Paper-1, Booklet-1, Geography

PRESENTS THE KEY TO UPSC MAINS 2019 PAPER 1 Copyright © Aspire IAS All rights are reserved. No part of this document may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior permission of Aspire IAS. 1

INDEX 2

PAST YEAR QUESTIONS Explain the factors responsible for the origin of ocean currents. How do they influence regional climates, fishing and navigation? How far do you agree that the behavior of the Indian monsoon has been changing due to humanizing landscapes? Discuss. Mumbai, Delhi and Kolkata are the three mega cities of the country but the air pollution is much more serious problem in Delhi as compared to the other two. Why is this so? India is well endowed with fresh water resources. Critically examine why it still suffers from water scarcity. The states of Jammu and Kashmir, Himachal Pradesh and Uttarakhand are reaching the limits of their ecological carrying capacity due to tourism. Critically evaluate. Smart cities in India cannot sustain without smart villages. Discuss this statement in the backdrop of rural urban integration. What are the economic significances of discovery of oil in Arctic Sea and its possible environmental consequences?' Most of the unusual climatic happenings are explained as an outcome of the EI-Nino effect. Do you agree? Why are the world's fold mountain systems located along the margins of continents? Bring out the association between the global distribution of fold mountains and the earthquakes and volcanoes. Explain the formation of thousands of islands in Indonesian and Philippines archipelagos. Tropical cyclones are largely confined to South China Sea, Bay of Bengal and Gulf of Mexico. Why? Critically evaluate the various resources of the oceans which can be harnessed to meet the resource crisis in the world. Bring out the relationship between the shrinking Himalayan glaciers and the symptoms of climate change in the Indian sub-continent. 3

Whereas the British planters had developed tea gardens all along the Shivaliks and Lesser Himalayas from Assam to Himachal Pradesh, in effect they did not succeed beyond the Darjeeling area. Explain. Why did the Green Revolution in India virtually by-pass the eastern region despite fertile soil and good availability of water? How does India see its place in the economic space of rising natural resource rich Africa? What do you understand by the theory of 'continental drift'? Discuss the prominent evidences in its support. The recent cyclone on east coast of India was called 'Phailin'. How are the tropical cyclones named across the world? Elaborate. Bring out the causes for the formation of heat islands in the urban habitat of the world. What do you understand by the phenomenon of 'temperature inversion' in meteorology? How does it affect weather and the habitants of the place? Major hot deserts in northern hemisphere are located between 20-30 deg N latitudes and on the western side of the continents. Why? There is no formation of deltas by rivers of the Western Ghats. Why? Do you agree that there is a growing trend of opening new sugar mills in southern States of India? Discuss with justification. Analyze the factors for the highly decentralized cotton textile industry in India. With growing scarcity of fossil fuels, the atomic energy is gaining more and more significance in India. Discuss the availability of raw material required for \"the generation of atomic energy in India and in the world. GUESS PAPER - TOPICS EXPECTED TO BE ASKED IN THIS YEAR‘S EXAM, BASED ON CONTEMPORARY ISSUES AND PAST YEARS‘ PATTERN, HAVE BEEN COVERED IN DETAIL. 4

PHYSICAL GEOGRAPHY 5

CLIMATOLOGY ATMOSPHERE AND TEMPERATURE DISTRIBUTION FIGURE: VERTICAL TEMPERATURE DISTRIBUTION AND LAYERS OF ATMOSPHERE 6

Earth intercepts only one in two billion parts of solar radiation. This intercepted radiation is called Insolation. Earth receives Sun‘s radiation (heat) in the form of short waves which are of electromagnetic nature. The earth absorbs short wave radiation during daytime and reflects back the heat received into space as long-wave radiation during night. Through this give and take, or the heat budget, the earth maintains a constant temperature. The heat energy from the solar radiation is received by the earth through three mechanisms—  Radiation: Heat transfer from one body to another without actual contact or movement. It is possible in relatively emptier space, for instance, from the sun to the earth through space.  Conduction: Heat transfer through matter by molecular activity. Heat transfer in iron and other metals is by conduction. Generally, denser materials like water are good conductors and a lighter medium like air is a bad conductor of heat.  Convection: Transfer of heat energy by actual transfer of matter or substance from one place to another. FACTORS AFFECTING TEMPERATURE DISTRIBUTION  Duration of sunshine and seasons.  Transparency of atmosphere.  Land-sea differential albedo.  Prevailing winds and ocean currents.  Slope aspects and altitude.  Vegetation and soil. 7

FIGURE: HORIZONTAL DISTRIBUTION OF TEMPERATURE SEASONAL DISTRIBUTION OF TEMPERATURE 8

PREVAILING WINDS AND PRESSURE SYSTEMS Wind is the horizontal movement of air. Currents are vertical movement of air. Winds balance uneven distribution of pressure globally. They help in transfer of heat, moisture etc. from one place to another. The pattern of planetary winds depends on:  latitudinal variation of atmospheric heating  emergence of pressure belts and pressure gradient force  the migration of belts following apparent path of the sun  the distribution of continents and oceans  the rotation of earth and coriolis force  frictional force exerted by different physiography like mountains etc. The pattern of the movement of the planetary winds is called the general circulation of the atmosphere. The general circulation of the atmosphere also sets in motion the ocean water circulation which influences the earth‘s climate. Differences in atmospheric pressure generate winds. At the Equator, the sun warms the water and land more than it does the rest of the globe. Warm equatorial air rises higher into the atmosphere and migrates toward the poles. This is a low-pressure system. At the same time, cooler, denser air moves over Earth‘s surface toward the Equator to replace the heated air. This is a high-pressure system. Winds generally blow from high-pressure areas to low-pressure areas. The boundary between these two areas is called a front. The complex relationships between fronts cause different types of wind and weather patterns. Prevailing winds are winds that blow from a single direction over a specific area of the Earth. Areas where prevailing winds meet are called convergence zones. Generally, prevailing winds blow east- west rather than north-south. This happens because Earth‘s rotation generates what is known as the Coriolis effect. The Coriolis effect makes wind systems twist counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. 9

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SECONDARY WINDS These winds change their direction with change in season. Monsoons are the best example of large-scale modification of the planetary wind system. Other examples of periodic winds include cyclones and anticyclones, jet stream and air masses. These winds are primarily the result of unequal distribution of land and water, and the resultant difference in pressure, on a local level. It is the product of Adiabatic Lapse Rate and Diabatic Lapse Rate, and resultant changes in stability. They greatly impact the economy and culture of a place. Monsoon winds also help in reducing the pollution. MONSOON  Monsoons were traditionally explained as land and sea breezes on a large scale. Thus, they were considered a convectional circulation on a giant scale. The monsoons are characterized by seasonal reversal of wind direction.  During summer, the trade winds of southern hemisphere are pulled northwards by an apparent northward movement of the sun and by an intense low pressure core in the north-west of the Indian subcontinent. While crossing the equator, these winds get deflected to their right under the effect of Coriolis force. 11

 These winds now approach the Asian landmass as south-west monsoons. Since they travel a long distance over a vast expanse of water, by the time they reach the south-western coast of India, they are over-saturated with moisture and cause heavy rainfall in India and neighbouring countries.  During winter, these conditions are reversed and a high pressure core is created to the north of the Indian subcontinent. Divergent winds are produced by this anticyclonic movement which travels southwards towards the equator. This movement is enhanced by the apparent southward movement of the sun. These are north-east or winter monsoons which are responsible for some precipitation along the east coast of India.  Outside India, in the eastern Asiatic countries, such as Australia, China and Japan, the winter monsoon is stronger than the summer monsoon. (we will study about monsoons in detail while studying Indian Climate) 12

JET STREAMS Jet streams are the strong air streams present in the upper troposphere, lower stratosphere, and possibly even mesosphere which help to complete the global circulation and characterised by strong vertical and lateral wind shear. They are relatively narrow belts of swift-moving winds having velocity in the range of 100km/hr to 900km/hr.  The temperature gradient from the equator towards the poles, the surface high pressure at the poles and genesis of the circumpolar whirl above the poles caused by tropospheric low pressure are the major causes of the origin of the Jet Streams.  Due to the subsidence of the cool air over the Arctic region, the surface high pressure is intensified while upper air low pressure develops in the upper troposphere.  Because of this phenomenon a cyclonic system of air circulation, whose direction is from west to east in the form of whirl develops around upper tropospheric low pressure and the equatorward meandering part of this upper air circulation is called Jet Stream. Types of Jet Streams SUB-  The sub-tropical jet stream is produced by the earth‟s rotation (Coriolis force) TROPICAL and temperature contrast between tropical and sub – tropical regions. WESTERLY JET  At the equator, the rotation produces greatest velocity in the atmosphere. As a STREAM result, the rising air which spreads out northwards and southwards, moves faster than the latitudes over which it is blowing.  It is deflected to the right in the northern hemisphere and to the left in the southern hemisphere, and at about 30° latitude, it becomes concentrated as the subtropical jet streams.  They originate at the meeting point of Hadley and Ferrel Cell. The immense temperature contrast between two air masses produce a sudden change in the pressure gradient, thus sudden change in the velocity.  On account of permanency of the Hadley cell, this Jetstream remains intense throughout the year although, with the shifting of the pressure belt, its path also shifts North-South.  It is closely connected to the Indian and African summer monsoons. It has a major role in bringing western disturbances to India during the winter season and thus provides crucial rainfall which is vital for Rabi Crop. 13

TROPICAL  There are also major high velocity winds in the lower troposphere called low- EASTERLY level jets. In the tropics, the most prominent of these are the Somali Jet and JET the African Easterly Jet. STREAM  The Tropical Easterly Jetstream is a unique and dominant feature of the northern hemispheric summer over southern Asia and northern Africa. It is found near between 5° and 20°N.  It is fairly persistent in its position, direction, and intensity from June through the beginning of October.  Its establishment and maintenance is not fully understood but it is believed that the jet may be caused by the uniquely high temperatures and heights over the Tibetan Plateau during summer, due to which low pressure (converging) sets up at the surface and relatively higher pressure(diverging) in the upper troposphere. The part of this southward diverging air comes under the impact of Coriolis Effect and it is forced to deflect from east to west leading to the formation of a tropical Jetstream.  It has a relationship with oscillation and shifting of ITCZ (Inter-Tropical Convergence Zone) and Monsoon Trough.  During the onset of winter, it suddenly disappears while its arrival heralds the onset of the South West Monsoon. 14

POLAR  The polar front jet is produced by a temperature difference and is closely related NIGHT JET to the polar front. STREAM  It has a more variable position than the sub-tropical jet. In summer, its position shifts towards the poles and in winter towards the equator.  The jet is strong and continuous in winter.  It greatly influences climates of regions lying close to 60 degree latitude.  It determines the path and speed and intensity of temperate cyclones.  Polar Night Jet Stream help in increasing the intensity of Polar Anticyclone.  They are called polar nights as jet streams are formed in winter nights of 6 months at poles. It is found due to the thermal contrast between sub-polar layers and polar layers, and become westerly due to Coriolis force.  This jet has been found in the stratosphere little below the maximum concentration of ozone thus also known as Stratospheric Jet Stream. 15

SOMALI JET  Among the most well-known of the tropical Lower Level Jets is the Somali Jet, STREAM/ a south-westerly. FINDLATER JET STREAM  The Somali jet occurs during the summer over northern Madagascar and off the coast of Somalia. The jet is most intense from June to August.  It is a major cross-equatorial flow from the southern Indian Ocean to the central Arabian Sea.  Formed due to the unequal heating of continent of Africa and located at a very low height of 3-4 km, since the warm air above the Mozambique Channel produces a horizontal thermal contrast with the cold air from the African Highlands.  It also crosses the equator and becomes south-westerly in direction and due to this reason, it is known as Cross Equatorial Jet Stream.  Helps in the intensification of S-W Monsoon over Indian Subcontinent. 16

POLAR  This jet stream was discovered by Rossby and also known as the primary jet FRONT JET stream. STREAM  Polar front jet streams are associated with Polar Fronts. As Polar cold airmass and warm tropical airmass begin to converge upon the subpolar lows, the warm air is lifted above the cold air and it tries to enter the polar region, while the cold air gradually pushes towards the warm air. The rising warm air due to geostrophic effect becomes westerly and known as Rossby wave. And Polar Front Jet are embedded in the Rossby waves (jet stream lies at the core of westerlies which has the highest speed).  They have an important role in the management of latitudinal heat budget of the earth and it accomplishes it through the creation of various cyclones and anticyclones in the Middle-Latitude.  It plays a very important role in the distribution of precipitation in the middle latitude.  Cyclogenesis in the temperate region is associated with the crest of Polar Front jet and maximum cyclonic rainfall occurs ahead of the trough. These jets also determine the path and movement of Temperate Cyclone. 17

EL NINO, SOUTHERN OSCILLATION AND INDIAN OCEAN DIPOLE El Niño is a climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean. El Nino is the ―warm phase‖ of a larger phenomenon called the El Nino- Southern Oscillation (ENSO). La Nina, the “cool phase” of ENSO, is a pattern that describes the unusual cooling of the region‘s surface waters. El Niño and La Niña are considered the ocean part of ENSO, while the Southern Oscillation is its atmospheric changes. El Niño events occur irregularly at two- to seven-year intervals. However, El Niño is not a regular cycle, or predictable in the sense that ocean tides are. El Niño was recognized by fishers off the coast of Peru as the appearance of unusually warm water. We have no real record of what indigenous Peruvians called the phenomenon, but Spanish immigrants called it El Niño, meaning ―the little boy‖ in Spanish. When capitalized, El Niño means the Christ Child, and was used because the phenomenon often arrived around Christmas. El Niño soon came to describe irregular and intense climate changes rather than just the warming of coastal surface waters. Led by the work of Sir Gilbert Walker in the 1930s, climatologists determined that El Niño occurs simultaneously with the Southern Oscillation. The Southern Oscillation is a change in air pressure over the tropical Pacific Ocean. When coastal waters become warmer in the eastern tropical Pacific (El Niño), the atmospheric pressure above the ocean decreases. Climatologists define these linked phenomena as El Niño-Southern Oscillation (ENSO). Scientists use the Oceanic Nino Index (ONI) to measure deviations from normal sea surface temperatures. El Niño events are indicated by sea surface temperature increases of more than 0.9° Fahrenheit for at least five successive three-month seasons. 18

FIGURE: NORMAL CONDITIONS FIGURE: EL NINO CONDITIONS 19

IMPACTS OF EL NINO El Niño events are defined by their wide-ranging teleconnections. Teleconnections are large-scale, long-lasting climate anomalies or patterns that are related to each other and can affect much of the globe.  Without an upwelling of nutrient-rich cold water, the euphotic zone of the eastern Pacific can no longer support its normally productive coastal ecosystem. Fish populations die or migrate.  El Niño brings droughts to Indonesia and Australia. These droughts threaten the region‘s water supplies, as reservoirs dry and rivers carry less water. Agriculture, which depends on water for irrigation, is threatened.  Convection above warmer surface waters bring increased precipitation. Rainfall increases drastically in Ecuador and northern Peru, contributing to coastal flooding and erosion. Rains and floods may destroy homes, schools, hospitals, and businesses. They also limit transportation and destroy crops.  The eastward movement of oceanic and atmospheric heat sources cause unusually severe winter weather at the higher latitudes of North and South America. Regions as far north as the U.S. states of California and Washington may experience longer, colder winters because of El Niño.  Strong El Niño events contribute to weaker monsoons in India and Southeast Asia. ENSO has even contributed to increased rainfall during the rainy season in sub-Saharan Africa.  Diseases thrive in communities devastated by natural hazards such as flood or drought. El Niño-related flooding is associated with increases in cholera, dengue, and malaria in some parts of the world, while drought can lead to wildfires that produce respiratory problems.  El Niño devastates western South American fertilizer industries. The South American fertilizer industry is driven by the droppings of seabirds, whose population declines during El Niño events due to a reduction in their food source (fish). 20

FIGURE: LINK BETWEEN EL NINO, LA NINA AND SOUTHERN OSCILLATION NEGATIVE SOUTHER POSITIVE SOUTHERN OSCILLATION OSCILLATION Port Darwin (western Pacific Ocean) has greater Tahiti (eastern Pacific Ocean) pressure is greater air pressure than Tahiti (eastern Pacific Ocean). than that of Port Darwin (western Pacific Ocean). Drought conditions in Western Pacific and heavy Drought conditions in Eastern Pacific and good rains in Eastern Pacific. rainfall in Western Pacific (Northern Australia and Indonesia). Bad for Indian Monsoons. Good for Indian Monsoons. 21

 It was discovered in 1999 that just like ENSO was an event in the Pacific Ocean, a similar see-saw ocean-atmosphere system in the Indian Ocean was also at play, named the Indian Ocean Dipole (IOD).  The Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperature between two areas (or poles, hence a dipole) – a western pole in the Arabian Sea (western Indian Ocean) and an eastern pole in the eastern Indian Ocean south of Indonesia. IOD develops in the equatorial region of Indian Ocean from April to May peaking in October.  With a positive IOD, winds over the Indian Ocean blow from east to west (from Bay of Bengal towards Arabian Sea). These results in the Arabian Sea (western Indian Ocean near African Coast) being much warmer and eastern Indian Ocean around Indonesia becoming colder and dry.  In the negative dipole year (negative IOD), reverse happens making Indonesia much warmer and rainier.  It was demonstrated that a positive IOD index often negated the effect of ENSO, resulting in increased Monsoon rains in several ENSO years like the 1983, 1994 and 1997.  Further, it was shown that the two poles of the IOD – the eastern pole (around Indonesia) and the western pole (off the African coast) were independently and cumulatively affecting the quantity of rains for the Monsoon in the Indian subcontinent.  Similar to ENSO, the atmospheric component of the IOD was later discovered and named as Equatorial Indian Ocean Oscillation [EQUINOO]. Oscillation of warm water and atmospheric pressure between Bay of Bengal and Arabian Sea. 22

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CYCLONES BASIS TROPICAL CYCLONE TEMPERATE CYCLONE Origin Thermal origin i.e. it needs atleast 27℃ Dynamic origin, i.e. Coriolis Force and temperature of ocean water to form. movement of air masses are the prime causes. Latitude 10 to 30° N and S latitude 35 to 65 ° N and S latitude, especially in the northern hemisphere. Frontal Absent Frontogenesis and occluded front give rise system to temperate cyclones. Formation Form only on seas having temperature Form on both land and seas. more than or equal to 27°C. Season Seasonal: Late summers (Aug – Oct) Irregular. But few in summers and more in winters. Size Limited to small area. They cover a larger area. Shape Typical size: 100 – 500 kms in diameter. Typical size: 300 – 2000 kms in diameter. Varies with the strength of the cyclone. Varies from region to region. Elliptical Inverted ‗V‘ Rainfall Heavy but does not last beyond a few In a temperate cyclone, rainfall is slow and hours. If the cyclone stays at a place, the continues for many days, sometimes even Wind rainfall may continue for many days. weeks. velocity and Greater destruction due to very high Less destruction due to winds (because winds destruction speed winds, storm surges and torrential are comparatively slower) but more rains. destruction due to flooding. Isobars pressure gradient is steep Isobars are usually ‗V‘ shaped and the pressure gradient is low. Lifetime Doesn‘t last for more than a week Last for 2-3 weeks. Path West to East via Westerlies and Jet Streams. No fixed path of movement. Move away from equator. The movement of Cyclones in Arabian Sea 24

and Bay of Bengal is a little different. Here, these storms are superimposed upon the monsoon circulation of the summer months, and they move in northerly direction along with the monsoon currents. Calm region The center of a tropical cyclone is known as In a temperate cyclone, there is not a single the eye. The wind is calm at the center with place where winds and rains are inactive. Driving no rainfall. force The tropical cyclone derives its energy from The energy of a temperate cyclone depends on the latent heat of condensation, and the the densities of air masses. Jet streams difference in densities of the air masses does and their not contribute to the energy of the cyclone. The temperate cyclones, in contrast, have a role No direct relationship. distinct relationship with upper level air flow Clouds The tropical cyclones exhibit fewer varieties The temperate cyclones show a variety of of clouds – cumulonimbus, nimbostratus, etc. cloud development at various elevations. 25

Impact on Both coasts effected. But east coast is the hot Bring rains to North – West India. The India spot. associated instability is called ‗Western Disturbances‘. 26

TERTIARY WINDS LAND BREEZE AND SEA BREEZE The land and sea absorb and transfer heat differently, because of different albedo. During the day the land heats up faster and becomes warmer than the sea. Therefore, over the land the air rises giving rise to a low pressure area, whereas the sea is relatively cool and the pressure over sea is relatively high. Thus, pressure gradient from sea to land is created and the wind blows from the sea to the land as the sea breeze. In the night the reversal of condition takes place. The land loses heat faster and is cooler than the sea. The pressure gradient is from the land to the sea and hence land breeze results. 27

ANABATIC AND KATABATIC WINDS/ HILL AND VALLEY BREEZE In mountainous regions, during the day the slopes get heated up and the air rises. To fill the resulting gap, the air from the valley blows up the valley. This wind is known as the valley breeze, aka anabatic wind. During the night the slopes get cooled and the dense air descends into the valley as the mountain wind. The cool air, of the high plateaus and ice fields draining into the valley is called katabatic wind. LOCAL WINDS 28

LOO  In the plains of northern India and Pakistan, sometimes a very hot and dry FOEHN WINDS wind blows from the west in the months of May and June, usually in the afternoons. It is known as loo. Its temperature invariably ranges between 45°C and 50°C. It may cause sunstroke to people.  Foehn is a hot wind of local importance in the Alps. It is a strong, gusty, dry and warm wind which develops on the leeward side of a mountain range. As the windward side takes away whatever moisture there is in the incoming wind in the form of orographic precipitation, the air that descends on the leeward side is dry and warm (Katabatic Wind).  The temperature of the wind varies between 15°C and 20°C. The wind helps animal grazing by melting snow and aids the ripening of grapes. 29

CHINOOK  Foehn-like winds in USA and Canada move down the west slopes of MISTRAL the Rockies and are known as Chinook winds. SIROCCO  It is beneficial to ranchers east of the Rockies as it keeps the grasslands clear of snow during much of the winter.  Mistral is one of the local names given to such winds that blow from the Alps over France towards the Mediterranean Sea.  It is channelled through the Rhine valley. It is very cold and dry with a high speed.  It brings blizzards into southern France.  Sirocco is a Mediterranean wind that comes from the Sahara and reaches hurricane speeds in North Africa and Southern Europe.  It arises from a warm, dry, tropical air mass that is pulled northward by low- pressure cells moving eastward across the Mediterranean Sea, with the wind originating in the Arabian or Sahara deserts. The hotter, drier continental air mixes with the cooler, wetter air of the maritime cyclone, and the counter- clockwise circulation of the low propels the mixed air across the southern coasts of Europe.  The Sirocco causes dusty dry conditions along the northern coast of Africa, storms in the Mediterranean Sea, and cool wet weather in Europe. 30

TYPES OF CLIMATE The world has several climatic zones but geographers defined the climatic regions based on maximum and minimum temperatures and the temperature range as well as the total and seasonal distribution of precipitation for better understanding. The major climatic regions of the world are discussed below: 1. Equatorial Climatic Region (100 N to 100 S) It is found between 5° and 10° north and south of the equator. This region gets heavy precipitation which is between 150 cm/year. Due to the great heat, the mornings are bright and sunny and evening receive convectional rainfall. Thunder lightning often accompanies the torrential showers. This region is well known for natural rubber called hevea brasiliensis. Amazon basin (South America), Zaire Basin (Africa) especially in western part, and South East Asia (mainly islands) are three well defined regions of this category. 2. The Savana or Sudan Climate (100 to 200 N and S) It is a transitional type of climate found between the equatorial forests and the trade wind hot deserts. It is confined within the tropics and is best developed in the Sudan where the dry and wet seasons are most distinct, hence its name the Sudan Climate. This climate is characterised by an alternate hot, rainy season and cool, dry season. The prevailing winds of the region are the Trade Winds, which bring rain to the coastal districts. Savanna is grasslands of tropical zone. They are known as natural Zoo of the World. Llanos and Campos in South America; Kano and Salisbury region in Africa; Northern and Central part of Australia are the important region of this category. 3. The Hot Desert and Mid-Latitude Desert Climate (200 to 300 N and S) The aridity of hot desert is mainly due to the effects of off-shore trade winds; hence they are also called trade wind deserts. Sahara (Africa) is the biggest desert and the next biggest is Great Australian desert. It is found between 200 to 300 N and S. Hot deserts: Sahara, Australia, Arabian, Iranian, Thar, Kalahari, Namib, Nubian, Mohave (USA), Atacama etc. Cold Desert: Patagonia, Turkestan, Gobi etc. 31

4. The Warm Temperate Western Margin or Mediterranean Climate (300 to 400 N and S) It is a climate that has dry summers that are hot or warm as well as winters that are cool or mild with moderate or high rainfall. It includes the climate of much of the land near the Mediterranean Sea. Outside the Mediterranean, one can find this climate only in rather small areas. It is found in many places that are roughly between latitudes 30° to 40° north and south of the equator. Important Regions are: Coastal region of Mediterranean Sea; Southern Tips of South-west Africa near Cape Town; Southern Australian (in southern Victoria and around Adelaide, bordering the St. Vincent and Spencer Gulfs); South West Australia (Swanland); California around San Francisco; Central Chile in South America. This region is famous for orchard farming e.g. Citrus and fibrous fruits. 5. Temperate Grasslands or Steppe Climate (400 to 550 N and S) It is dry lands due to their position in land masses away from oceanic influences. It is characterised by meagre and unreliable precipitation. The annual range of temperature and rainfall is 13°C and 30 cm. The sub-regions of this climatic region are known by different names in different regions: Steppes (Eurasia); Pustaz (Hungary); Prairies(USA); Pampas (South America- Argentina and Uruguay); Velds (South Africa); Downs(Australia-Murray-Darling basin of southern Australia); Canterbury (New Zealand). 6. Cool Temperate Continental or Taiga or Siberian Climate (550 to 700 N and S) It is characterised by a bitterly cold winter of long duration and a cool brief summer. The average rainfall is 35-60 cm which is quite well distributed through one year with maximum rainfall in summer. This type of climate is experienced in northern hemisphere only because there is no land mass in southern hemisphere. Important regions: Alaska across Canada into Labrador and high Rocky Mountains; Moscow and adjoining belt in Siberia; Central Europe. 7. The Arctic or Polar or Tundra Climate (700 to 900 N and S) It is among Earth's coldest, harshest biomes. The ecosystems of this climatic region are treeless regions found in the Arctic and on the tops of mountains, where the climate is cold and windy and rainfall is scant. The lands of this region are snow-covered for much of the year, until summer brings a burst of wildflowers. 32

8. The Tropical Monsoon and Tropical marine Climate It is also known as a tropical wet climate or trade-wind littoral climate. It is a tropical climate that is primarily influenced by the ocean. It is usually experienced by islands and coastal areas 10° to 20° north and south of the equator. There are two main seasons in a tropical marine climate: the wet season and the dry season. The annual rainfall is 1000 to over 1500 mm (39 to 59 inches). The temperature ranges from 20 °C to 35 °C (68 ° to 95 °F). The trade winds blow all year round and are moist, as they pass over warm seas. These climatic conditions are found, for example, across the Caribbean; the eastern coasts of Brazil, Madagascar and Queensland; and many islands in tropical waters. 33

GEOMORPHOLOGY CONTINENTAL DRIFT THEORY AND RELATED CONCEPTS Various theories were proposed to explain the present location of continents. Continental Drift Theory was the earliest. It was later overshadowed by successful theories like „See Floor Spreading theory‟ and ‗Plate Tectonics‟. CONTINENTAL DRIFT THEORY (ALFRED WEGENER, 1922)  According to Wegener‘s Continental Drift Theory, there existed one big landmass which he called Pangaea which was covered by one big ocean called Panthalassa.  A sea called Tethys divided the Pangaea into two huge landmasses: Laurentia (Laurasia) to the north and Gondwanaland to the south of Tethys.  Drift started around 200 million years ago (Mesozoic Era), and the continents began to break up and drift away from one another.  The drift was in two directions- 1. equator wards due to the interaction of forces of gravity, pole-fleeing force and buoyancy (ship floats in water due to buoyant force offered by water), and 2. westwards due to tidal currents because of the earth‘s motion (earth rotates form west to east, so tidal currents act from east to west.  According to Wegener, the drift is still continuing. 34

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EVIDENCE OF CONTINENTAL DRIFT THEORY 1. Apparent Affinity of Physical Features  South America and Africa seem to fit in with each other, especially, the bulge of Brazil fits into the Gulf of Guinea.  Greenland seems to fit in well with Ellesmere and Baffin islands.  The west coast of India, Madagascar and Africa seem to have been joined.  North and South America on one side and Africa and Europe on the other fit along the mid- Atlantic ridge.  The Caledonian and Hercynian mountains of Europe and the Appalachians of USA seem to be one continuous series. 36

2. Distribution of Fossils  The observations that Lemurs occur in India, Madagascar and Africa led some to consider a contiguous landmass ―Lemuria‖ linking these three landmasses.  Mesosaurus was a small reptile adapted to shallow brackish water. The skeletons of these are found only in South Africa and Iraver formations of Brazil. The two localities presently are 4,800 km apart with an ocean in between them. 3. Botanical Evidence  Presence of glossopteris vegetation in carboniferous rocks of India, Australia, South Africa, Falkland Islands (Overseas territory of UK), Antarctica, etc. can be explained on the basis of the fact that parts were linked in the past. 4. Rocks of Same Age across the Oceans  The belt of ancient rocks of 2,000 million years from Brazil coast matches with those from western Africa. 5. Placer Deposits  Rich placer deposits of gold are found on the Ghana coast (West Africa) but the source (gold bearing veins) are in Brazil and it is obvious that the gold deposits of the Ghana are derived from the Brazil plateau when the two continents lay side by side. 37

CONVECTIONAL CURRENT THEORY According to Convectional Current Theory, the intense heat generated by radioactive substances in the mantle (100-2900 km below the earth surface) seeks a path to escape, and gives rise to the formation of convention currents in the mantle. Wherever rising limbs of these currents meet, oceanic ridges are formed on the sea floor and wherever the failing limbs meet, trenches are formed. Volcanism and associated earthquakes at plate margins are a direct consequence of convection currents in the mantle. 38

PALEOMAGNETISM  It is the study of the record of the Earth‘s magnetic field in rocks, sediment etc. Paleomagnetic rocks on either side of the submarine ridges provide the most important evidence to the concept of Sea Floor Spreading.  Certain minerals in rocks lock-in a record of the direction and intensity of the magnetic field when they form.  This record provides information on the past behavior of Earth‘s magnetic field and the past location of tectonic plates.  Paleomagnetists led the revival of the continental drift hypothesis and its transformation into plate tectonics.  Paleomagnetic studies of rocks and ocean sediment have demonstrated that the orientation of the earth‘s magnetic field has frequently alternated over geologic time.  Periods of “normal” polarity (i.e., when the north-seeking end of the compass needle points toward the present north magnetic pole, as it does today) have alternated with periods of “reversed” polarity (when the north-seeking end of the compass needle points southward)[I have explained this in detail in the video].  As today‘s magnetic field is close to the earth‘s rotational axis, continental drift could be tested by ascertaining the magnetic characteristics of ancient rocks. 39

 Paleomagnetists took a look at the ocean floor going out away from oceanic ridges (either side of the oceanic ridges), they found magnetic stripes that were flipped so that one stripe would be normal polarity and the next reversed.  40

SEA FLOOR SPREADING  The idea that the seafloor itself moves (and carries the continents with it) as it expands from a central axis was proposed by Harry Hess. According to this theory, the intense heat generated by radioactive substances in the mantle (100-2900 km below the earth surface) seeks a path to escape, and gives rise to the formation of convention currents in the mantle.  Wherever rising limbs of these currents meet, oceanic ridges are formed on the sea floor and wherever the failing limbs meet, trenches are formed.  Seafloor spreading is a process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge.  Seafloor spreading helps explain continental drift in the theory of plate tectonics. When oceanic plates diverge, tensional stress causes fractures to occur in the lithosphere.  Older rocks will be found farther away from the spreading zone while younger rocks will be found nearer to the spreading zone. 41

EVIDENCE OF SEA FLOOR SPREADING: 1. Volcanic eruptions are common all along the mid-oceanic ridges and they bring huge amounts of lava to the surface in this area. 2. The rocks equidistant on either sides of the crest of mid-oceanic ridges show remarkable similarities 3. Rocks closer to the mid-oceanic ridges are normal polarity and are the youngest. 4. The age of the rocks increases as one moves away from the crest. 5. The deep trenches have deep-seated earthquake occurrences while in the mid-oceanic ridge areas, the quake foci have shallow depths. 42

PLATE TECTONICS  In 1967, McKenzie and Parker suggested the theory of plate tectonics. The theory was later outlined by Morgan in 1968.  According to the theory of plate tectonics, the earth‘s lithosphere is broken into distinct plates which are floating on a ductile layer called asthenosphere (upper mantle). Plates move horizontally over the asthenosphere as rigid units.  The lithosphere includes the crust and top mantle with its thickness range varying between 5-100 km in oceanic parts and about 200 km in the continental areas.  The oceanic plates contain mainly the Simatic crust and are relatively thinner, while the continental plates contain Sialic material and are relatively thicker.  Lithospheric plates (sometimes called crustal plates, tectonic plates) vary from minor plates to major plates, continental plates (Arabian plate) to oceanic plates (Pacific plate), sometime a combination of both continental and oceanic plates (Indo-Australian plate).  The movement of these crustal plates causes the formation of various landforms and is the principal cause of all earth movements. 43

 Major geomorphological features such as fold and block mountains, mid-oceanic ridges, trenches, volcanism, earthquakes etc. are a direct consequence of interaction between various lithospheric plates.  There are three ways in which the plates interact with each other. FIGURE: DIVERGENT, CONVERGENT AND TRANSFORM BOUNDARY (respectively) 44

MOVEMENT OF THE INDIAN PLATE  India was a large island situated off the Australian coast, in a vast ocean.  The Tethys Sea separated it from the Asian continent till about 225 million years ago.  India is supposed to have started her northward journey about 200 million years ago at the time when Pangaeabroke.  India collided with Asia about 40-50 million years ago causing rapid uplift of the Himalayas.  The positions of India since about 71 million years till the present are shown in the Figure. It also shows the position of the Indian subcontinent and the Eurasian plate.  About 140 million years before the present, the subcontinent was located as south as 50◦ S. latitude. The two major plates were separated by the Tethys Sea and the Tibetan block was closer to the Asiatic landmass.  During the movement of the Indian plate towards the Asiatic plate, a major event that occurred was the outpouring of lava and formation of the Deccan Traps. This started somewhere around 60 million years ago and continued for a long period of time.  Note that the subcontinent was still close to the equator. From 40 million years ago and thereafter, the event of formation of the Himalayas took place.  Scientists believe that the process is still continuing and the height of the Himalayas is rising even to this date. 45

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EARTH MOVEMENTS The configuration of the surface of the earth is largely a product of the processes operating in the interior of the earth. Exogenic as well as endogenic processes are constantly shaping the landscape. The endogenic and exogenic forces causing physical and chemical changes on earth surface are known as geomorphic processes. 47

ENDOGENETIC MOVEMENTS  The interaction of matter and temperature generates these forces or movements inside the earth‘s crust. The earth movements are mainly of two types: diastrophism and the sudden movements.  The energy emanating from within the earth is the main force behind endogenic geomorphic processes. This energy is mostly generated by radioactivity, rotational and tidal friction and primordial heat from the origin of the earth. This energy due to geothermal gradients and heat flow from within induces diastrophism and volcanism in the lithosphere. Diastrophism Diastrophism is the general term applied to slow bending, folding, warping and fracturing. All processes that move, elevate or build up portions of the earth‘s crust come under diastrophism. They include: 1. orogenic processes involving mountain building through severe folding and affecting long and narrow belts of the earth‘s crust. 2. epeirogenic processes involving uplift or warping of large parts of the earth‘s crust. Several places which were on the sea some centuries ago are now a few miles inland. For example, Coringa near the mouth of the Godavari, Kaveripattinam in the Kaveri delta and Korkai on the coast of Thirunelveli, were all flourishing sea ports about 1,000 to 2,000 years ago. Similarly, the Andamans and Nicobars have been isolated from the Arakan coast by submergence of the intervening land. 3. earthquakes involving local relatively minor movements 4. plate tectonics involving horizontal movements of crustal plates. In the process of orogeny, the crust is severely deformed into folds. Due to epeirogeny, there may be simple deformation. Orogeny is a mountain building process whereas epeirogeny is continental building process. Through the processes of orogeny, epeirogeny, earthquakes and plate tectonics, there can be faulting and fracturing of the crust. All these processes cause pressure, volume and temperature changes which in turn induce metamorphism of rocks. 48

Earthquake  It occurs when the surplus accumulated stress in rocks in the earth‘s interior is relieved through the weak zones over the earth‘s surface in the form of kinetic energy of wave motion causing vibrations (at times devastating) on the earth‘s surface. Such movements may result in uplift in coastal areas.  Earthquakes may cause change in contours, change in river courses, ‗tsunamis‘ (seismic waves created in sea by an earthquake, as they are called in Japan) which may cause shoreline changes, spectacular glacial surges (as in Alaska), landslides, soil creeps, mass wasting etc. Volcanoes  Volcanism includes the movement of molten rock (magma) onto or toward the earth‘s surface and also formation of many intrusive and extrusive volcanic forms.  A volcano is formed when the molten magma in the earth‘s interior escapes through the crust by vents and fissures in the crust, accompanied by steam, gases (hydrogen sulphide, sulphur dioxide, hydrogen chloride, carbon dioxide) and pyroclastic material. Depending on chemical composition and viscosity of the lava, a volcano may take various forms. EXOGENETIC MOVEMENTS - DENUDATION  Exogenic (Exogenetic) processes are a direct result of stress induced in earth materials due to various forces that come into existence due to sun‘s heat.  The basic reason that leads to weathering, erosion and deposition is development of stresses in the body of the earth materials. Temperature and precipitation are the two important climatic elements that control various processes by inducing stress in earth materials.  Denudation mainly depends on rock type and its structure that includes folds, faults, orientation and inclination of beds, presence or absence of joints, bedding planes, hardness or softness of constituent minerals, chemical susceptibility of mineral constituents; the permeability or impermeability etc.  The effects of most of the exogenic geomorphic processes are small and slow but will in the long run affect the rocks severely due to continued fatigue. 49

Weathering  Weathering is defined as mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate.  As very little or no motion of materials takes place in weathering, it is an in-situ or on-site process.  There are three major groups of weathering processes: (i) chemical; (ii) physical or mechanical; (iii) biological weathering processes. Significance of weathering  Weathering is the first step in formation of soils.  Weathering of rocks and deposits helps in the enrichment and concentrations of certain valuable ores of iron, manganese, aluminium, copper etc.  Weathering helps in soil enrichment. Without weathering, the concentration of the same valuable material may not be sufficient and economically viable to exploit, process and refine. This is what is called enrichment. 50