary / Local Winds
Tertiary winds are formed due to pressure gradients which may develop on a local scale because of differences in the heating and cooling of the earth’s surface.
3.1 Sea and Land Breezes
Sea Breeze : During daytime, land heats up much faster than water. The air over the
land warms and expands leading to formation of low pressure. At the same
time, the air over the ocean remains cool because of water’s slower rate
of heating and results in formation of high pressure. Air begins to blow from high pressure over
ocean to the low pressure over the land. This is called as ‘Sea breeze’.
Land Breeze : During night time, the wind blows from land to sea and
it is called as ‘Land breeze’
Note
: Sea breeze and land breeze influence
the movement of boats near the coastal region and fisher men use these winds
for their daily fish catching. Fishermen go for fishing at early morning along
the land breeze and return to the shore in the evening with the sea breeze.
3.2 Mountain and Valley Breezes
Valley Breeze / Anabatic
Winds : During the day, mountain
hillslopes are heated intensely by the Sun, causing the air to expand and
rise. This draws in air from the valley below, creating a valley breeze.
Mountain Breeze / Katabatic
Winds : During the night the hillslopes get
cooled and the dense air descends into the valley as the mountain wind
3.3 Warm and Cold Local Winds
Cold Local Winds
High Pressure conditions are created in areas situated
in high latitudes due to cold weather. As a result, air starts to come down and diverge into
different directions (forming anti-cyclones) blowing as ‘Cold and Dry
Local Winds’ and reducing temperature of surrounding regions as well.
In Siberia
such anti cyclonic winds are created and diverge in different
directions . These winds are called
Buran
Buran
Explained above
Mistral
(Europe)
Cold northerly
from central France and the Alps to
Mediterranean
Bora (Eastern
Europe)
North easterly
wind from eastern Europe to north eastern Italy
Blizzard
(USA & Canada)
Cold and dry snowy
winds blowing in USA and Canada
Pampero
(Argentina)
Cold and dry
wind blowing in Pampas of Argentina
Southern
Bursters
Cold and dry
wind blowing in Australia
Warm Local Winds
Low pressure develops over Deserts and low latitudes in
summers due to excessive heating of land . The air starts to move upward
and diverges in different directions blowing as upper tropospheric wind. They carry sand
and dust with them and raises temperature of regions over which they flow.
These winds are known with different names in different regions like
Loo
India (Punjab,
Haryana, Rajasthan, UP, Delhi etc)
Sirocco
From
Sahara desert to Italy and Spain after crossing
Mediterranean Sea
Khamsin
Egypt
Harmattan
From Sahara desert
to Gulf of Guinea
Other type of warm and local winds like Chinook winds develop when warm, moist air blows from the adjoining ocean (
Pacific Ocean in this case) towards the Mountain range situated near the
coast (Rockies in this case). In such situation, dry and warm air over the
mountain will descend in the adjoining valley on the leeward side of wind
. Other such type of winds are Fohn
and Zonda
Chinook
US and
Canada
Rockies
Fohn
Europe
Alps
Zonda
Argentina &
Uruguay
Andes
Santa Ana
California
Santa Ana
Mountains
Upper Atmospheric / Meridional Circulations
Hadley cycle
Air from
equator being lighter move up & diverges toward poles & descends at
subtropical areas causing higher pressure there. That wind is again carried
by trade winds to equator.
Ferrel Cycle
Same thing between subtropical & subpolar
pressure belts
Polar cell
Between polar & subpolar pressure belts
Side Topic : Upper Tropospheric Winds and Geostrophic Winds
To understand
formation of Jetstreams, it is important to know what are Geostrophic winds.
Unlike air moving close to the
surface, an air parcel in the upper troposphere moves without a friction
force because it is so far from the source of friction—the surface. So,
there are only two forces on the air parcel, the pressure gradient force
and the Coriolis force.
A useful heuristic (i.e.
theoretical model) is to imagine that air parcel in the upper troposphere
is starting from rest under the influence of ‘Pressure Gradient Force
” moving from point of High
Pressure to Low Pressure .
Due to pressure
gradient force and absence of friction force , speed of wind will keep on increasing . Since, Coriolis
force increases with increase in speed and acts perpendicular to Pressure
Gradient Force, situation will be
reached when Pressure Gradient Force equals Coriolis Force & these winds will deflect 90° (clockwise) . At this point, the
flow is no longer from high to low
pressure, but parallel to the isobars. Such winds are called Geostrophic
winds
These are also known as Upper
Tropospheric Westerlies
Jetstreams
are an example of Geostrophic winds .
Direction of Geo Strophic winds
Always
move from WEST TO EAST (hence called Westerlies)
Northern
Hemisphere
– Geostrophic winds deflect clockwise . – Move from West to East.
Southern
Hemisphere
– Geostrophic winds deflect Anti Clockwise. – Move from West to East.
Jetstreams
Jet
streams are special type of Geostrophic winds .
These are strong and narrow bands of meandering wind
blowing at height of 6 to 14 km ( just below Tropopause) at very high
speed of upto 450 Km/hr. They occur at points where atmospheric pressure
gradients are strong and friction force acting on moving air is absent.
Jetstreams flow in
wavy fashion and create alternate High Pressure & Low Pressure zones .
Location of Jet Streams
They aren’t found
arbitrarily . They are situated
at typical positions like where two
Meridional Circulations meet. (Reason : Point where two air masses of different temperatures
meet, the resulting pressure difference is highest. Only in such condition, Pressure
Gradient Force can increase the speed of wind to such an extend that
Coriolis Force can balance the Pressure Gradient Force and rotate it by
90°) (I know it is hard to understand. To properly understand what is
happening, you can refer this useful video What is the jet
stream and how does it affect the weather?)
Hence , 4 permanent Jet
streams are always found .
2 Polar Jet
Between
Polar cell & Ferrel cell.
2 Sub
Tropical Westerly Jet (STWJ)
Between
Ferrel cell & Hadley cell.
Apart from that, there are some temporary Jet-streams like
Tropical Easterly Jetstream
Somali Jetstream
Speed of Jetstreams
Cause of Jetstreams is the pressure difference (due to temperature
difference) in the upper atmosphere. Hence , higher the pressure gradient (or temperature
gradient) higher will be speed of Jetstream.
Temperature variations are
more in winters (lowest ~ -70 C & highest ~ 15 C) compared to summers
(lowest ~ 20 C & highest ~ 55 C) . Hence, Jetstreams are faster in
winters of the respective hemisphere.
Importance of Jetstreams
1 . Sub Tropical Westerly Jet Stream (STWJ) & Indian Weather
It is centred around 25° N & S at altitude of 12 km & is strong in winter season with velocity of 40
mph.
It greatly determines
the weather of Indian Sub continent .
During summer until it is
present over Indian subcontinent , High Pressure is maintained over there
& monsoon can’t start. Only when STWJ moves above Himalayas &
low pressure is created over Indian subcontinent , monsoon hits India.
Western Disturbances : STWJ comes to India
after passing over Mediterranean Sea where rainfall occurs during winter. STWJ bring those cyclonic disturbances to north India along
with it. This results in winter rain & hailstorms in North India & occasional high snowfall in hilly
areas .
2. Jetstreams and Frontal / Temperate Cyclones
Jetstreams play important role in formation of Temperate Cyclones which are important feature of the climate of temperate regions like Britain etc .
3. Tropical Easterly Jet and Somali Jetstream
These Jetstreams play
important role in the Indian Monsoon.
More about this can be read in
(chapter) Indian Climate .
4. Role in Aviation Industry
If aeroplanes moves in the direction of Jetstream, it can lead to large fuel savings and vice-versa
Impact of Climate Change on Jetstreams
Due to Climate change and Global warming, Earth’s Polar regions are warming more rapidly than other parts . This has resulted in weakening of Polar Jet Streams because temperature contrast that drives Jetstreams has decreased.
This article deals with ‘Pressure and Pressure Belts’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you canclick here
Atmospheric Pressure
Atmospheric pressure is
defined as the force per unit
area exerted against a surface by the weight of the air molecules above
the earth surface.
Atmospheric pressure is
measured by an instrument called ‘Barometer’
The atmospheric pressure is
not distributed uniformly over the earth. The amount of pressure increases or
decreases, according to the amount of molecules, that exerts the force on
the surface.
When temperature of air
increases, the air expands and reduces the number of molecules over unit
area leading to reduction in pressure.
Similarly, when the
temperature falls, the air contracts and the pressure increase.
Factors affecting Atmospheric Pressure of area
1 . Temperature
As the temperature increases,
air expands because of which its density decreases resulting in low
pressure over area.
On the other hand, cold
climate makes air denser resulting in high pressure over area.
Equatorial regions have low
pressure because of high temperatures. On the other hand Polar regions
have high pressure due to low temperature.
2. Height from Sea
The pressure at sea level is
highest and keeps on decreasing rapidly with increasing altitude because
of the progressive reduction of the mass above the point where it is
measured.
3. Humidity
Water vapours are light in weight therefore pressure of humid air is less compared to dry air.
4. Gravitation of Earth
Atmosphere glues around the
Earth due to its gravitation
Due to shape of earth, Polar regions are nearer to core of the
Earth as compared to Equatorial regions and hence have higher air
pressure.
5. Rotation of Earth
Rotation of Earth results in
centrifugal force. Centrifugal
force pushes things away from its core.
Centrifugal force is highest
over equator and zero over poles. Hence,
air pressure will decrease in Equatorial regions as compared to
that in polar regions.
Distribution of Atmospheric Pressure
Horizontal distribution of pressure is studied by drawing isobars . Isobars are lines connecting places having equal pressure. In order to eliminate the effect of altitude on pressure, it is measured at sea level. These distributions change with season as well.
Pressure Belts of Earth
Atmospheric pressure
belts envelope on the surface of the earth. They are equatorial low pressure
belt, sub tropical high pressure belts, sub polar low pressure belts and polar
high pressure belts
1 . Equatorial Low Pressure Belt
Region extending between 5° N
latitude to 5° S
Following are the reasons
creation of low pressure belt over this region :
Rays of sun fall vertically
=> High temperature creates low pressure.
Owing to high temperature,
evaporation process is also very fast => large amount of water vapours
decrease the weight and density of air resulting in reduction of air
pressure.
Rotation of Earth and
resulting centrifugal force has its maximum magnitude on Equator
When air moves upward , it
leads to formation of clouds .
Hence, it rains heavily in these
areas (Cumulonimbus
clouds & Convectional rainfall) . There is single
season throughout the year ie high temperature & high rainfall
.
Advection is absent in this
region because gradient of pressure is low
. Hence known as Belt of
Calm / Doldrum .
2. Sub-Tropical High Pressure Belt
At about 30°N and 30°S
latitudes on both sides of equator
Air which rises in equatorial
region begins to cool when it reaches higher altitude over equatorial
region and flows towards the poles. This wind collides with the wind
coming from the polar region at higher altitude and subsides down over sub
tropical latitudes. This leads to formation of high pressure belt
It is said that to avoid the
slowing down of ship due to high pressure, the horses were thrown into the
sea. So this belt is called as ‘Horse latitude’.
3. Sub Polar Low Pressure Belt
These are low pressure belts
found at 60°N and 60°S latitudes on both sides of equator
The warm westerly wind from
sub tropical region moves towards the pole and collide with the cold polar
easterly wind from polar high pressure region and raises up to form sub
polar low pressure belt.
4. Polar High Pressure Belt
Region at poles on both sides
of equator
In this region, high pressure
is formed because temperature remains low for whole of the year.
Side Note : Basis of formation of pressure belts
Pressure belts can be created because of two reasons
1 . Temperature / Thermally formed
The Equatorial Low Pressure Belt and Polar High Pressure Belt are formed due to high and low temperature respectively. Hence, these are ‘thermally formed pressure belts’
2. Dynamically formed
The Sub Tropical High and Sub Polar Low pressure belts are formed due to movement and collision of wind systems. Hence, they are called ‘Dynamically formed pressure belts’.
This article deals with ‘Temperature and Heat Budget of Earth’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you canclick here
Air Temperature
Air temperature of a
particular place denotes the degree of hotness or coldness of air at a
given place. It is generally measured in Celsius
Heating process of Atmosphere
There are different ways of heating & cooling of the atmosphere.
Conduction :The air in contact with the land gets heated by
conduction . Conduction is important in heating the lower layers of the
atmosphere.
Convection : The air in contact with the earth rises vertically on heating in the form of
currents and further transmits the heat of the atmosphere. This process of
vertical heating of the atmosphere is known as convection. The convective
transfer of energy is confined only to the troposphere.
Advection : The transfer of heat through horizontal movement of air is called advection. (In northern India, during summer season local winds called
‘loo’ is the outcome of advection process).
Radiation (Green House effect) : The insolation received by the earth is in
short wave form and it heats up surface.
The earth after being heated itself becomes a radiating body and it
radiates energy to the atmosphere in long wave form. The
long wave radiation is absorbed by the atmospheric gases particularly by
carbon dioxide & other Green House Gases. Thus, the atmosphere is
indirectly heated by the earth’s radiation.
Heat Budget of Earth
The earth as a whole
does not accumulate or loose heat. It maintains its temperature. This can
happen only if the amount of heat received in the form of insolation equals the
amount lost by the earth through terrestrial radiation. This is known as Heat Budget
of Earth
This is done in following way
Suppose 100 units are coming to earth
Factors affecting Horizontal temperature distribution
1 . Latitude of the place
Insolation received
by any place depend upon latitude because when we move from equator
towards pole, sun-rays become slanted . In slanted
sun-rays, same energy is diffused over large area
Conclusion :
Temperature
decreases from the equator to the poles.
2. Distribution of Land and Water
Compared to land, the sea gets heated slowly and loses heat slowly. Land heats up and cools down quickly.
So more land mass in northern hemisphere leads to higher average temperature than the southern hemisphere
3. Presence of warm & cold current
Places located on the coast where the warm ocean currents flow record higher temperature than the places located on the coast where the cold currents flow.
4. Air mass circulation
The passage of air masses also affects the temperature. The places, which come under the influence of warm air-masses experience higher temperature and the places that come under the influence of cold airmasses experience low temperature.
5. Cloudiness
Cloudy sky obstructs the solar radiation from
the sun to reach earth. Hence, clear sky increases the temperature of
place.
Due to this, Maximum insolation is received over
the subtropical deserts, where the cloudiness is the least. Equator receives
comparatively less insolation than the tropics because of clouds.
6. Nature of Surface
Albedo ie ability of surface
to reflect the sunrays also impact temperature of place.
Fresh snow has albedo of upto
90% and more reflection from the
snow surface leads to low temperature accumulation compared to bare land.
7. Local aspects
Depend on position to position.
Factors affecting vertical temperature distribution
The temperature decreases with increasing altitude from the surface of the
earth.
Reason : Atmosphere is
indirectly heated by terrestrial radiation
from below. Therefore, the places near the sea-level record higher
temperature than the places situated at higher elevations.
The vertical decrease in
temperature of troposphere is called as ‘Normal Lapse Rate’ which is 6.5 C
per 1000 meter of ascent.
Temperature Inversion
Normally , within
Troposphere, temperature decreases with increase in height . But if reverse happens, it is called Temperature Inversion .
Since cold air is
denser/heavier than warm air , in case of temperature inversion, air will not be
able to move upward .
When Temperature Inversion can happen
At Tropopause : Temperature starts to increase from here
. As a result, air packets reach till Tropopause & then starts moving
downward . There is no vertical air
movement after that
A cool winter
night with no clouds and stable air : Air above cold surface gets cold but layer above cold air is still warmer &
hence it cant move upward . This phenomenon is prominent till 400 m above
earth’s surface.
Valley
Inversion/Air Drainage :
In winter, mountain top becomes cold quickly compared to valley . As a result, cold air comes down to occupy valley . This uplifts warm air of valley &
situation is created when lower layer is cold & upper layer is
warm
Frontal inversion occurs when a cold air mass undercuts a warm air mass and lifts it
Implications of Temperature Inversion
1 . Formation of Fog
As we have seen in
currents , where ever warm &
cold current meet , fog is created
In same way , when
warm air & cold air meets , fog is created . This lowers the visibility in
region.
2. Atmospheric Stability
Temperature Inversion prevents
upward & downward movement of air.
Hence, it discourages
rainfall.
3. Impact on Agriculture
Frost formed due to valley inversion damages
crops in foothills,
whereas trees and vegetation at top of hills and mountains are not
damaged. The valley floors in the
hills of Brazil are avoided for coffee cultivation because of frequent frosts.
(Beneficial Case :
Though generally fog (caused due to temperature inversion) is unfavourable
for many agricultural crops such as grams, peas, mustard plants, wheat
etc. but sometimes they are also favourable for some crops such as coffee plants in Yemen hills of
Arabia where fog
protect coffee plants from direct strong sun’s rays. )
4. Environmental problem
In winters,
concentration of pollutants raises to very high levels in cities as due to
temperature inversion, air gets trapped . Eg : Delhi’s pollution levels are more
in winters than summers.
Urban Heat Island
An urban heat island
is an urban area or metropolitan area that is significantly warmer than its
surrounding rural area due to high concentration of high rise concrete buildings, metal
roads, sparse vegetation cover and less exposure of soil. These factors
cause urban regions to become warmer than their rural surroundings, forming an
“island” of higher temperatures.
This article deals with Composition and Structure of Atmosphere’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you canclick here
Introduction
Atmosphere is combination of
two words ‘Atmo’ and ‘sphere’. It means that region of Earth which has ‘air’.
Atmosphere is present as life
saving layer between outer space and land surface. It is the source of
important gases which are important for the existence and continuity of
life. It also filters the harmful rays travelling towards Earth
Composition of Atmosphere
Earth’s atmosphere is composed of a mixture of various gases .
It is held to earth by gravitational forces
Atmosphere is denser at sea level & thins or gets rarefied rapidly upward . It should be noted that, 99% of the mass of atmosphere is confined to height of 32 km
Percentage of different gases (by volume) in atmosphere is as follows :-
Atmospheric gases don’t
interact with each other chemically & don’t lose their own property.
These gases can be divided
into two groups based on their distribution horizontally
Permanent
Gases
– Nitrogen , Oxygen, Hydrogen & Argon. – Their quantity remain same on all places .
Variable
Gases
– Water Vapour , Carbon dioxide & Ozone – Their quantity vary from region to region. Eg : In coastal areas, there will be more water vapours and in cities, there will be more Carbon dioxide. – They can absorb heat & hence known as Green House Gases.
Based on vertical distribution, they can also be
grouped into two groups. Heavy gases like Nitrogen , Oxygen and Methane have high composition near
earths surface. While going up, composition of lighter gases keep on
increasing but since there is high turbulence, no effective separation
occurs in most of gases except for
two gases.
Water Vapour
Near
surface of earth, they are upto 2% by volume but no trace present above
10-12km.
Ozone
Found
mainly between 10-50 km in stratosphere.
Side Note : Important gases in Atmosphere ( not on basis of percentage but function )
1 . Nitrogen
Present in atmosphere in
highest proportion (78%)
It is very important for
living organisms because it is an important element of Amino acids which
form protein
2 . Oxygen
Second most abundant gas in
atmosphere (21%)
All the living organisms use
it for breathing
3. CO2
Meteorologically very
important gas .
It
is transparent to incoming solar radiation but opaque to outgoing
terrestrial radiation . Hence, it is mainly responsible
for Green House effect.
4. O3
Ozone gas is found between
10-50 km
It act as filter and absorb UV rays .
But scientists are very
concerned about the depletion of ozone layer due to action of chlorofloro
carbons on Ozone
5. Water Vapour
Variable gas
Can be upto 4% by volume in wet tropics
In dry & cold areas of desert & polar deserts it can be less than 1% of air .
It also absorbs parts of the insolation from the sun and preserves the earth’s radiated heat.
6. Dust
May originate from different
sources & include sea salts, fine soil, smoke-soot, ash, pollen, dust
& disintegrated particles of meteors.
It is concentrated
in lower parts , yet convectional air currents can take them to great heights .
They perform two very
important functions
It provides Hygroscopic nuclei
around which water vapour condenses to produce clouds .
They absorb and reflect small amount of radiation
rays of sun.
Structure of Atmosphere
Atmosphere can be divided into five distinct layers based on the thermal characteristics and temperature variations (note : these divisions are based on thermal characteristics)
1 . Troposphere
Troposphere is the lowest layer of atmosphere and it is
very important for all the living organisms
Name has been derived from
Greek word ‘Tropos’ which means mixing
and ‘sphere’ which means ‘region’. Hence, ‘troposphere’ means
‘region of mixing’
Troposphere is zone of air
turbulence because in this zone,
convectional air currents rise due to heating of earth surface
Thermal Characteristic of Troposphere
Temperature decreases with increase in height
(reaches – 60 degree Celsius at
tropopause).
In normal conditions, the rate of decrease of temperature is
(ie lapse rate) is 6.5 degree Celsius per kilometre . This happens
because of decrease in gases with increase in height
However, due to local
reasons, at some places this phenomena reverses also (called Temperature
Inversion).
Height of Troposphere
on Equator, it is 18 km
(gases are heated up and rises upward from strong convectional currents)
on poles, it is 8 km (gases
are cold and settles down)
At average its height is upto
12 kilometre from ground.
All weather phenomena occur in
this layer as it has dust particles and water vapour. This layer has
clouds which produce precipitation on the earth.
Tropopause
It is the region between
Troposphere and Stratosphere which is 1.5 kilometre high
The fall in temperature comes
to an end in this region
Turbulent mixing of gases,
winds, and radiation etc. none of the weather activities take place in
this region
2. Stratosphere
Stratosphere extends from end of Tropopause up to a height of 50
km from the earth’s surface.
The lower part of this layer is
highly concentrated with ozone gas which is called as
‘ozonosphere’. It prevents the harmful ultra-violet rays from the Sun to
enter into the lower part of the atmosphere
Thermal Characteristics of
Stratosphere
Temperature increases with
height (ie from – 60 degree Celsius at start to 0 degree Celsius at
Stratopause) .
Temperature increases because
of absorption of ultra violent rays by ozone gas
It is turbulence free zone . Hence, it
is ideal for flying jet aircraft.(important prelims question)
3. Mesosphere
Mesosphere lies above the
stratosphere, which extends up to a height of 80 km from earth’s surface .
Thermal characteristics of
Mesosphere
In this layer, once again, temperature starts decreasing with the increase
in altitude
From 0 degree Celsius at
start, it reaches up to minus 100°C at the height of 80 km.
Most of the shooting stars get burned in
Mesosphere .Luminous noctilucent clouds form here due to the presence of
cosmic dust. ( important prelims question)
It is the coldest layer of
earth .
4. Ionosphere /Thermosphere
It extends from 80 km to 400
km above Earths Surface ..
It is called
ionosphere due to presence of electrically charged ions that reflect radio waves back and thermosphere
because it is at very high temperature.
Thermal characteristics of
Ionosphere
Temperature
increases rapidly with height .
The temperature
increases rapidly up to 1,000 degree Celsius. This is due to absorption
of high energy solar radiation and cosmic waves ( which break molecules
to ions).
How
Ionosphere is formed ?
High energy
sun rays and cosmic rays break
atoms of gases in this region .
Molecules
become ionised (positive charged ).
These are highly energised
particles & behave as free particle .
Luminous phenomenon
called auroras at higher latitudes
when Solar Winds are able to reach ionosphere and collide with ions
present in this layer (Aurora Borealis
(Arctic Zone ) & Aurora Australis(Antarctic Zone) )
Use
of Ionosphere in radio communication : It is useful in radio
communication because ions can
reflect radio waves.
5. Exosphere
Outermost layer of
atmosphere and lies from 400 km to
1000 km from earth’s surface.
This is the highest layer but
very little is known about it.
It has rarefied contents. It
contains mainly oxygen and hydrogen atoms. These atoms can travel hundreds
of kilometres without colliding with one another. Hence, matter in
exosphere doesn’t behave like gases.
It gradually merges with outer
space.
Magnetosphere/ Van Allen Radiation Belt
Magnetosphere lies above
Atmosphere and extends from 1000 km to 36000 km from earth’s surface
Although it isn’t part of atmosphere but plays important
part in shielding earth
from solar & other cosmic winds .
Magnetosphere is formed due to earth’s magnetic field and it prevents
most of solar
winds(highly
energised particles) from reaching earth .
Polar cusps: regions above geomagnetic poles where solar wind can enter relatively easy to earth’s atmosphere.
Magnetospheric
Storms
Magnetospheric storms are temporary disturbances in earths magnetic field caused by occurrence of magnetic flares & sunspot. In this process, material from solar coronal mass ejection hits earth
Major effect in such event is global disruption of radio & telegraphic communication.
Aurora
Luminous phenomenon observed in high latitude
regions .
May appear as rolling lights
or coloured streaks .
Produced
by entry of charged
particles from sun into earth‘s
atmosphere & collision of these charged particles
with ionised particles in ionosphere . They emit energy on interaction leading
to formation of aurora.
Entry of
these charged particles occur at Cusp . Hence, formed at particular places
on earth (& not everywhere)
Occur in Ionosphere.
Most frequent during intense period / solar minimum of sun spot cycle(sun spots have
cycle of 11yr).
Side Topic : Sunspot , Sunspot Cycle & Solar Minimum
Sun-spots are the regions on the sun
where the solar
magnetic field is very strong (and as a result, it doesn’t allow solar
streams to escape the sun)
Sun-spot cycle is the solar
magnetic activity cycle with the average time period of eleven years.
Solar minimum is the period
of least solar activity in the eleven year solar cycle. During this time, sunspot activity
diminishes. According to NASA and other agencies, a solar minimum is about to occur in 2020-21.
Impact of Solar Minimum
During the solar minimum, coronal holes can last for a longer time. Coronal holes are vast
regions in the sun’s atmosphere where the sun’s magnetic field opens up
and allows streams of solar particles to escape the sun.
It could enhance
events of geomagnetic storms & auroras, potentially
disrupting communications and navigation systems.
Sun’s magnetic field weakens
and provides less shielding from the cosmic rays. This can pose an
increased threat to astronauts travelling through space.
This article deals with ‘External Benchmark System .’ This is part of our series on ‘Economics’ which is important pillar of GS-3 syllabus . For more articles , you can click here
Issue
When RBI
decreases Repo Rate, Banks don’t decrease their interest rates proportionately.
Why banks don’t transmit Repo Rate cuts to borrowers?
a. Banks don’t depend on RBI
In India(& all developing countries ) ,RBI is not the main source of money to banks . Common people are main supplier(mainly because people don’t have much option to invest money in alternate investment facilities eg mutual funds etc )
b. Small saving schemes rate not reduced
Transmission is limited by high small savings rates. Banks worry that if they cut their deposit rates, customers will flee to small savings instruments.
c. High Statutory Liquidity Ratio
Large money has to be kept idle as SLR which
banks cant lend
This reduces their ability to
pass the benefit to consumers .
d. Banks increasing their Spread
Due to losses incurred to
banks as a result of high NPAs
& lowering of Credit Demand , Banks are increasing
their Spread in order to maintain
their profits in absolute term.
This has reduced the capacity
of banks to decrease Lending Rates.
To deal with inadequate transfer of Repo Rate cuts by banks to borrowers , RBI Came up with MCLR and External Benchmark Rate System
How Banks decide their Interest Rate
Timeline
1969
Government
began nationalization of private banks, and ‘administered interest rates’ on
them.
1991
M.Narsimhan
suggested deregulation: Government should not dictate / administer
individual banks’ interest rates & RBI should only give methodology to
banks.
2003
RBI
introduced Benchmark Prime Lending Rate
(BPLR).
2010
RBI
introduced BASE Rate + Spread system; update
frequency was on individual
banks’ discretion.
2016-17
RBI introduced Marginal Cost of Funds based Lending Rate (MCLR) +Spread system.
2019
RBI introduced External Benchmark Rate System.
Marginal Cost of Funds based Lending Rate (MCLR)
Banks to calculate lending rate on monthly basis.
Lending Rate to be calculated using CRR Cost, Operating Cost, Marginal cost of funds (calculated using Repo Rate) (don’t need to go into detail. Just remember, MCLR has Repo Rate as component)
Lending Rate = MCLR + Spread (to be decided by banks)
Benefits?
Better transmission of
Monetary Policy
Transparency &
accountability to borrowers.
RBI’s Janak Raj internal study group(2017) showed MCLR did not yield all benefits . Banks keep on increasing ‘Spread’ based on their discretion .
So new method was introduced
External Benchmark System
Applicable from April 2019 (on recommendations of Dr.
Janak Raj Committee)
NEW loans to be linked with
External Benchmark system.
In this system
Bank will be asked to choose any benchmark like
Repo rate or
91-day T-bill yield or
182-day T-bill yield or
any other benchmarks by Financial Benchmarks India Pvt. Ltd.
It has to be updated atleast
every 3 months.
Lending Rate of Bank will be External Benchmark +
Spread (eg if
Bank choose Repo Rate as External Benchmark, then Interest Rate will be
Repo Rate + Spread)
This article deals with ‘Reformist Movements– UPSC.’ This is part of our series on ‘Modern History’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Introduction
Main reason why Britain emerged as powerful nation was it
accepted modern civilization first among all nations . But in India , intentionally they followed the policy
to stall the change
in society . Changes did occur & Indian society did try to change but
not due to British policies but due to efforts by some progressive Indians
These efforts happened first in Bengal because it came under British control
first . First lot of Indians who studied in Western English knowledge were
also created in Bengal at the end
of 18th Century. New intellectual stirrings created reformed mentality . They didn’t reject Indian tradition but sought to change certain
unreasonable aspects of Hindu society which didn’t conform to their
rationalist ideas.
Later , British officials also joined the race & this provided legitimacy to the reform
agenda of the Utilitarian reformers like Bentinck .
But problem was , this
mentality was confined to a
small circle of English Educated elite. Series
of reforms followed but they remained on paper . They faced problem
because they never attempted to develop modern social consciousness from
below . They should have followed ‘bottom up approach’ instead of
‘top down approach’
. Reform forced from above remained
ineffective .
Untouchability as an issue of social reform had to wait
until the beginning of the twentieth century and the arrival of Mahatma
Gandhi in Indian public life after World War One .
Lacking in a broad social
base, the reformers of the early nineteenth century thus exhibited an
intrinsic faith in the benevolent nature of colonial rule and relied more
on legislation for imposing reform from above. There was very little or no attempt to create a
reformist social
consciousness at the grass-roots level, where religious
revivalism later found a fertile
ground.
The reform movement broadly fell under two categories
Reformist Movement
– Eg : Brahmo Samaj, Prarthana Samaj & Aligarh Movement – Relied on reason & conscience. They wanted to purge outdated elements from the religion which didn’t pass on the scale of reason .
Revivalist Movement
– Eg : Arya Samaj, Ramakrishna Mission & Deoband Movement – Relied upon traditions & wanted to go back to their self made golden past
Side Topic : Why Britishers tried to reform Indian Society in 19th Century?
There were various reasons for this
Several ideological influences in Britain, such as Evangelicalism, Utilitarianism and free trade
thinking.
For renewal of Charter of company
Pro socio-religious reform
thrust in contemporary England => because Progressive Whig Party came into power back in
Britain.
Role of Christian missionaries was also noticeable.
But the Company’s government was still tentative about interfering
for fear of adverse Indian reaction unless a section of the Indian society was
prepared to support reform. Such a group was soon to emerge through the
introduction of English education
Status of Woman &Civilizational Critique
Status of woman
became the main focus of the reforming activities of colonial state as
well as educated Indians
At that time, way in which civilisations were ranked , position of
woman was one of the important criteria & here Indians
were increasingly under attack by western observers from missionaries to
civilians . Indian civilisation was
despised because it assigned such a low status to women .
Hence, Indian Intelligentsia
responded to this civilisation critique by advocating & supporting reforms to
improve status of woman in Indian society.
But such reforms remained very
restricted to only few women belonging to high class because women remained recipient of male patronage & never became involved in
these reformist projects as conscious
subjects of their own history .
Upper Class Women vs Peasant Women
Peasant woman
were better compared to Upper caste woman during that time
They didn’t practice Purdah
System , Right to Remarry was there
& Sati was also not that widespread among Peasant class unlike
Higher caste
Reformist Movements
We have seen the reasons why Social Reform movements were started in India. Now we will look in detail into one strand of these movements known as Reformist Movements .
Features of reformist social movements
a. Confined only to narrow social group
Reformist spirit appealed only
to a small elite group who were primarily the economic & cultural
beneficiaries of the colonial rule
.
In Bengal
– Small number of western educated elite known as Bhadralok – Socially they were mostly Hindus & although caste wasn’t a major criteria for membership, they were mostly higher caste Brahmin, Kayastha & Baidya
Western
India
– Members of Prarthna Samaj were mainly English educated Chitpavan & Saraswat Brahmins along with Merchants from Gujarat
Indeed the high caste character of the early 19th century
explains to a large extent the relative
silence on caste question & untouchability which had to wait till Gandhi
b. Faith in benevolent nature of colonial rule
They had great faith in the
benevolent nature of colonial rule & infact existence of these classes
depended on Colonial rule .
Because of faith , they relied more on legislation for imposing
reform from the above
c. Colonial Character of the reforms
Dominant colonial
assumption was religion
was the basis for Indian society &
this religion was encoded in the scriptures . Social evils
were thought to be result of the distortion
of scriptures by self seeking people , in this case the cunning Brahmins who
had the monopoly over this textual knowledge .
Civilising
mission of the colonial state thus seen to lie in giving back the natives
the truth of their own little read & even less understood shastras .
Whole debate over
Sati was grounded in scriptures & its abolition was not based on fact
that it is morally & ethically
wrong but when government was convinced that custom was not enjoyed by the
scriptures .
As the colonial rulers gave supreme importance to scriptures, the Indian reformers too, as
well as their detractors, referred to ancient religious texts to argue
their respective cases. The brutality or the irrationality of the
custom, or the plight of women, whom the reform was intended for, were
lesser concerns in a debate
Note : The intellectuals did not however attacked the social system as a whole; their attack centred only on the perversions and distortions that had crept into it. They did not advocate a sharp rupture in the existing social structure of the country. They did not stand for structural transformation; changes were sought within the framework of the very structure. They were advocates of reform and not revolution.
Social problems and Reformist efforts to reform them
a. Female Infanticide
It was most common in Western & Northern India .
There landowning high caste families , practising hypergamy found it difficult to find suitable grooms for their daughters or pay high demands of dowry . Hence, they killed their female offsprings at birth .
British authorities tried to persuade them & after 1830 sought to coerce them to desist from practice but no tangible effect was observed.
In 1870, Female Infanticide Act was passed . But even after that, condition didn’t change because abject neglect of female children resulted in high mortality .
b. Sati Abolition
Sati Abolition was the
greatest achievement of Lord Bentinck .
Sati is self immolation of
wife on funeral pyre of dead husband.
According to social
reformers , it has always been there much the exception rather than a rule
in Hindu life & during Mughal period, it was practiced in Rajputs & Kingdom of Vijayanagara . But during British period, it revived on much larger scale
& experienced highest rate of development.
Reasons for practice of Sati
Earlier it was practiced by Upper Caste
Hindus but during
British rule, it started in peasant
families of lower & intermediate
caste who achieved social mobility & then sought to legitimize their new status by imitating their caste superiors.
Greed of the relatives – Child marriage was widespread at that
time & many a times bride who has not even lived with groom was forced
to perform Sati in order to get property of that man.
Sati was widespread in areas where Dayabhaga school of personal Hindu law was applicable . Areas where ] Mitakshara
school was
applicable, it was less prevalent because Mitakshara
school gives lesser rights to wife to inherit property
Campaign against it
First started by Christian Missionaries
But very strong campaign under
Raja Rammohan Roy gave real momentum
Finally in 1829 , Governor
General Bentinck prohibited
Sati by Govt Regulation Act XVII. Pressure was also put by the Court of Directors because they wanted to present credible image of Company’s rule in India in the
British Parliament
before renewal of Charter
pending in 1833.
Although it reduced very much after that but
the idea & myth of Sati persisted in popular
culture & was continually reaffirmed through epics, ballads & folktales
. Case
of surfaced even in 1987 ( Roop Kanwar Case of village Deorala in Rajasthan).
c. Widow Remarriage
Main protagonist was Ishwarchandra Vidyasagar . But he too, like Raja
Rammohan Roy looked to colonial state for piece of legislation for
this .
In 1856 , Hindu Remarriage Act was passed but
this couldn’t make the
practice socially acceptable . Along with that, Act was intrinsically
conservative in nature because on remarriage , widow
disinherited her deceased husband’s property .
Movement ended with its
unavoidable death . Vidyasagar failed to see widows remarried because this
needed social consent which could
not be generated by piece of legislation .
Practise of Widow Remarriage
remained rare & exceptional among the educated class &
within few years taboo universalised & penetrated to lower castes.
Western India
1860s : Movement to
promote widow remarriage spread among educated class & debate became sharp between reformers &
detractors.
1866 : Vishnushastri Pandit started a Society for
Encouragement of Widow Remarriage while opponents started rival
organisation .
Movement ended in whimper . By end of century only 38 such marriages happened & in that cases
too couples were subjected to enormous social pressure & ostracism .
Madras Presidency
In Telegu speaking
areas , movement was started by Veersalingum Pantulu . In 1878 , Society for
Social Reforms was founded by him for this.
1881 : first widow remarriage
officiated by him in 1881 in face of stiff opposition but till 1891 ,
support increased & he formed Widow Remarriage Association with
patronage of prominent citizens .
North India : Haryana
Here practice of widow remarriage was already
there& new act provided
such marriage with legitimacy & further social acceptance
d. Child Marriage
Vidyasagar continued his campaign against Polygamy & later
Child Marriage .
In 1860 , finally he was able
to secure an Age Of Consent
Act, 1860 that fixed age of
consent for consummation of marriage at 10 years which was raised to 12
years in 1891.
But census showed that it
continued to be practiced widely among all castes.
e. Thugee
Variousperipatetic groups
were stereotyped into the colonial construct called Thugs who were believed to have
been members of a fraternity traditionally involved in robbery & ritual killings in the name of religion
Campaign against thugee was
initiated in 1830s by Lord Bentinck
Thugee Act (XXX) , 1836 was passed & Thugee
Dept. was created
for prosecuting gangs seen as perpetrating a crime in the name of religion
but it’s elimination proved to be a difficult task.
In 1839 , Sir William Sleeman as head of Department claimed that
thugee had been exterminated but in reality he begun to realise difficulty
in doing this and it was just a face-saving measure.
f. Slavery
Laws were even more
ineffective against less organised social customs that remained part of
everyday life from centuries .
Slavery was such an example .
Slavery was abolished in Britain in 1820 & in India too Charter of 1833 instructed government to abolish slavery & Parliamentary pressure
continued till it was abolished .
But
problem was, they tried to see slavery
in India through lens of their British idea of Slavery but in India where
agrarian relations were complex & marked by numerous structures of
labour dependencies it was almost impossible to stop it
Process was failure in India
Bengal Renaissance
Renaissance literally means ‘rebirth’. It refers to the revival of Graeco-Roman (classical) learning in 15th-16th century after long winter of dark ages. In Indian context , intellectual revolution that took place in the nineteenth century in the fields of philosophy, literature, science, politics and social reforms is often known as Indian Renaissance. An important part of this Renaissance was reforming Hinduism from within on the basis of Post Enlightenment Rationalism.
Very much like the Italian Renaissance, it was not a mass movement; but instead restricted to the upper classes.
Response of the educated Indian elite to civilisational critique was to reform Hinduism from within, in the boundary of post enlightenment rationalism . Such phenomenon is known as Bengal Renaissance
Movement was started in Bengal by Raja Rammohan Roy who is often described as Father of Modern India .
Raja Rammohan Roy(1772-1833)
Personal life
He was Hindu Brahmin and was born in Hooghly ,Bengal
He fought against the stagnant
society .
He was one of those upper caste
gentry whose power & position had been enhanced by Permanent
Settlement &
other opportunities opened by the Colonial rule.
He studied Persian and Arabic at a Madrasah in Patna . He was proficient in Arabic,
Persian, Sanskrit & European languages like English, French, Latin ,
Greek & Hebrew
At a time when Bengali youth
under the influence of western learning was drifting towards Christianity,
Roy proved to be the champion of Hinduism . Although, he defended Hinduism against the hostile criticism of the
missionaries , he sought to purge Hinduism of the abuses that had crept
into it.
Then he studied Vedantic monism & after his migration to Calcutta in 1815, he was exposed to the Christian
Unitarianism . Such intellectual influences motivated him to contest the
missionary claim of superiority of Christians . His answer to this was to reform Hinduism using reason by going back to its purest form
as enshrined in Vedanta
texts
Raja Rammohan Roy accepted the
concept of ‘One God’ as propounded by Upanishads . For him God was shapeless , invisible & omnipresent but the
guiding shape of the universe . He declared his opposition to idol worship
& was of view that worship to be performed through prayers &
meditation & readings from Upanishads . He translated Upanishads into Bangla to demonstrate
that ancient Hindu scriptures themselves propagated monotheism
He published his first philosophical work, Tuhfat-ul-Muwahhiddin
in 1805 in which
he analysed the major religions of the
world wrt ‘reason’ and ‘social comfort’. He denied that religion was merely a matter of
faith outside reason and attempted to expose the myth of miracles associated with it.
Later, he started English Hindu college at Calcutta in 1816
He was great exponent of the
Bengali language .
He also
started Persian
newspaper MIRAT UL AKHBAR ( mirror of news) and Bengali newspaper Samvad Kaumudi.
He was given the title of Raja by
Mughal Emperor Akbar II , who sent him to England
in 1831 as Ambassador of the king to ensure that Bentinck’s Regulation of
banning the practice of Sati is not overturned and also to overturn
the decision to make Mughals
Princes & taking royal titles from them
He died there at Stapleton
,Bristol in 1833 (due to Meningitis)
Social ideas
Worked for the emancipation
of the women
Sati System was abolished on
account of his efforts . Government passed Anti Sati legislation in 1829
declaring sati as a criminal offence
He condemned polygamy, early marriage and opposed
the subjugation of women and their inferior status in society. He related their problems to
the root cause of absence of property
rights. To him, female
education was another effective method to free Indian Society from social
stagnation
To propagate his message
against Sati he started a Bengali newspaper SAMVAD KAUMUDI (moon of
intelligence )
Worked against the rigidity of
the Caste System
Education
He favoured
maximum age of Civil services to be 22 years
Favoured Jury system
Founded Hindu College(1817) along with David Hare , Radhakant Deb,
Maharaja Tejchandra Ray of Burdwan , Prasan Kumar Tagore , Babu Budhinath
Mukherjee & Justice Sir Edward Hyde ( Hindu College later became Presidency College( in
1855) & Presidency
University (in 2010)
He
supported Macaulay in favouring English language
In 1825 , he started Vedanta College which offered both
Indian & western knowledge
He also compiled Bengali
Grammar
Political views
He raised not only social issues but political and economic issues too
He stood for
Indianisation of services
Trial by jury
Separation of Powers between the executive and the judiciary
Freedom of the Press
Judicial equality between Indians and Europeans
Criticised the Zamindari System for its oppressive practices
He was progenitor of nationalist consciousness, and ideology in India. His every effort of social and religious reform was aimed at nation-building.
In particular, he attacked the rigidities of the caste system which, according to him, had been the source of disunity among Indians. He held that the monstrous caste system created inequality and division among the people on the one hand, and ‘deprived them of patriotic feeling‘ on the other.
Rammohan was an internationalist, libertarian and democrat in his orientation. He took active interest in international affairs and wanted amity among nations. His concern for the cause of liberty, democracy and nationalism led him to cancel all his social engagements when he came to know of the failure of the Revolution in Naples in 1821. By giving a public dinner, he celebrated the success of the Revolution in Spanish America in 1823.
Newspaper and Books
Roy started following newspapers and pamphlets
Sambad
Kaumudi – Bengali Newspaper
Mirat ul
Akhbar – Persian Newspaper
Pamphlet
– An Exposition of Revenue &
Judicial System in India (urged government that administration & judiciary
should be separated among other things )
Along with that , he wrote following books
Gift to Monotheists (1809)
Percepts of Jesus (1820)
Tuhfat-ul-Muwahhiddin in 1805
Mahanirvana Tantra (1797)
Religious ideas
Propagated MONOTHEISM and Vedantic Monism.
He opposed the idol worship
Organisations
a. Atmiya Sabha – Calcutta
Started in 1815
It was a philosophical discussion circle
Discussed monotheism in Hindu Vedantism
It was also attended by Dwarkanath Tagore (Grandfather of Rabindranath)
Opposed worship of idols
Against rigidity of caste & meaning less religious rituals
He blamed the Brahman priests for perpetuating religious evils by keeping people ignorant about the true teachings of the scriptures.
b. Brahmo Samaj
Started as
Brahmo Sabha in 1828 (later became Brahmo Samaj)
Founded by Dwarkanath & Raja Rammohan Roy
Main Theme – rid Hinduism of its evils & preach
monotheism
Purpose was to purify Hinduism of all evils which
had crept into it
Opposed idolatry
It vehemently opposed Sati System.
Brahmo Samaj
Started at
Calcutta
Year
1828
By
Raja Ram
Mohan Roy & Dwarkanath Tahore
Works done by Brahmo Samaj
It propagated Monotheism (discarded the faith in divine Avataras) .
It was against idolatry and idol worship
It attacked Casteism & Untouchability
Any scripture could enjoy the status of ultimate authority transcending reason & conscience .
It took no definite stand on the Doctrine of Karma & Transmigration of soul & left it to the individual Brahmos to believe either way.
Worked for respectable position of the women in the society and for this
Condemned Sati
Favoured abolition of Purdah System
Discouraged Child Marriages & Polygamy
Crusaded for widow remarriage etc
After Roy’s death in 1833, the leadership of the Brahmo movement was taken over by Debendranath Tagore who provided the movement with a better organisational structure and ideological consistency
But the movement was actually taken out of the limited elite circles of Calcutta literati into the district towns of east Bengal by Bijoy Krishna Goswami and Keshub Chandra Sen in the 1860s.
Goswami bridged the gap between Brahmoism and the popular religious tradition of Vaishnavism
Sen’s specific focus was to reach larger numbers of non-Westernised Bengalis in the eastern Gangetic plains and to take the movement outside Bengal to other provinces of India
Schisms & other Developments
First schism in the Samaj in 1866
Brahmo
Samaj for India
– Led by more radical Keshav Chandra Sen, Anandamohan Bose & Shiv Narayan Shastri . – Reverted away from the Hindu components and accepted the teachings of all religions
Adi
Brahmo samaj
– Under Debendranath Tagore (Father of Rabindranath) – Remained in a more inclusive and Hindu sphere of influence
Basically, as Meredith Borthwick has shown, it was a schism between Keshav’s followers, for whom social progress and reform were more important than anything else, and the followers of Debendranath, who preferred to maintain their identification with Hindu society.This rift was, as it became clear soon, more about an identity crisis than about any fundamental difference of ideology: while some of the Brahmos wanted to define themselves as separate from the Hindus, others began to seek a position within the great tradition of Hinduism.
Second Schism in 1878
A band of Keshub Chandra Sen followers left him
On account of
Marriage of Sen’s minor daughter to Prince of Cooch Bihar
Also because he became devout follower of Ramakrishna and tried to bridge Brahmanism and Brahmo Samaj.
They Started Sadharan Brahmo Samaj and worked mainly for the social work & female education and famine relief . Consisted of Anand Mohan Bose & SN Shastri
Thus Brahmo samaj also contributed prominent nationalists who later formed the backbone of the moderate phase of congress
In 1881, Sen formed his Naba Bidhan (New Dispensation) and started moving towards a new universalist religion. But by this time , successive ideological rifts and organisational divisions had weakened the Brahmo movement, confining it to a small elite group.
Limitations
Limited to urban areas only
Lot of internal rivalries
Achievements of Brahmo Samaj
Abolition of
Sati : Pressure
was put by the samajis & as a
result Anti Sati legislation was passed
by Lord William Bentinck in 1829
Worked for
Abolition of the caste system and dowry system
Emancipation of the women
Improving educational system
Brahmo Samaj ultimately failed and emerged as sectarian religious order after continuous schisms but nevertheless , its achievements were huge
Rabindranath Tagore admitted the failure of Samaj but also recognised the very important role played by Samaj of providing a shock to static Indian society and made it to think on rationalist lines.
According to Bipin Chandra Pal , main impact of Samaj was on Political Culture . It was from Brahma Samaj that idea of free thinking individual emerged who would be able to absorb democratic & western ideals.
Henry Vivian Derozio & Young Bengal Movement
Derozio
(Anglo-Indian Teacher at Hindu
College) started Young Bengal Movement
At age of 17, he started Young
Bengal Movement.
He was much more modern than Raja Ram Mohan Roy.
He was a free thinker and a rationalist, helped promoting a radical & critical outlook among
his students who questioned authority, loved liberty and worshipped truth.
Most radical at that time
& was inspired by French Revolution
First
nationalist poet of Modern India
Derozians,
the followers of Derozio, were staunch rationalists; they measured everything
on the yardstick of reason. He organised debates where ideas and social
norms were freely debated. In 1828, he motivated them to form a literary
and debating club
called theAcademic Association.
In 1838, they formed ‘Society for the Acquisition of General Knowledge‘, where they discussed
various aspects of Western science, and stood for a number of social
reforms, such as the prohibition of caste taboos, child marriage, polygamy etc.
Young Bengal followed classical economics, and was composed of free traders who
took inspiration from Jeremy Bentham, Adam Smith, and David Ricardo.
They were passionate advocates of women’s rights and
demanded education for them.
He was dismissed from the Hindu College in
1831 because of his radical views, and shortly afterwards he died of
Cholera at the young age of 22.
Derozians
carried forward Rammohan’s tradition of educating the people in social, economic
and political questions through newspapers, pamphlets and public
associations. They carried on public agitation on public questions such as
the revision of the Company’s Charter, the Freedom of the Press, better treatment for Indian
labour in British colonies abroad, Trial by Jury, Protection of the Ryots
from oppressive Zamindars, and Employment of Indians in the higher grades
of government services.
Why they didn’t succeed?
Social conditions were not yet ripe for their
ideas to flourish. The common
people , who were not acquainted with those ideologies, considered
those young as arrogant.
Their total faith in the British and in
English education,
their rationalism and scientism derived from the west, set
them apart from the masses of Indians and they never succeeded in
organising any social movement in support of their proposed reforms.
Book by Derozio (GK for prelims)
To India – My Native Land
In this , he wrote about pain given by British rule
Debendranath Tagore
He was son of Dwarkanath
Tagore , father of Rabindra Nath Tagore and a close friend of Raja Ram
Mohan Roy .
In
1839 , he started Tattvabodhini Sabha to disseminate the knowledge of the Upanishads
Tattvabodhini Patrika
was the principal organ of the Sabha to propagate the ideas .
After death of Raja Rammohan
Roy, he became the main organiser of Brahmo Samaj.
In
1850 , he wrote book
called Brahmo
Dharma where he
Emphasised on monotheism
Supported rationality and
reject scriptural infallibility
Rejected Caste distinctions
and idolatry
Inspired his sons into reform movement ,most
famous being Rabindranath Tagore
He was part of Landholders Society and played important role in formation of British India Association
IC Vidyasagar
Introduction
His original name was
Ishwarachandra Bandopadhyay.
He was born on 26 September
1820 in the Paschim Midnapore District of West Bengal to impoverished Brahmin
parents.
During the period from 1829 to 1841, Ishwar Chandra
studied Vedanta, Vyakaran, Literature, Rhetorics, Smriti and Ethics in Sanskrit
College. And in 1839 the title ‘Vidyasagar’ was
conferred on him for his unusual talent.
In
1841, at the age of
twenty one years, Ishwar Chandra joined the Fort William College
as a head of the Sanskrit department. In 1851 , Vidyasagar became a professor and later on the
Principal of the Sanskrit College
Works toward Education
He firmly believed that the
regeneration of India was possible only through education.
His work was aimed at
extending the benefits of learning to common people. He stressed upon
instruction through vernacular language.
He
also opened the doors
of the colleges and other educational institutions to lower caste students,
which was earlier reserved only for the Brahmins. For his immense
generosity and kind-heartedness, people started addressing him as “Daya Sagar”
(ocean of kindness).
Having
spent his early life in village Ishwar Chandra could realize the sorrowful
condition of the womenfolk. He rightly believed that the emancipation of women
was not possible as long as they remained ignorant. Ishwar Chandra,
therefore, took
upon himself the task of promoting the cause of female education.
Pioneer in the women upliftment
Started girls schools in Bombay and Calcutta
Encouraged women to study in
the colleges
He also collaborated with Drinkwater Bethune in
establishing the Hindu Female School (at present known as Bethune School and College) in
1849.
Took
initiative in pushing the Widow Remarriage Act ,1856
Instrumental
in passing the Special Marriages Act of 1872.
Wrote book for women
emancipation titled BAHUVIVAH
Social Reforms
He initiated the concept of
widow remarriage and raised concern for the abolition of child-marriage
and polygamy. He demonstrated that the system of polygamy was not sanctioned by the ancient Hindu
Shastras.
He took the
initiative in proposing and pushing The
Hindu Widow Remarriage Act XV of 1856 in India during
Governor-Generalship Lord Canning.
Bengali Connoisseur
He brought a revolution in the education system of Bengal. In his book, “Barno-Porichoy” (Introduction to the letter), Vidyasagar refined the Bengali language and made it accessible to the common strata of the society.
Vidyasagar invented Bengali prose through translation as well as own writings.
Social Reform Movements in western India
Main reform movements in western India were as follows :-
Paramhans Mandali / Samaj
It was started in 1849
By Dadoba
Pandurang . Other
important leader was (Lokhitwadi)
Gopal Hari Deshmukh
It was first socio religious
movement of Maharashtra
Paramhansa Sabha’s principal
objective was the demolition of all
caste distinctions. Each new recruit to the Sabha had to undergo initiation ceremony, and take the pledge that he
would not observe any caste distinctions. He had to eat a slice of bread
baked by a Christian and drink water at the hands of a Muslim.
The Sabha was, however, a secret society; its meetings were conducted in the strictest
secrecy for fear of facing the wrath of the orthodox. The challenge to the
caste system and other social evils thus remained limited
to the participation of its few members only.
Prarthana Samaj
Paramhans Mandali’s
transformation into Prarthana Samaj was the direct consequence of two visits of
KC Sen to Bombay in 1864 & 1867
It was founded by Atmaram
Pandurang in 1867 inspired from the Brahmo Samaj & the main spirit
behind formation was MG Ranade who was ably assisted by KT. Telang
& Bhandarkar
All leading members
were Western educated Maratha Chitpavan Brahmins .
It’s ideology
was almost similar to
Brahmo Samaj
Preached Monotheism
Denounced
idolatry & priestly domination
Denounced
caste distinctions
Favoured Widow Remarriage
& raising age of marriage for both males & females .
Later they
connected themselves with Maharshtrian Bhakti Tradition .
Prarthana Samaj maintained
distinction from Brahmo Movement of Bengal & the most notable
distinction was they were moderate
& more accommodative. They didn’t signal a sharp break & this
gradualist approach made it more acceptable
It’s branches were opened in
Surat, Ahmedabad , Poona & reached even in South India where leader
was Veerasalingum Pantulu
It faced crisis in 1875 when
Swami Dayanand visited Gujarat & Maharashtra & offered
possibilities of a more radical & self assertive religious program
. A group of Samaj members under SP
Kelkar broke
& felt attracted to Arya Samaji ideology of Dayanand .
Side Topic : MG Ranade
He
was co-founder of Prarthana Samaj
He was a product of
the Elphinstone College, Bombay & was Judge of the Bombay High Court during 1891-
1901.
He held that the caste distinction was the main blot on Indian social system.
Under his guidance the
Paramhans Sabha was reorganised in 1867 under the name Prarthana
Samaj.
He was the founding
member of Indian National Congress , member of Bombay Legislative Council and
founding member of Indian
Social Conference (1887)
He was the editor of the Anglo
Marathi paper – Induprakash
Jyotirao Phule and Satyashodak Samaj
He was from Satara ,
Maharashtra
In 1873, Phule established the Satyashodhak Samaj, an organization for challenging Brahmanic supremacy.
He promoted women education along with his wife
Savitribai Jyotirao Phule by
opening women schools.
He also worked for widow
remarriage and to prevent female infanticide, he opened homes for newborn
infants.
He wrote book titled GULAMGIRI
Ideology of Satyashodak Samaj
It was against untouchability & caste system
It opposed idolatry and Brahmin’s role as intermediary between person
and god
Promotion of rational thinking
It also rejected Vedic
supremacy
Servants of India Society
Started by Gopal Krishna Gokhale in 1905
Aims
Create a
band of dedicated workers for nation building
Carry out
activities for the upliftment of Indians
Sri Narayan Guru & SNDP Yogam
Sri Narayan Guru was social
reformer born in 1854 in Kerala into
Ezhava family
He championed
bhakti for spiritual freedom
social equality
rejected casteism
Rejected divisiveness based on caste, religion etc
He was a pioneer reformer who rejected the caste system and stressed on the equality of man. He gave the universal message, “One caste, one religion, one God”
He was influenced by Vedanta.
He supported Temple entry movements.
Sri Narayana Guru condemned animal sacrifice
He urged the Ezhavas to leave the toddy tapping profession and even to stop drinking liquor.
Dr. Palpu, a devotee of Guru established the Sree
Narayana Dharma Paripalana Yogam (SNDP Yogam) in 1903 to further Narayana Guru’s message
This article deals with ‘Karst Topography.’ This is part of our series on ‘Geography’ which is an important pillar of the GS-1 syllabus. For more articles, you can click here.
Introduction
Limestone is a sedimentary rock of organic origin. Chemically it is Calcium Carbonate (but where Magnesium is also present, it is known as Dolomite).
Limestone is soluble in rainwater with Carbon dioxide (weak acid.)
A region with a large stretch of limestone, therefore, posses a very distinct topography termed Karst (name derived from Karst District of Yugoslavia where such topography is particularly well developed)
There is the absence of surface drainage as most of the surface water goes underground and form underground channels. When this water meets non-porous rocks, it re-emerges onto the surface as a spring or resurgence.
Location
Karst region is in Dinarik Alps in Yugoslavia.
Such topography is also found in regions of the Himalayas, Rockies, Andes, Atlas, Shan Plateau, Belo Horizonte etc.
In India, this is found in Chirapoonji, Jammu-Kashmir, Himachal Pradesh, Panch Marhi (M.P.), Bastar (Chattisgarh and Coastal areas near Vishakhapatnam.
Landforms
Erosional Landforms
1 . Lapies
Lapies are the irregular grooves and ridges formed when most of the surfaces of limestone are removed by the solution process.
2. Swallow Hole /Sink Holes
A sinkhole is an opening more or less circular at the top and funnel-shaped towards the bottom.
On the surface of limestone, there are numerous small depressions carved out by solution at a point of weakness. Holes size grow through continuous solvent action to form Sink Hole.
3. Limestone Gorge
When the roof of an underground tunnel collapses, a limestone gorge is formed.
4. Karst Window/ Karst fenster
It is a spring that emerges from underground, discharge its water and then abruptly disappears underground through a nearby sinkhole.
5. Doline
Due to high chemical activity on swallow holes, their size and depth increases. Its diameter may extend up to some kilometres and its depth may run up to 100 meters.
It can be cylindrical, conical, bowl or dish-shaped.
The name doline comes from Dolina, the Slovenian word meaning valley.
6. Uvala
Series of smaller sinkholes coalesce into a compound sinkhole is called uvala.
7. Polze
Polje is an elongated basin having a flat floor and steep walls.
It is formed by the coalescence of several sinkholes. The basins often cover 250 square km and may expose “disappearing streams.”
8. Cave
In areas where there are alternating beds of rocks (shales, sandstones, quartzites) with limestones or dolomites in between or in areas where limestones are dense, massive and occurring as thick beds, cave formation is prominent.
Water percolates down through the cracks and joints and moves horizontally along bedding planes. It is along these bedding planes that the limestone dissolves to form wide gaps called caves.
9. Tunnel
Caves having openings at both ends are called tunnels.
Depositional landforms
Where subterranean streams descend to underground passages, the region may be honeycombed with caves
The most important features in limestone caves are Stalactites, Stalagmites and Pillars.
1 . Stalactites
Formed on roof of caves .
As rainwater seeps
through the limestone, the water dissolves Calcium Carbonate in it. When
from roof, water drips down, it leaves behind Calcium Carbonate (CaCO3) forming
Stalactite .
They are thinner, long and pointed.
2. Stalagmite
They are formed on the floor.
All the dripping water has to land somewhere . When a drop finally hits cave floor , it deposits even more Calcite there in unassumed mound .
They are shorter, fatter and more round.
3. Cave Pillars
Over a long time, stalactites hanging from roof is eventually joined to Stalagmite growing from floor to form pillar.
This article deals with ‘Fluvial Landforms.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Introduction
When rain falls , part of it
sinks into ground , some of it is evaporated back into the atmosphere
& rest runs off as rivulets , streams and tributaries of rivers . This running water is potent agent of erosion .
The river performs three types
of work. They are erosion, transportation and deposition.
Materials transported/carried by
river
When a
river flows , it carries
eroded material in four forms
Solution – Material dissolved in water.
Suspension – Sand, Silt & mud carried in suspended form.
Saltation: Some of the fragments of the rocks move along the bed
of a stream by bouncing continuously.
Traction Load – This includes coarser materials such as pebbles , stones & boulders which are rolled along river bed .
Rivers
carry great amount of material => Eg : Mississippi river removes 2 million tons to Gulf
of Mexico daily .
River Erosion
In rivers, erosion comprise of following processes :-
Corrasion / Abrasion : Mechanical grinding by
river’s traction load against banks & beds of river .
Lateral Corrasion : sideways
erosion which widens V-Shaped
valley.
Vertical Corrasion : downward
action which deepens the river channel.
Corrosion
or Solution : chemical action of water on soluble
or partly soluble rocks. Eg Calcium Carbonate in limestone is dissolved & removed in solution .
Attrition : This is wear and tear of transported material
themselves when
they collide against one
another.
Hydraulic
Action
: This refers to mechanical action
of water. Eg when water splashes against river banks , surges into cracks
& disintegrate the rocks .
River deposition
When the velocity of the stream decreases, the stream
deposits sand, silt
and other fragments
When a river moves in a gentle
slope, its speed reduces and river begins to deposit its load.
The river starts depositing
larger materials first and smaller and finer materials are carried further
down to the mouth of the river.
Course of a River
Upper or Mountain Course /Youthful Stage
In this stage
Predominant Work = Erosion
Predominant action = vertical
corrasion.
Landforms formed in this stage
1. Valleys
1.1 V-Shaped Valley
In upper course, vertical corrasion is at work . Downward
cutting takes place so rapidly that lateral corrasion can’t keep pace. After some time, the
loosened material slowly creeps downward and takes shape of V.
The valley thus developed is
deep , narrow & distinctively V-Shaped.
1.2 Gorges / I-shaped Valley
In some cases, rocks are very resistant and hence afterward loosening don’t take place (because of resistant rock). The valley formed is so narrow & sides are so steep that gorges are formed .
Eg : Indus Gorge in Kashmir .
1. 3 Canyons
Canyons are extended form of
gorges.
In arid regions, where there
is little to widen the valley sides and river cuts deep into the valley
floors , precipitous valleys called Canyons are formed.
Eg Grand Canyon of Colorado
river in Arizona state of USA .
2. Falls
2.1 Rapids
These can form in any part of
river course but are more numerous in mountain
course.
They are formed when there are different layers of hard
rock and soft rocks
. Due to unequal resistance of hard & soft rocks , there is unequal
erosion of both set of rocks . The hard rocks will make river to jump and
fall down
2.2 Cataract
Falls similar to rapids but of
greater dimensions are referred to as Cataracts.
There are 5 along the Nile
that interrupt the smooth navigation.
2.3 Waterfalls
When rivers plunge down in a
sudden fall of some height , they are known as waterfalls. Their force
usually wears out a plunge pool beneath .
They can be formed in various
ways
When a bar of resistant rock
lies transversely across a river valley . Eg Niagara Falls in US
At fault line across river. Eg Victoria falls
on River Zambezi
When river plunges down the edge of a plateau like River Congo .
3. Entrenched /Incised Meanders
These are formed when downcutting process is slow & river cause lateral
erosion leading
to asymmetric valley formation .
Note : These are different
from meanders which occur due to both erosion and deposition. In this,
only erosion takes place.
Middle or Valley Course /Mature Stage
In Middle Course,
In Middle Course, Erosion , Transportation and deposition is done
by the river .
But amount of erosion is very lower
than Youthful stage and in that too, Lateral Corrasion tends to replace vertical corrasion.
The volume of the water
increases with the confluence of many tributaries & this increases the river’s load.
Predominant work of the river = predominantly transportation with some deposition (main deposition happen in Oldage
Stage).
Landforms formed in Middle Stage
1 . Alluvial Fans
Alluvial fans are formed when streams flowing from
higher levels break into foot slope plains of low gradient. Normally very
coarse load is carried by streams flowing over mountain slopes. This load
becomes too heavy for the streams to be carried over gentler gradients and gets dumped and spread as
a broad low to high cone shaped deposit called alluvial fan.
Examples : Alluvial fans are found in
Kosi river when it enters Bihar just after exiting Himalayas
2. Alluvial Cone
As the velocity of river
decreases, its transportation capacity also decreases. Due to this decline
deposition starts in Foot Hills. This deposition forms Alluvial Cones.
It is same as alluvial fan but
slope is more (between 10 to 50 degree)
3. Flood Plains
Rivers in their course carry
large quantities of sediments . During annual or sporadic floods, these
materials are spread over the low lying adjacent areas.
A layer of sediment is thus
deposited during each flood , gradually building up a fertile flood plain.
4. Levees
With the continuous deposition
of soil on the banks by the river, the level of banks rises and they look
like natural dams known as levees .
During flooding as the water
spills over the bank, the velocity of the water comes down and large sized
and high specific gravity materials get dumped in the immediate vicinity
of the bank as ridges. They are high nearer the banks and slope gently
away from the river
Lower or Plain Course /Old Age stage
In Lower/Oldage Course,
River moving
downstream across a broad and level plain is heavy with debris brought down from
the upper course . Hence, work of the river is mainly
deposition, building up its bed & forming extensive flood plains.
Vertical corrasion has almost
ceased though some lateral corrasion still goes on to erode its bank (like
in Meanders).
Landforms formed in Later Stage
1 . Meanders
A meander is a winding curve
or bend in a river.
Meanders are the result of
both erosional and depositional processes.(explained in diagram below)
The irregularities of the ground , force the river to swing in
loops. Once the channel begins to
flow in sinusoidal path , the amplitude
& concavity of loop increases rapidly due to dense erosion occurring
at the outside and deposition occurring inside .
Note : Meanders can be found in Middle as
well as Later Stage
2. Ox-bow Lakes
An oxbow lake is U-shaped body
of water that forms when a wide meander
from the main stream of river is cut off creating free standing body of
water.
It has different nomenclature
at different places – Billabong in Australia,
Rasacas in Texas etc
Both meanders and ox bow lakes are formed both in
middle and lower course. Ox Bow is more commonly found in lower course .
3. Braided Streams
A braided stream is one which does not flow in a single definite channel but rather a network of everchanging, branching and reuniting channels.
Thread-like streams of water rejoin and subdivide repeatedly to give a typical braided pattern
4. Delta
When a river reaches the sea ,
the fine material it has not yet
dropped are deposited at its mouth , forming a fan
shaped alluvial area known as Delta .
This alluvial tract is ,
infact , a seaward extension
of the flood plain.
Delta extend sideways and
seaward at an amazing rate . The River Po extends its delta by over 40 feet a year
(GK) Ganges Brahmaputra delta
is the largest delta in the world.
Deltas differ in their size , shape , growth & importance. A number of factors such as the rate of sedimentation , the depth of the river & sea bed and character of tides , currents & waves greatly influence formation of Delta.
Different type of Deltas
a. Bird’s foot Delta
Deposited alluvial material divides the river into smaller distributaries. Several distributaries look like the foot of a bird.
Example : Mississippi is example.
b. Arcuate shaped Delta
Delta look fan shaped with numerous distributaries
Examples are Amazon, Ganga & Mekong.
c. Estuarine Delta
When river has
their deltas submerged in coastal waters (mainly due to submerged coast like
India’s western coast) or don’t have much deposition to form delta.
Most of India’s west flowing
rivers originating in Western Ghats.
d. Cuspate Delta
Have tooth like projection at
their mouth.
Example : Ebro of Spain.
Conditions favourable for formation of deltas are
Active
vertical & lateral erosion in upper course to provide sediments to be eventually deposited as
Deltas.
The sea adjoining the delta
should be shallow or else the load will disappear in the deep waters.
The coast should be
sheltered, preferably tideless.
There should be no
large lakes in
the river course to filter off the sediments.
There should be no strong
current running at right angle to the river mouth.
Importance of Deltas
a. Ecological importance
Deltas absorb runoff from both floods (from rivers) and
storms (from lakes or the ocean), filter water and thus reduces the impact
of pollution flowing from upstream.
Deltas are also important wetland habitats. They support extremely diverse and specialized
flora and fauna and are areas of dense forests.
b. Economic importance
Deltas are important places
for trade and commerce, and major ports.
Deltas due to rich
accumulation of silt are fertile
agricultural areas.
World’s largest delta is the Ganges–Brahmaputra delta in India and
Bangladesh, is densely populated
supporting livelihood of millions. Fish, other seafood, and crops such as
rice and tea are leading agricultural products of the delta.
Deltas possess well sorted sand and gravel which is quarried.
Due to their diversity they
are centres of tourism and recreation.
Threat to Deltas
Diversion of water for irrigation
and creation of dams reduce sedimentation, which
can cause delta to erode away.
Climate change and rising sea level – rising sea level flood
deltas bringing in saline water and threatening wetland ecosystem. For
example nearly 31 square miles of Sundarbans have vanished entirely due to
sea level rise.
Use of water upstream can greatly increase
salinity levels as less fresh water flows to meet salty ocean water.
While nearly all deltas have been impacted to some degree by humans,
the Nile Delta and Colorado River Delta are some of the most extreme examples
of ecological devastation
This article deals with ‘Weathering and Mass Movements.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Weathering
Weathering is the action of elements of weather over earth materials to reduce them to fragmental state.
Very little or no motion take place in them & process is in-situ.
There are three major groups of weathering processes :
Chemical
Physical or mechanical
Biological weathering processes.
1. Chemical Weathering
a. Solution
When something is dissolved in water , it is called solution.
b. Hydration
Hydration is the chemical addition of water. Minerals take up water and
expand
Calcium sulphate takes in
water and turns to gypsum, which is more unstable
c. Oxidation & Reduction
Oxidation means a combination
of a mineral with oxygen to form oxides or hydroxides. Eg : Oxidation of iron to form rust
When oxidised minerals are
placed in an environment where oxygen is absent, reduction takes place.
Such conditions exist usually below the water table, in areas of stagnant
water and waterlogged ground.
d. Carbonation
Carbonation leads to dissolution of Carbon Dioxide into water to form Carbonic Acids which will dissolve calcium and magnesium compounds
2. Physical Weathering
Physical Weathering
is the disintegration of rock mainly induced by elements of weather and natural
forces.
Physical
weathering can be further divided into following categories
:-
Gravitational forces such as overburden pressure,
load and shearing stress.
Expansion forces due to temperature
changes => Rocks expand during day and contract during night in arid and semi-arid
regions=> the rocks crack and
eventually splits up.
Exfoliation : Rocks generally heat or
cool more on the surface layers. The alternate changes in temperature
could cause their outer layers to peel off from the main mass of the rock
in concentric layers just as the skin of an onion.
Frost wedging : when water
freezes, it expands. As water expands between the rock wedges expand,
it puts great pressure on rocks resulting in weathering.
Water
pressures
controlled by wetting and drying
3. Biological Weathering
Weathering
due to growth or movement of organisms.
Burrowing &wedging by organisms like earthworms,
termites, rodents etc. => exposing
new surfaces to chemical attack
Human beings by disturbing
vegetation, ploughing and cultivating soils=> this creates new contacts
Plant roots exert great pressure breaking rocks apart.
Importance of Weathering
Ecological Importance
Weathering is the initial
stage in the formation of soil. It breaks down the initial
rock mass into smaller fragments thus preparing the rock material for the
formation of soil.
Trees are able to ‘mine’ essential nutrients such as calcium through their
association with symbiotic mycorrhizae through small pores in the mineral
soil, which is possible only due to weathering.
Erosion, with the aid of
weathering, helps in mass wasting and reduction of relief. This leads to modifications in various landforms.
Economic Importance
It leads to the formation of
various natural resources such as clay used in making bricks.
Placer deposits are formed due to weathering . These placer
deposits are source of rare earth metals, thorium etc
It weakens the rocks, thus facilitating the mining and quarrying activities
Hence, we can say that although weathering is a disintegrating process yet it plays an integral role in sustaining life on earth.
Mass Movement
These movements transfer the mass of rock debris down the
slopes under the direct influence of gravity ( happens only under
influence of gravity & no other geomorphic agent is involved)
Weathering is not a
prerequisite for mass movement although it aids mass movements. Mass
movements are very active over weathered slopes .
Mass Movement can be grouped under two classes
1 . Slow Movement
Creep : Occur on moderately
steep, soil covered slopes.
Movement of materials is extremely slow and imperceptible except
through extended observation.
Solifluction : Slow downslope movement of soil mass saturated with water. Quite common in moist temperate areas
2. Rapid Movement
Mostly prevalent in humid climatic regions with gentle to steep slopes.
Earthflow : Movement of
water-saturated earth materials down hillsides. Arcuate scarps
at heads & accumulation bulge
at the toe are observed in this.
Mudflow : Mudflow is a liquid mass of soil, rock debris and water that moves quickly
down a well defined channel. Mudflow
originating on a volcanic slope is called a lahar.
Debris avalanche : characteristic of humid regions with steep slopes. These are
rapidly churning mass of rock
debris, soil, water, and air that moves down steep slopes. The trapped air
may increase the speed of an avalanche by acting as a cushion between the
debris and the underlying surface. They are much faster and deadlier than
Earthflow & Mudflow
Rock falls : Rock falls occur when pieces of rock break from a
cliff. It may result due to Frost wedging . Accumulation of rock debris at the base of a steep
slope is called talus.
Landslides : Landslides occur when a large piece of rock breaks off
and slides down hill. It can be initiated by heavy rainfall or earthquake.
Slump : Great mass of bed rock moves downward by rotational
slip from a high cliff
Question – Why more Landslides & Debris Avalanches occur in Himalayas compared to Western Ghats?
There are many reasons for
this.
One, the Himalayas are tectonically active.
They are mostly made up of unconsolidated and
semi-consolidated deposits.
The slopes are very steep.
Question : Compared to the Himalayas, the Nilgiris bordering Tamilnadu, Karnataka, Kerala and the Western Ghats along the west coast are relatively tectonically stable and are mostly made up of very hard rocks; but, still, debris avalanches and landslides occur although not as frequently as in the Himalayas, in these hills. Why?
Many slopes are steeper with almost vertical cliffs and escarpments in the Western Ghats and
Nilgiris.
Mechanical
weathering
due to temperature
changes and ranges
is pronounced.
They receive heavy amounts of rainfall over short periods. So, there is almost direct
rock fall quite frequently in these places along with landslides and
debris avalanches.
This article deals with ‘Rocks and Minerals.’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
Minerals
Naturally occurring organic and inorganic substance, having an orderly atomic structure and a definite chemical composition and physical
properties.
Composed of two or more
elements. But, sometimes single element minerals like sulphur, silver,
gold, graphite etc. are found
Magma is the source of almost
all minerals.
Types of Minerals
a. Metallic Minerals
These
minerals contain metals and can be sub-divided into
Precious
Metals
gold, silver, platinum
Ferrous
Metals
iron and other metals often mixed with iron to form various kinds of steel.
Non-Ferrous
Metals
include metals like copper, lead, zinc, tin, aluminium etc.
b. Non-Metallic Minerals
These minerals do not contain
metal content.
Sulphur, phosphates and
nitrates are examples of non-metallic minerals.
Cement is a mixture of
non-metallic minerals.
Rocks
A rock is an aggregate of one or
more minerals.
Rocks do not have definite composition of mineral constituents.
Petrology is the science of
rocks.
The age of the rock is
determined based on Carbon-14 dating.
Type of rocks
a. Igneous Rocks
Igneous rocks (Ignis in Latin
means ‘Fire’) are formed when magma
cools and solidifies.
They are known as primary rocks
Igneous rocks are classified based on texture.
If cooled slowly at great depths : Large grains
Sudden cooling (at the surface) : small grains.
Intermediate cooling : intermediate size of grains .
Granite, gabbro, pegmatite, basalt, volcanic breccia and
tuff are some of the examples of
igneous rocks.
Metamorphic rocks are formed when already consolidated rocks undergo reorganization in structure due to excessive pressure (through the process called Metamorphism)
Igneous and metamorphic rocks together account for 95 percent of the earth while rest 5% are sedimentary rocks.
Rock Cycle
Rocks do
not remain in their original form for long but may undergo transformation. Rock cycle is a continuous process through
which old rocks are transformed into new ones.