Wind Systems

Wind Systems

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 can click 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

  1. If pressure gradient is more, velocity will be more in magnitude because differences in atmospheric pressure produces a force.
  2. 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

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 .
Monsoons

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’
Sea and Land Breezes

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.

Sea and Land Breezes

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

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
Chinook , Fohn , Conda

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
Meridional  Circulations

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
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.
Jetstreams
Jet Streams

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 .
    1. 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.
    2. 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.

Pressure and Pressure Belts

Pressure and  Pressure Belts

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 can click 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.
    1. When temperature of air increases, the air expands and reduces the number of molecules over unit area leading to reduction in pressure.
    2. Similarly, when the temperature falls, the air contracts and the pressure increase.
Atmospheric Pressure

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.
Impact of height on pressure

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.

Distribution of Atmospheric Pressure

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

Pressure Belts of Earth

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 :
    1. Rays of sun fall vertically => High temperature creates low pressure.
    2. 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.
    3. 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’.

Temperature and Heat Budget of Earth

Temperature and Heat Budget of Earth

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 can click 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.
Green House Effect

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

Heat Budget of Earth
Temperature and Heat Budget of 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 .
temperature inversion

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.
temperature inversion
  • 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 
valley inversion
  • 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.
impact of temperature inversion

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.

Urban Heat Island

Composition and Structure of Atmosphere

Composition and Structure of Atmosphere

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 can click 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 :-
Composition of Atmosphere
  • 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
    1. Can be upto 4% by volume in wet tropics
    2. 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
    1. It provides Hygroscopic nuclei around which water vapour condenses to produce clouds .
    2. They absorb  and reflect small amount of radiation rays of sun.

Structure of Atmosphere

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
    1. Temperature decreases with increase in height (reaches  – 60 degree Celsius at tropopause).
    2. 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 
    3. However, due to local reasons, at some places this phenomena reverses also (called Temperature Inversion).
  • Height of Troposphere
    1. on Equator, it is 18 km (gases are heated up and rises upward from strong convectional currents)
    2. on poles, it is 8 km (gases are cold and settles down)
    3. 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
    1. Temperature increases with height (ie from – 60 degree Celsius at start to 0 degree Celsius at Stratopause) .
    2. 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
    1. In this layer, once again, temperature starts decreasing with the increase in altitude
    2. 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
    1. Temperature increases rapidly  with height  .
    2. 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 ?
    1. High energy sun rays  and cosmic rays break atoms of gases in this region .
    1. Molecules become ionised (positive charged ).
    2. 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 .
Magnetosphere

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 earths 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.

External Benchmark System

External Benchmark System

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.

Incomplete Transmission of Rate Cut by Banks

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

How Banks decide their Interest Rate
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.
2019RBI 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)

Benefits?

  • Better transmission of Monetary Policy
  • Better transparency and accountability

Reformist Movements

Reformist Movements

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
Reformist Movements

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  & 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

Social Reforms in India Modern History

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
  • 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

  • Various  peripatetic 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 .
Bengal Renaissance

Raja Rammohan Roy (1772-1833)

Raja Rammohan Roy

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 
    1. Indianisation of services
    2. Trial by jury
    3. Separation of Powers between the executive and the judiciary
    4. Freedom of the Press
    5. Judicial equality between Indians and Europeans
    6. 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
Brahmo Samaj

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
    1. Condemned Sati
    2. Favoured abolition of Purdah System
    3. Discouraged Child Marriages & Polygamy
    4. 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.
    1. Goswami bridged the gap between Brahmoism and the popular religious tradition of Vaishnavism
    2. 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
    1. Marriage of Sen’s minor daughter to Prince of Cooch Bihar
    2. 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
    1. Abolition of the caste system and dowry system
    2. Emancipation of the women
    3. Improving educational system
  • Brahmo Samaj ultimately failed and emerged as sectarian religious order after continuous schisms but nevertheless , its achievements were huge
    1. 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.
    2. 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 the Academic 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

Ishwarachandra 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 :-

Reform Movements in Western India

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 & Bhandarka
  • 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 and SNDP
  • 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

Karst Topography

Karst Topography

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

Karst Topography

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.
Sink Holes

3. Limestone Gorge

  • When the roof of an underground tunnel collapses, a  limestone gorge is formed.
Limestone Gorge

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.
Stalactite

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.
Stalagmite

3. Cave Pillars

  • Over a long time, stalactites hanging from roof is eventually joined to Stalagmite growing from floor to form pillar.
Cave Pillars

Fluvial Landforms

Fluvial Landforms

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

Course of 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 .
Gorge

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 .
Grand Canyon

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 
Rapids

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. 
Incised Meanders

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
Alluvial Fans

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.
Flood Plains

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
Levee

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
Meanders

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 .
Oxbow Lake

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.
Bird Foot Delta

b. Arcuate shaped Delta

  • Delta  look fan shaped with numerous distributaries
  • Examples are Amazon, Ganga & Mekong.
Arcuate Delta

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.
Estuarine Delta

d. Cuspate Delta

  • Have tooth like projection at their mouth.
  • Example : Ebro of Spain.
Cuspate Delta

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

Weathering and Mass Movements

Weathering and Mass Movements

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 :
    1. Chemical
    2. Physical or mechanical
    3. Biological  weathering processes.
Weathering

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
Mass Movement

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.

Rocks and Minerals

Rocks and Minerals

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. 
    1. If cooled slowly at great depths : Large grains  
    2. Sudden cooling (at the surface) :  small grains.
    3. Intermediate  cooling : intermediate size of grains .
  • Granite, gabbro, pegmatite, basalt, volcanic breccia and tuff are some of the examples of igneous rocks.

b. Sedimentary Rocks

  • Formed by lithification of sediments
  • They are also known as detrital rocks
  • Examples : sandstoneshale, loess , chalk, coal , limestone etc

c. Metamorphic Rocks

  • Metamorphic rocks are formed when already consolidated rocks undergo reorganization in structure due to excessive pressure (through the process called Metamorphism)
  • Eg : Gneiss, syenite, slate, schist, marble, quartzite, anthracite, diamond  etc.

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.

Rock Cycle