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STEP-UP IAS For Notes Q:1 Thunderstorm are severe local storms , which are of short duration, occurring over small area but are violent. Discuss the origin and development of thunderstorm . 12 ½ Marks (200 words) Ans :Origin of Thunderstorm Thunderstorms originate when, an air mass becomes so unstable that it overturns (convicts) violently. Pockets of rising near-surface air in an unstable air mass expand and cool, and as some of the water vapour present condenses into a cloud it releases heat, which then makes the air parcel even warmer, forcing it to rise still higher in the atmosphere. If the lower level air is sufficiently warm and humid, and the higher altitude air is sufficiently cool, this process continues until a tall convective cloud the thunderstorm is formed. For eg : Thunderstorms are most common in the afternoon over land, when daytime heating of the land by the sun causes the lower part of the troposphere to become unstable from higher temperatures and more water vapour in the air. Development of Thunderstorm Most thunderstorms developed by a cycle that has three stages: (1) Cumulus Stage : The sun heats the Earth’s surface during the day. The heat on the surface and warms the air around it. Since A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS (2) (3) For Notes warm air is lighter than cool air, it starts to rise. If the air is moist, then the warm air condenses into a “ cumulus cloud “. The cloud will continue to grow as long as warm air below it continues to rise. Mature Stage : When the cumulus cloud becomes very large, the water in it becomes large and heavy. Raindrops start to fall through the cloud when the rising air can no longer hold them up. Meanwhile, cool dry air starts to enter the cloud. Because cool air is heavier than warm air, it starts to descend in the cloud. The downdraft pulls the heavy water downward, making rain. This cloud has become a “ cumulonimbus cloud “ because it has an updraft, a downdraft, and rain. Thunder and lightning start to occur, as well as heavy rain. Dissipating Stage : After about 30 minutes, the thunderstorm begins to dissipate. This occurs when the downdrafts in the cloud begins to dominate over the updraft. Since warm moist air can no longer rise, cloud droplets can no longer form. The storm dies out with light rain as the cloud disappears from bottom to top. Figure - showing above mentioned developmental stages. Another type of Thunderstorm called “ Super cell thunderstorm “ which are much larger, more powerful, and last for several hours. Q:2 Discuss the Coriolis Force and its significance to Earth climatic phenomena . 12 ½ M (200 words) Ans. Coriolis Force is a phenomenon unique to rotating bodies(Earths bodies) also undergoing translatory motion( Earth‟s revolution). Its of huge climatic significance to Earth as it shapes many climatic phenomenon. It affects the flow of direction of planetary wind system e.g. rightward deflection in Northern Hemisphere, Southward deflection in Southern hemisphere. A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes It leads to flow of jet stream from west to east direction as it deflects the wind rightwards and leads to formation of geostrophic winds. Coriolis force is one of factors for creation of polar vortex conditions in Northern & Southern Hemisphere and is also responsible for circular motion of cyclonic winds e.g. tropical cyclones of bay of bengal, Easterly anti-cyclones over India during summers etc.This happens because it deflects vertical winds towards right/left direction. Coriolis force is also responsible for alternating motion of Ocean Currents. Thus, we can see Coriolis Force is a vital factor that impacts multiple climatic phenomenons and in turn effects human life & other life forms on Earth in more ways than one .for ex: agricultural practices, Indian Monsoons etc. Q.3: What are cyclones? Distinguish between tropical and temperate cyclones. (12 ½ Marks, 200 words) Ans: Cyclones are winds circulating around an area of low pressure. They circulate anti-clockwise in northern hemisphere and clockwise in southern hemisphere. They are categorised by wind speed by Saffir-Simpson scale They are characterized by the following features— A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes 1. Size of tropical cyclones varies considerably. Their diameter ranges between 80 km and 300 km. But sometimes they become so small that their diameter restricted to 50 km or even less. 2. These cyclones affect only the coastal area of the continent. Because these cyclones originate in the ocean and their intensity decreases as they move towards the interior area of continent. 3. The center of the cyclone is having an extremely low pressure and the isobars are circular but fewer in numbers. This is why winds attain a gale velocity. 4. They normally moves from east to west under the influence of trade winds. Difference between tropical and temperate cyclone: • Temperate cyclones are formed in mid latitudes (40-60 degrees north/south), while tropical cyclones are formed in the tropical zone (5-40 degrees north/ south) • Temperate cyclones happen due to convergence of cold and hot air masses and tropical cyclones happen due to convergence of warm dry and warm moist air masses • The isobars of temperate cyclones are wedge shaped or oval shaped, but in tropical cyclones, isobars are circular. Q4 : Discuss the various factor and its impact which involved in ocean acidification. (12 ½ Marks,200 words) Ans The concentration of carbon dioxide gas in the atmosphere is increasing day by day mainly due to activities like burning of fossil fuels, deforestation and production of cement. The carbon dioxide thus released in the atmosphere is absorbed by the oceans which play a very significant role in moderating climate change. When atmospheric carbon dioxide dissolves into the ocean it reacts with water through various steps which ultimately leads to the formation of bicarbonate ions. This causes an increase in the acidity of sea water( lowering pH) A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes Ocean acidification would lead to a reduction in the availability of carbon ions which are essential for carbonate mineral formation(shells, coral reefs). It will also make marine species to experience harmful effects on their health , growth and reproduction processes and to have substantial changes in the habitats and food webs. Reduction in the metabolic rates of jumbo squid, depressed immune response of blue mussels and problems in locating sounds for communication are some of the examples for biological impacts of ocean acidification. Ocean acidification acts as a platform for the destruction of marine food chain, ecosystem and eventually it will accelerate the process of the loss of biodiversity and climatic change. All these negative factors may intern affect the global economy to a great extent. Recent studies show that the current rate of change of ocean acidification is very fast. The steps taken by NOAA(National Oceanic and Atmospheric Administration)show the graveness of the problem and plead for global attention to mitigate the same. Serious and conscious attempts to prevent further ocean acidification is the proper and prompt measure to reduce carbon dioxide emission and to rescue the globe. Q5: Japan experiences much more volcanoes than other countries of the world. Discuss (12 ½ Marks,200 words) Ans: Volcano‟s are places where molten lava comes out vigorously through conduits created by folding/faulting. Japan along with various island arcs and festoons is located in western margin of pacific ocean where Pacific plate collide with Eurasian Plate is susceptible to volcanism .Pacific plate being composed of denser material forced downward to 100 Km where it melts in the form of lava and its volume increases and it has tendency of buoyancy. The molten lava occasionally comes out through weak zones thus making Japan more susceptible to volcanos. Japan‟s origin is a very contested subject among intelligentsia where some suggest it to be of originated due A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes to folding caused by collision of plates whereas others considered it to be volcanic origin due to ejection of molten lava formed due to subduction of Pacific Plate. Occurrence of volcanoes mostly in western margin of Japan suggests it folded origin and since this folding has not squeezed great amount of land mass thus volcanoes find it easier to come out because of least resistance due to lack of high mountains whereas on Eastern Pacific side this tendency is reduced because of lofty Rocky and Andes Mountains. Thus Japan experiences volcanoes much more because of its peculiar origin and it narrow horizontal and vertical expansion. Q6 : In northern hemisphere ,when we go toward 90 degree latitude the length of the day increases in summer seasons .critically examine why the length of day increases and also explain the role of latitude for day and night increase. (12 ½ Marks,200 words) Variation in the length of day and night at different times of the year is because of the revolution of the Earth. Revolution is Earth‟s motion in its elliptical orbit around the Sun at a speed of 18.5 miles per second, one revolution is completed in 365 1/4 days. The axis of the earth is inclined to the plane of the ecliptic at an angle of 66 1/2' giving rise to different seasons and varying lengths of day and night. In summer, the Northern hemisphere is tilted towards the sun. the Rays of the sun fall directly on the Tropic of Cancer. as a result, these areas receive more heat. the areas near the poles receive less heat as the Rays of the sun are slanting. the North Pole is inclined towards the sun and the places beyond the arctic circle experience continuous daylight for about six months so popularly referred to as „Land of the Mid-night Sun‟. since a large Portion of the northern hemisphere is getting light from the sun ,it is summer in the regions north A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes of the equator. the longest day and the shortest night at these places occur on 21st June, is called the summer solstice. Effects of latitude : Latitude of a place on the earth is the angular distance of the place from the equator.1' of latitude is approximately equal to 111 km. Locations on similar latitudes have similar day lengths where as different latitudes have different day lengths. At latitude 0° (the Equator) day length will be approximately 12 hours. Areas on the Equator have a constant 12 hours of day light all year round. Moving away from the Equator As latitude increases to polar circles - north or south-day length can be seen to increase to 24 hours in summer or decrease to zero winter. Q: 7 The circulation of oceanic water originate due to the combined effect of several factors .Discuss the factors like Temperature, salinity and density are the prime causes of oceanic water circulation . (12 ½ Marks,200 words) Ans: An Ocean water circulation has a major impact on the climatic and socio-economic conditions of a country. These circulations are episodic and zonal and are caused due to following factors:- Temperature ,Density and Salinity all are related to each other and causes water to circulate ,they are the initiator of A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes movement of water , This along with other factors like wind direction, Coriolis force ,orientation of land and ocean boundary and gravity causes water to flow in horizontal direction and causes ocean currents. (1) Temperature is the prime force for movement of water .Warm water is lighter and floats over the cool water and causes vertical flow or mixing. when water is warmed it expand and creates a void in which cold and nutrient rich water from bottom of the ocean fills up. Ocean water near the equator receives more insolation and expands up to a level around 8 cm above the mean sea level creating a gradient by which water flows from the equatorial region to pole wards as major surface currents. On the other hand cold water from the Polar Regions sing below the warm surface water and up wells to fill up the vacancy near the equator (2) Salinity Difference: Salinity increases the density of water. Hence oceanic water will flow from the more saline water to the less saline water when the temperature of the regions is same. For example, the current flow from the Atlantic ocean to Mediterranean sea via Gibraltar strait is caused due to salinity difference. (3) Density Difference: As we know that the water move from the low density to higher density. In addition to the temperature and salinity, fresh water influx due to melting of glaciers also changes the density. This addition of fresh water decreases the density of water. East Greenland cold current is supposed to be caused by this reason. (4) Density and salinity is interrelated. : Water with higher salinity have higher density and the vice-versa . water with higher density in heavier and sinks to the bottom .this not only causes the vertical mixing ,with temperature difference between the latitudes causing change in density in the surface level ,water from denser region flows to the less dense regions causing A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes horizontal flow. Apart from these factors precipitation, pressure, and rotation of earth also plays prominent role in driving these currents Hence the oceanic water circulation depends on the factors such as temperature, Salinity and density. One should consider these factors together and not separately. Q:8 Explain the distribution of fold mountains across the world on the context of plate tectonics theory. (12 ½ Marks,200 words) Ans : Fold mountains are the mountains ranges formed due to Collison between the plates I.e convergent plate boundaries. They have been formed and eroded back since the time earths crust was formed. In the present time these fold mountain ranges are present in almost all the continents and mainly 7 major plates are there presentlynorth American, south American, Eurasian, Antarctic, Pacific, indo austral and African. (1) North America: • Rockies- They are tertiary fold mountain range in west coast of north America and were formed due to ocean continental collision between Pacific and American plate. • Appalachian-they are the fold mountain of north America on east coast formed in Caledonian hercynian era when European continent collided with American continent and then they separated. A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes (2) South America: • Andes- fold mountain ranges covering countries Chile, Peru, Ecuador and was formed by o-c between nazca plate and south American plate. (3) Europe: • Alps- also tertiary fold mountains formed by the collision of African and Eurasian plate. (4) Asia: • Himalaya-tertiary Fold Mountains in northern India formed due to Collision of Indian plate with Eurasian plate. • Aravali- eroded mountains that were fold mountain ranges in ancient times formed due to Collision of various Micro plates of Indian subcontinent like singhbhum and aravali plate. (5) Australia: • great dividing range- also an eroded fold mountain range on eastern Australia which was formed due to Collision of Australian plate with Pacific plate (6) Africa: • atlas- fold mountains in north Africa formed by collision of African and Eurasian plate. Q:9 Discuss the factors causing rejuvenation in landscape and describe the resultant landform. (12 ½ Marks, 200 W) Ans: Rejuvenation refers to the increased erosive force of fluvial agents of erosion due to fall in the base level. it is thus brought about by a negative change in the base level and occurs due to following reasons : dynamic : upliftment of landmass, enhancement of slope, fall in the level of the mouth of the river etc ecstatic : fall in sea level due to glaciations, diastrophic changes leading to emergence of coastline, subsidence of ocean bottom etc static : increased volume and flow in river due to river capture, decreased sediment load A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes Rejuvenation pushes back the cycle of erosion to a younger phase and various landforms can be seen depicting a topographic discordance or unconformity of younger forms seen amidst the old often giving rise to multi/polycyclic features 1. Valley in the valley topography : Sudden decrease in sea level or increase the speed of stream causes vertical erosion producing a narrow deep valley under existing a wick shallow valley consisting the pair of terraces about it indicating the end of old valley 2. Uplifted peneplain: When Sea level decreases, a new delta is formed at a lesser height 3. Incised meanders : Stream flowing with high velocity due to steep slope and high kinetic energy. Most of the weight of the stream concentrated in the channel bottom (middle) vertically eroded & producing incised meanders 4. Paired terraces: terraces are usually in valley topography. large number of terraces together called paired terraces 5. Knick Point: Smooth longitudinal profile of a river is disturbed by tectonic hydrological changes, a discontinuity in the profile called Knick point is formed. Q:10 Discuss the concept of cycle of erosion and bring out clearly the difference between the views of Davis and Penck. (12 ½ Marks,200 words) The concept of cycle of erosion deals with the transformation of an uplifted landmass by the process of land sculpture into a featureless plain and strives for explaining what effect can an exogenic force have on the landscape. Different geomorphologists put forward various theories regarding the cycle of erosion. The basic premises of the theory is based on the fact that an uplifted landmass after getting eroded goes through A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 For Notes STEP-UP IAS a cycle of stages as propounded by Morris Davis the whole cycle is divided into three stages viz the youth,the mature and the old stage. Youth stage This is the first stage that starts right after the period of upliftment has culminated The features of this stage are as follows (a) the absolute height of the landforms remains constant (b) relative height of landforms increases due to the valley deepening process done by streaming rivers (c) formation of deep v shaped and i shaped valleys along with features like rapids, cascades, benches are done in this stage (d) valley Deeping is the main phenomenon observed with very little amount of lateral erosion Mature stage (a) (b) (c) (d) (e) the phenomenon of lateral erosion comes into effect vertical erosion ceases to operate both the relative and absolute height of relief decrease the water divide summit start to erode the earlier formed v shaped valleys now start to widen up due to increased volume of river and enhanced rate of abrasion Old stage (a) valley deepening process because of no gradient completely disappears A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes (b) water divide summit erode further by back wasting and down wasting (c) valley becomes flat (d) features like meanders and ox bow lakes are prominent which are formed due to deposition of eroded material (e) resistant rock strata like monad nocks are visible (f) the entire valley becomes a feature less plain called peneplane by william davis (g) old stage is longest of all the stages Difference between the views of Davis and Penck 1. Davis proposed that the process of erosion starts after the endogenic upliftment had concluded whereas; penck believed both upliftment and erosion go side by side 2. according to Davis upliftment period was small but rapid while pencks period of upliftment could be of any length and had differential rates 3. Davis believed that the landform is a function of structure,processa and stage while according to penck landform was largely based on the relationship of rate of upliftment and rate of degradation 4. Davis concept of cycle of erosion was largely time based while pencks concept was time independent 5. Davis concept was focused on humid areas while penck based his theory on the regoins having arid climate Q:11 Discuss the processes of mechanical and chemical weathering and show their relationship with soil formation. (12 ½ Marks,200 words) Ans: Mechanical Weathering Processes: (1) Block disintegration due to temperature: Diurnal changes causes rocks to expand and contract and joints are formed and these rocks than disintegrated A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS (2) (3) (4) (5) (6) For Notes along these joints and broken big block are dislodged from the main rock mass and fall under the impact of gravity, unloading of super incumbent load also helps in this. Granular disintegration due to temperature: This is more active in hot desert here rocks which are of coarse grained and are of different colours they absorb insolation differently and expand and contract differently causing stress inside the rock and they are disintegrated in smaller parts. Block disintegration due to frost: diurnal freeze and thaw cycle causes alternate expansion and contraction which introduce tension and stresses due to which rocks are disintegrated into smaller particles. Exfoilation or onion weathering due to temperature and wind:The outer shells of rocks become loose due to alternate expansion and contraction due to High temperature during day time and comparatively low temperature during night respectively and these loosened shells are removed by strong winds. Disintegration and exfoilation due to unloading: The rocks which are buried under thick covers of of overlaying rocks are disintegrated when they are exposed to the surface when super incumbent load is removed and consequent release of confining pressure. shattering sue to rain shower ans heat: The outer shells of the rocks are shattered due to sudden light showers in hot climatic regions mainly in hot desert areas. Chemical Weathering processes: (1) Solution: This refers to the process of dissolution of soluble particles and minerals from the rocks with the help of water in motion but a thin film of water around a solid particle also leads to chemical dissolution e.g Limestone-calcium carbonate, dolomites -magnesium carbonate etc A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes (2) Oxidation: This refers to the process of oxidation of minerals in presence of water to form mineral oxides like Iron Oxide, these oxides weakens the rock and cause disintegration. (3) Carbonation: carbonation is the reaction of carbonates and bi carbonates with the minerals The rainwater having dissolved the atmospheric CO2 percolates through different horizons of the soils to reach underlying lime stones which in turn cause more organic CO2 to be dissolved and which causes more carbonate rocks and transforming CaCo3 to Ca(HCO3)2. (4) Hydration :The process of hydration is refers to the addition of water to the minerals, this causes volume change and an exothermic reaction which renders minerals to be easily available by the process of carbonation and oxidation. (5) Hydrolysis: Hydrolysis is the process wherein both the mineral of the rocks and water molecules decompose and react in such a way that new minerals are formed. (6) Chelation: This is the form of chemical weathering by plants, plants extact minerals from the soils with the result mineral lattices are disrupted and crystal lattices are fragmented and thus mineral weathering takes place. Physical and chemical weathering are very important processes by which Soil is formed, Big rock are converted into big boulders, cobbles and pebbles, sand an clay. Soil profile is also very much determined by the process involved in weathering Q : 12 Discuss the concept of Volcanism and show how the theory of Plate Tectonics explains the mechanism of volcanism and volcanic eruptions. (12 ½ Marks,200 words) Ans: Volcanism is the process and mechanism through which magma is generated, moved and solidified forming various extrusive and intrusive structures. It is responsible for the formation of oceanic and continental crust, A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes movement of the plates, creation of rock cycle and the formation of various landforms. Landforms crated by volcanism a. Volcanic mountains ex. Mount Kilimanjaro, mount fuziama etc b. archipelagoes ex. Indonesian, Japan c. Various underwater features MOR‟s, seamounts, guyots d. intrusive structures such as batholith, laccolith, sills and dykes. Plate Tectonics Theory and Volcanism:Plate tectonics theory explains volcanism by the mantle convectional cell theory propounded by Arthur homes. It states that due to the interior heat of the earth that is largely primordial heat and also derived by radioactive decay of minerals, at different depth inside the the earth mantle convectional cells set up. some of these cells penetrate the asthenosphere which is weak and in semi molten state and reach earth surface. The viscosity of magma depends on the depth where they generate. They are mafic and fluid if come from lower and middle mantle and form largely extrusive structures. Whereas they are felsic and extremely viscous if comes from upper mantle and subduction zones and form largely intrusive structures. These volcanoes are highly explosive. Volcanism along convergent boundaries- here volcanism is due to the subduction of ocean floor. Since basaltic ocean floor is subducted it forms andesitic lava, it results into the formation of island arcs. Ex. Along pacific ring of fire. Volcanic Eruption is highly explosive along convergent boundaries. Volcanism along divergent boundaries- Here very fluid magma comes from middle and upper mantle and lead to the formation of mid oceanic ridges, sea mounts and guyots. These eruptions are not explosive. A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes Intraplate volcanism- these volcanoes are also called as hotspots. here magma comes from lower mantle and outer core boundary. These are ultra mafic and extremely fluid magma. These magma form Hawaiian type island and flood lava province like deccan trap. Thus the convergent, divergent, transformational plate boundaries are active site for volcanic activity which is conclusively explained by the PTtheory. Q13: What do you understand by ‘continental drift’ theory and the ‘plate tectonics’ theory?. (12 ½ Marks,200 words) Ans:The plate tectonic theory utilising the concept of sea floor spreading and convergent plate boundary phenomenon very well explained the origin and growth of the young fold mountain. Convergent plate boundary can occur between ocean-continental plate and continentcontinent plate. In such interaction the denser plate usually subsides and huge compressional force is generated. In case the plates involved are continental and oceanic plate. On convergence, the heavier plate, usually the oceanic plate subsides under the lighter continental plate. This zone of subduction is called benioff zone. This subduction of heavy plate under the lighter plate cause A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes tremendous compressional force. This compressional force compresses the sedimentary material and pushes them upwards. Thus Fold Mountains are formed. The denser plate which subsides reach deep in mantle melts due to extreme heat and expands in volume. This tends to push the fold mountain even higher thus the upward movement is helped by the melting of the denser plate. Ex : the andes and rockies are formed by convergence of the pacific plate with the south American and north American plates respectively. Continental Drift theory had been proposed by Alfred Wegner in 1912, it talked about distribution of continents and the oceans. According to Wegner all continents used to form a single land mass known as PANGAEA and there was a mega ocean called as PANTHALASSA. However, around 200 million years ago Pangaea began to split into two large land masses called as Lauraisa and Gondwanaland which subsequently broke into many smaller continents.The theory is backed by the following evidences: (1) Jig Saw fit: The Africa and South America continents are almost a perfect fit at 1000 fathom line. (2) Rocks Age: As per the radiometric dating Rocks on the two sides of above mentioned continents are of the same age. (3) Tillite: It‟s a sedimentary rock formed out of deposits of glaciers. The sediments in India have counter parts found in six different landmasses of Southern Hemisphere. (4) Placer Deposits: Ghana have rich placer deposits of gold in spite of having no source rock there but in Brazil. (5) Distribution of Fossils: Plants, animals and fossils have been found to be identical across continents like Africa, Madagascar, India etc. Continental drift theory was a prominent theory for quite some time, however, ocean floor mapping and similar studies post war period changed the view and people moved towards convectional theory and plate tectonic theory etc. A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes Q:14 Discuss the life-cycle of a temperate cyclone and also describe the weather associated with it. (12 ½ Marks,200 words) Ans: Life cycle of the temperate cyclone was proposed by Bjerkens and H Soleberg. it explains the complete cycle from formation to dissipation. Life Cycle The life cycle of temperate cyclone consist of six stages which are: (a) Initial stage of undulating zone called polar front. (b) Beginning of cyclonic circulation. (c) Warm sector well developed. (d) Cold Front overtakes warm front. (e) Occlusion. (f) Dissipation. Between the prevailing westerly‟s and polar easterlies lie a more or less permanent undulating baroclinic zone known as polar front, along which most extra tropical cyclones originate. As the cold air mass pushes under the warm air mass a knick point develops around which cyclonic circulation starts which is anticlockwise. The tongue of advancing equatorial air mass called warm sector has a leading warm front and the lagging cold front at the interface of two air masses. If these air masses neither advances nor retreats, they form a stationary airmass which is for short duration. Eventually the cold front pushes warm sector aloft and the warm sector is occluded by cold front. Associated Weather (a) Warm front: Along the warm front which extends south to south east there is a veering wind shift from anticlockwise to clockwise direction as the front passes, with maximum speed ahead of front. There is a drop of barometric pressure which levels off when the warm front pass. the front is associated with stratified clouds mainly Nimbostratus with light ad A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes widespread rainfall. the visibility becomes poor and there is fog in precipitation area. An appreciable rise in temperature with scattered cumulonimbus clouds is observed when the front passes completely. (b) Cold Front: There is a veering wind shift from anticlockwise to clockwise direction as the cold front passes with rise in barometric pressure. Steep slope of cold front favours the formation of cumulonimbus clouds with associated heavy rainfall and thunderstorms. Once the cold front passes the temperature drops appreciably and there is clear sky with scattered cumulous clouds. Q:15 Discuss the development of local winds, and their influence on local weather, giving three examples of the well-known local winds in the world. (12 ½ Marks,200 words) Ans: Local winds occur on a small spatial scale, their horizontal dimensions typically several tens to a few hundreds of kilometres. They also tend to be short-lived lasting typically several hours to a day. There are many such winds around the world, some of them cold, some warm, some wet, some dry. There are many hazards associated with the winds. The main types of local winds are Sea breezes and land breezes, Anabatic and katabatic winds, and Foehn winds. Katabatic Winds: Katabatic (downslope) winds occur over slopes which are cooled. Katabatic winds occur where air in contact with sloping ground is colder than air at the same level away from the hillside over the valley (see diagram below). Katabatic winds are nocturnal phenomena in most parts of the world (i.e. they tend to happen at night) as there is surface cooling, especially when there is little Katabatic wind speeds do not typically not exceed 3 or 4 m/s. However, where the ground is covered with snow or ice, katabatic winds can occur at any time of day or night with speeds often reaching 10 m/s, or even more if A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes funnelling through narrow valleys occurs. Katabatic winds may lead to the formation of frost, mist and fog in valleys. Sea Breezes: Sea breezes are the result of differential heating of the land and the sea. Sea breezes occur by day, when the land becomes warmer than the sea. Warm air from the land cannot expand into the sea as the air is cooler and more dense, so it expands up into the atmosphere. Cumulus clouds tend to form as the warm air rises over the land to about 500-1500m. The Bise: A cold dry wind which blows from the northeast, north or north-west in the mountainous regions of southeastern France and western Switzerland in winter months. The bise is accompanied by heavy cloud. The Chinook Wind:A warm, westerly wind found in western North America – Canada and the USA, when air from the Pacific blows over the Rocky Mountains and other upland areas. On January 15th, 1972, the Chinook caused the temperature in Lorna, Montana to rise from -48°C to 9°C in 24 hours! The fastest wind speed recorded during a Chinook was 107mph, in Alberta, Canada. The Crachin: The name given to the drizzly weather with low stratus, mist or fog which occurs from time to time during the period January to April over the China Sea and in coastal areas between Shanghai and Cape Cambodia. It occurs when cool, moist air from the north encounters warm, moist air, and it is intensified by orographic lifting and/or by coastal convergence. The Etesians/meltemi: The strong northerly winds which blow at times over the Aegean Sea and eastern parts of the Mediterranean Sea during the period May to October. The winds are known as meltemi in Turkey. The Föhn (or foehn): The Föhn is a warm, dry, gusty wind which occurs over the lower slopes on the lee side (the side which is not directly exposed to wind and weather) of a mountain barrier. It is a result of forcing stable air over a mountain barrier. The onset of a Föhn is generally sudden. For example, the temperature may rise more than 10°C in A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes five minutes and the wind strength increase from almost calm to gale force just as quickly. Föhn winds occur quite often in the Alps (where the name föhn originated) and in the Rockies (where the name chinook is used). They also occur in the Moray Firth and over eastern parts of New Zealand‟s South Island. In addition, they occur over eastern Sri Lanka during the south-west monsoon. Anabatic winds: This wind is caused by thermal (heat) processes. Anabatic (upslope) winds occur over slopes which are heated by the sun. Air which is in contact with slopes that are warmed expands upward and cool and sinks over neighbouring valleys . Anabatic winds are usually slow, at only 1-2m/s and are rarely importance expect near coasts where they can increase the strength of sea breezes. Land breezes :Land breezes occur at night and in the early morning, when the land is cooler than the sea. This is because as the air cools in the night time (as there is less heating from the sun) it contracts. Pressure is higher over the land than the sea. This causes the air to flow from the land to the sea which is known as a land breeze. The circulation is completed by air rising and moving towards the land at 100-300m. Q:16 Define air masses. How do they originate? Classify them and state the characteristics of any one type. (12 ½ Marks,200 words) Ans: Air masses are large bodies of air which have temperature and moisture characteristics nearly the same in the horizontal. The regions where air masses form are referred to as air mass source regions. If air remains over a source region long enough, it will acquire the properties of the surface below. Ideal source regions are regions that are generally flat and of uniform composition. Air masses are classified according to their temperature and moisture characteristics. They are grouped into four categories based on their source region. Air masses that A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes originate in the cold, polar regions are designated with a capital “P” for polar. Air masses that originate in the warm, tropical regions are designated with a capital “T” for tropical. Air masses that originate over land will be dry and are designated with a lowercase “c” for continental. Air masses that originate over water will be moist and are designated with a lowercase “m” for maritime. These letters are combined to indicate the type of air mass: • cP: cold, dry air mass • mP: cold, moist air mass • cT: warm, dry air mass • mT: warm, moist air mass Continental Polar (cP): Continental Polar air masses are also cold to cool and dry, but are not as cold as the Arctic air masses. Continental Polar air masses form over Canada and Siberia. These air masses bring cold air during the winter and cool, relatively clear, rather pleasant weather in the summer. The air mass is stable and usually prevents cloud formation. As the Continental Polar air move south across the warmer land, the lower portion of the air mass may become sufficiently modified by warming to cause a few clouds to form within the air mass. Q :17 Discuss the nature and composition of earth’s atmosphere. (12 ½ Marks,200 words) Ans: Atmosphere is the mixture of different gases & it envelops the earth all around. It contains the life giving gases like Oxygen for humans animals & carbon dioxide for plants. Nature Of Atmosphere :The atmosphere is a deep blanket of gases and suspended liquids and solids that entirely envelops the earth. Compared to the radius of the earth however, the atmosphere is a very thin layer of air. Half the atmosphere lies below a height of 18,000 ft. It is important to note down here , Air is an integral part of the earth‟s mass & 99% of the total mass of the atmosphere is confined to the height of 32 km from the earth‟s surface. A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes Influenced by solar radiation, seasonal temperature and precipitation changes, rotation of the earth, and air/water properties. The atmosphere is structured in layers, including the troposphere, which supports life, and the stratosphere, which contains the protective ozone layer. Composition Of Atmosphere : The atmosphere is composed of gases, water vapour & dust particles. Gases : (1) Nitrogen - 78% - Dilutes oxygen and prevents rapid burning at the earth‟s surface. Living things need it to make proteins. Nitrogen cannot be used directly from the air. The Nitrogen Cycle is nature‟s way of supplying the needed nitrogen for living things. (2) Oxygen - 21% - Used by all living things. Essential for respiration. It is necessary for combustion or burning. (3) Carbon Dioxide - 0.03% - Plants use it to make oxygen. Acts as a blanket and prevents the escape of heat into outer space.It is transparent to the incoming solar radiaton but opaque to outgoing terrestrial radiation. (4) 40 Trace gases - gases found only in very small amounts. They include neon, helium, krypton, and xenon etc. Water Vapour : It is decreases with altitude in warm & wet tropics, it may account four percent of the air by volume, while in dry & cold areas of the desert & polar region, it may be less than one percent of the air. It also absorb parts of the insolation from the sun & preserve the earth radiated heat. water vapour also contributes to the stability & instability in the air. Dust Particles :These are generally concentrated in lower layers of the atmosphere. The higher concentration of dust particles is found in sub -tropical & temperate regions, due to dry wind in comparison to equatorial & Polar Regions. Dust & salt particles act as hygroscopic nuclei around which water vapour condenses to produce cloud A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes Q:18 List the important water bodies and ice caps in news due to changes in the geographical features. Trace the reasons for change. (12 ½ Marks,200 words) Ans Some of the important water and ice bodies in news due to changes are(1) Himalayan glaciers; Have been receding continuously for last few decades and areas earlier covered in ice are now ice free for most of the year. (2) Polar ice caps; Have been shrinking each year, threatening wildlife on one side and opening potentials for resource exploration on the other. (3) Ice free oceans in north Canada; opening a potential sea route around the poles. (4) Aral sea; Due to river diversion had dried up, turning surrounding areas to desert. Has seen limited revival. (5) Dead sea; Has been shrinking due to diversion of River Jordan for irrigation. It already has no life due to high salinity. (6) Tropical oceans are seeing mass bleaching of corals, while corals have expanded beyond their erstwhile habitat due to warming oceans in temperate regions. (7) Rivers worldwide are being polluted, threatening marine life and usability by humans. Ex. Yamuna and Ganga in India and Yangtse in China(missing Baji dolphins). The reasons for these have been abuse of resources by humans. (1) Global warming due to greenhouse gases. (2) Industrial, agricultural, city waste being released into water bodies without treatment. (3) Diversion of water, construction of dams and encroachment on basin areas. Q: 19 How did Perigean moon impact tides around the world and especially in India?discuss the different type of tides and causes of occurrence. (12 ½ Marks,200 words) A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes Ans: Tides is the periodic rise and fall of the oceanic water. It is one of the three primary movements of the ocean water and happens as a result of geometric mean of the gravitational pull of the sun and the moon exerted on the earth. There are two types of tides: (a) (b) Spring tide. Neap tide. Apart from them one more is sometimes considered as tide which is: (c) Sieches Spring Tide: The gravitational pull of the sun and moon act simultaneously, which cause strong high tides. Spring tides generally occur when there is full moon or new moon day. On further classification, when moon is closest to the earth, vis-à-vis Perigean moon, the collective pull increases causing higher rise in sea levels, which is called King tide or Perigean Spring tide. Neap Tide: When sun‟s pull and moon‟s pull are exactly at the right angle then it is called neap tides. These are low tides as the effective gravitational force is least compared to all other positions of the sun and moon. A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes Sieches:These are witnessed as a result of periodic rise and fall of water in enclosed bodies like lakes and bays due to their inherent period of oscillations. Perigean moon Impact On Tide: Perigean moon is a celestial position of moon when it lies closest to the earth. The resultant gravitational pull on oceanic water is maximum producing a bulge that much higher than spring tide. As a result coast around the world witness far greater inundation of water exceeding the high tide level thus demanding the evacuation of marginal coastal areas. In India the Perigean moon tidal bulge is witnessed along the eastern coast of T.N. this combines with the low pressure exhorted oceanic swell and the extra river flow due to monsoon season to produce much higher tide that will inundate vast tracts of the coastal areas Q:20 The greatest concentration of volcanoes is located in the Circum – Pacific region, known as ‘Pacific Ring of Fire’. Examine why and also explain features of these volcanoes. (12 ½ Marks,200 words) Ans :The Pacific “Ring of Fire” is a string of volcanoes and sites located on most of the Earth‟s subduction zones having highseismic activity, or earthquakes, around the edges of the Pacific Ocean. Roughly 90% of all earthquakes occur along the Ring of Fire. Reason for greatest concentration of volcanoes in circum pacific region is the tectonic movement of plates. Tectonic plates are huge slabs of earth crust which fits into each other like pieces of puzzle. They are not fixed and moving atop liquid mantle. Due to this movement at some places they are going apart from each other and some places they are moving toward each other. Former is called divergent boundary and latter is called convergent boundary. At convergent boundary, subduction of tectonic plates results into slipping of heavier plates under lighter plates creating deep trenches. A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178 STEP-UP IAS For Notes As the heavier plates goes inside the mantle, it gets converted into hot magma with gases due to high temperatures. As magma is lighter than mantle, it tends to get outside with pressure through cracks and when this magma comes out it is called lava and such active spots are termed as volcanoes. Similarly at divergent boundary also, magma comes outside through the rifts created by plate movement away from each other. As this activity went on for millions of years , a number of volcanoes were created alongside the boundaries of these tectonic plate known as “Ring of Fire”. Features of these volcano: 1. 2. Many of these volcanoes are very violent and Active, made by basaltic lava which spread over large area. They have created western pacific arcs of volcanic island. Although these arcs are made by volcanic activity but they are not violent. It is argued that here the heavier rock which is subducting, is comparatively softer due to which sudden violent eruptions don‟t occur. A-35/36 (2ND Floor), Bhandari House,Mukherjeenagar,Delhi-9,Phn-011-27659178