Certificate Physical and Human Geography True copy - GC Leong

»1 « - 1 m I i i i *— t i i - A. w. — t * t" - f - r i i y - f 1 - C . hr H . “ . ' L 1 :: - r . * i . i - m i V - - i -r-r- . “ 1 ~ V 7 * • y OXFORD I N D I A / OXFORD I N D I A J WJlllllll ** n u -I * I - 1| H r • + • fi • Li. I l r https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comPreface Part 1 . Physical Geography Part 2. Weather. Climate and Vegetation This second, revised edition carefully follows the recent syllabus. The book is illustrated with maps, diagrams, graphs and photographs. The illustrations have been carefully drawn to assist students in their interpretation of geographical facts presented in the book. Local examples have been quoted wherever possible. Part 2 on world climatic types and natural vegeta¬ tion also includes the economic development of the natural regions. The more important agricultural activities of each region have been treated in greater detail. To assist the student, key words, facts and headings-have been printed in colour. In addition, five questions are included in each chapter. I wish to express my heartfelt thanks to Mr. Khoo Peng Seong B.A.. Dip. Ed., F.R .G.S. for his proof reading, the editiorial staff of O.U.P. for valuable assistance throughout the production of the book and the various authors and friends who have so gene¬ rously helped me. Goh Cheng Leong 56 Jalan Dato Khong Kam Tak Harimau (Tiger Lane) Ipoh Perak Malaysia Acknowledgements The author and publishers are grateful to the following for permission to reproduce copyright photographs: Radio Times.Camera Press.Jabatan Penerangan Malaysia. G.C. Morgan. Philippine Tourist and Travel Association. Paul Popper. Swiss National Tourist Office. J.K. St. Joseph U.S. Information Service, Australian Tourist Commission. Institute of Geological Science. S.T. Fok, N.Z. High Commission Malaysia, Royal Netherlands Meteorological Institute. Meteorologie National Paris. J. Mondaine. Royal Observatory Hong Kong,Government Information Services Hong Kong. Primary' Production Department Singapore, Australian News and Information Bureau. J. Allen Cash. S.E.F. Torino, National Film Board of Canada. Press Information Bureau India. Central Office of Information London. Elizabeth Meyer, Walkabout. Ministry' of Culture Singapore.Standard Triumph. United Nations and Society for Cultural Relations with U.S.S.R. Acknowledgements are credited with their respective reproductions in the book. Every effort has been made to contact the holders of copyright to the reproductions, but in some cases without success.To these, the author and publishers offer their apologies, trusting that they will accept the will for the deed. OXFORD UNIVERSITY PRESS Oxford University Press is a department of the University of Oxford It furthers the University' s objective of excellence in research,scholarship, and education by publishing worldwide. Oxford is a registered trademark of Oxford University Press in the UK and in certain other countries Published in India by Oxford University Press YMCA Library Building. 1Jai Singh Road. New Delhi 110001. India © Oxford University Press 1974 Bangunan Lokc Yew, Kuala Lumpur The moral rights of the author have been asserted First published 1974 43rt impression 2014 All rights reserved. No part of this publication may be reproduced,stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, by licence or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope ol the above should be sent to the Rights Department. Oxford University Press, at the address above You must not circulate this work in any other form and you must impose this same condition on any acquirer ISBN-13: 978-0-19-562816-6 ISBN-10:0-19-5628160 Printed in India by Tara Art Printers Pvt. Ltd.. Noida 201301 Contents Metric Conversion Table v PART I PHYSICAL GEOGRAPHY 1 . The Earth and the Universe 1 Exploring the Universe. 1 : The Solar System, 1 : 'TThe shape of the Earth. 2. Evidence of the Earth' s Sphericity. 2: The Earth' s Movements. 4: Day and Night. 4; The Earth’ s Revolution, 5: Dawn and Twilight. 6; Mathematical Location of Places on the Globe. 7; Latitude. 7; Longitude, 8; Longitude and Time. 8; Standard Time and Time Zones, 9: The International Date Line, 10: Questions and Exercises, 10; Selected Cambridge Questions. 11 . 2. The Earth’ s Crust 12 The Structure of the Earth, 12; The Classification of Rocks, 12; Igneous Rocks, 12 Sedimentary Rocks, 13 Metamorphic Rocks. 13: The Influence of Rock Types on Landscape. 14: Earth Move¬ ments and the Major Landforms, 14; Types of Mountains, 14; Types of Plateaux. 17; Types of Plains, 18. 3. Vulcanism and Earthquakes 20 Landforms Associated with Vulcanic Activities, 20; Landforms of Igneous Intrusions, 20; The Ori ¬ gin of Volcanoes, 21; Types of Volcanoes. 22; Extrusive Landforms, 22; Some Volcanic Erup¬ tions, 23; The Distribution of Volcanoes in the World, 24; Geysers and Hot Springs, 25; Ear¬ thquakes, 26; Some Major Earthquakes, 26: The Distribution of Earthquakes, 26: Questions and Exercises, 26. 4. Weathering, Mass Movement and Groundwater 28 Weathering, 28; Mass Movement, 31; Groundwa¬ ter, 33; The Water-Table, 34; Springs and Wells, 35: Questions and Exercises, 37. 5. Landforms made by Running Water 38 The Development of a River System; 38: The Mechanism of Humid Erosion. 38; The Processes of River Action, 39; River Erosion and Transpor¬ tation, 39; The Course of a River 40; River Rejuvenation, 44; The Human Aspects of Rivers. 45; Questions and Exercises, 45. 6. Landforms of Glaciation 47 The Ice Age and Types of Ice Masses. 47; Landforms of Highland Glaciation, 48; Landforms of Glaciated Lowlands; 51; Human Aspects of Glaciated Landforms, 53, Questions and Exer¬ cises, 54. 7. Arid or Desert I.andforins Types of Deserts, 55; The Mechanism of Arid Ero¬ sion, 56 Landforms of Wind Erosion in Deserts. 57; Landforms of Wind Deposition in Deserts. 59: Landforms due to Water Action in Deserts. 60: Questions and Exercises, 61. 8. Limestone and Chalk Landforms Limestone and Chalk, 62; Characteristic Features of a Karst Region, 62: The Major Limestone Reg¬ ions of the World, 64; Human Activities in Karst Regions, 64: Question and Exercises, 65. 9. Lakes 66 General, 66: The Formation and Origin of Lakes. 66: Lakes and Man, 69; Questions and Exercises. 71 . 10. Coastal Landforms The Action of Waves, Tides and Currents, 72; The Mechanism of Marine Erosion, 72; Coastal Fea¬ tures of Erosion. 73; Coastal Features of Deposi¬ tion. 75; Types of Coasts, 76; Coastlines of Emergence. , 77; Questions and Exercises. 78. 11 . Islands and Coral Reefs 79 General. 79; Coral Reefs. 80; Types of Coral Reefs, 81; The Probable Origin of Coral Reefs. 82; Questions and Exercises 83. 12. The Oceans 84 Exploring the Oceans, 84; The Relief of the Ocean. 85; The Deposits of the Ocean Floor. 86; Salinity of the Ocean. 86; The Temperature of Ocean Water, 86; The Movements of Ocean Cur¬ rents, 87; The Circulation of the Atlantic Ocean. 88; The Circulation of the Pacific Ocean. 89; The Indian Ocean Circulation, 90; Questions and Exercises, 90; Selected Cambridge Questions. 91 . PART 2 WEATHER, CLIMATE AND VEGETATION. 13. Weather 93 T he Difference between Climate and Weather, 93: The Elements of Weather and Climate, 94: Rain ¬ fall, 94; Pressure. 95: Temperature, 96: Humidity. 98; Winds. 98: Sunshine, 99: Clouds, 100; Other Elements Pertaining to Visibility, 104; Questions i and Exercises, 104. I 14. Climate 105 1 The Atmosphere. 105; Insolation. 105; Elements| of Climate and Factors Affecting Them. 106; I Temperature. 106: Factors Influencing Tempera- I i https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comture. 106; Precipitation. 108; Rainfall. 108. Pressure and Planetary Winds. 109; Land and Sea Breezes and Monsoons. Ill; Fohn Wind or Chinook \ in 111; Cyclonic Activity, 112; Climatic Types an Natural Vegetation. 113; W; orld Climatic Types. 114; Questions and Exercises. 115; Selected Cam¬ bridge Questions,115. 15. The Hot, Wet Equatorial Climate * ' 6 Distribution. 116; Climate, 116; Vegetation, 118, Factors Affecting the Development of Equatorial Regions. 119;Questions and Exercises, 120. 16. The Tropical Monsoon and Tropical Marine Climates 122 Distribution, 122; Seasons of the Tropical Mon¬ soon Climate, 123; The Retreating Monsoon. 124; Tropical Marine Climate. 124; Tropical Monsoon Forests, 124; Agricultural Development in Mon¬ soon Lands,125;Question and Exercises, 127. 17. The Savanna or Sudan Climate 129 Distribution, 128; Climate of the Sudan Type. 128; Natural Vegetation. 129; Animal Life of the Savanna. 130; Human Life in the Savanna, 131; Problems, Prospects and Development of the Savanna. 132;Question and Exercises, 133. 18. The Hot Desert and Mid-Latitude Desert Cli¬ mates 134 Distribution, 134; Climate, 134; Climatic Condi¬ tions in the Mid-Latitude Deserts, 136; Desert Vegetation, 136; Life in the Desert, 137; Ques¬ tions and Exercises,140. 19. The Warm Temperate Western Margin (Mediterranean) Climate 141 Distribution, 141; Climate, 141; Natural Vegeta¬ tion, 144; Economic Development of the Mediter¬ ranean Regions, 145; Questions and Exercises, 147. 20. The Temperate Continental (Steppe) Climate 148 Distribution, 148; Climate, 148; Natural Vegeta¬ tion, 150; Economic Development, 151; Questions and Exercises, 153. c 21. The Warm Temperate Eastern Margin (China Type) Climate 155 Distribution, 155; Climate, 155; Natural Vegeta¬ tion, 158; Economic Development, 158; Question and Exercises, 161. 22. The Cool Temperate Western Margin (British Type) Climate 163 Distribution. 163; Climate, 163; Natural Vegeta¬ tion, 165; Economic Development, 165; Questions and Exercises, 169. 23. The Cool Temperate Continental (Siberian) Climate 170 Distribution, 170; Climate, 170; Natural Vegeta¬ tion, 172) Economic Development, 173; Ques¬ tions and Exercises, 175. 24. The Cool Temperate Eastern Margin (Laurentian) Climate 176 Distribution, 176; Climate, 166; Economic Development, 178; Fishing, 179; Questions and Exercises, 181. 25. The Arctic or Polar Climate 183 Distribution, 183; Climate, 183; Tundra Vegeta¬ tion, 184; The Importance and Recent Develop¬ ment of the Arctic Region, 185, Questtions and Exercises, 186; Selected Cambridge Questions, 186. Conversion Scales for Temperature and Rainfall a S -j- 8. 2 s -r :b § ;r 8 8 3cn|ir> II s - ib a ^ s ? :b? S - v- : 8 ? bb ? :j- s ih ? lh:r 8 r- 8 ? 4;j- 2 I— ° a-i :b ? s - ib ? :f St J 8 «t» •: II :r o :r ?* :j-S bb ? •ba H i - — 2 L a I T[ § ? 8 I§ :: II - 8 - 2 8 Jr 8 - : | "•i 1S5 II :L I i-!• §§ :r 2 §§ :r i s o4o-*(0 LL i 1 1 E i £ § 2 ® ® w § JN ^ o II II . § o o r- n II II C0£<1> g iIiII a • 1 1 ST 1II| « S £ r- o Q S ^ s s Tj- ^ rf ID evi CM o c\i3 IIS' II II II II !!!1 - 1 ! II ® 1 I si ? s CMo II «3 1 ! 1 1 CO CM 3 g w 3 II II II 2 B & 2 181 " II H Soo •8 c I1I V 1.0161 metric tons https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comPart 1: Physical Geography Chapter 1 The Earth and the Universe Exploring the Universe On a fine bright night when you look up at the sky it seems to be studded with stars. Little do you realise that each of the stars is far bigger than the earth on which we live. Some of the larger ones have been estimated to be many millions of times the size of the earth. These stars are not scattered regularly in space; they occur in clusters, better described as galaxies or nebulas. Each galaxy may contain as many as 100 million stars. It is believed that the earth’s own galaxy (the Milky Way) alone contains as many as 100,000 million stars. The stars appear small to us even through a telescope because they are so far away. The light from the nearest star travelling at the speed of light (i.e. 186,000 miles per second) takes something like four years to reach us. A ray of light from the sun takes, about eight minutes to reach the earth. Light takes only a second to reach us from the moon. The Solar System The solar system comprises the Sun and its nine planets (Fig. 1.) which are believed to have been developed from the condensation of gases and other lesser bodies. All the planets revolve round the Sun in elliptical orbits. Like the earth, they shine only by the reflected light of the sun. The Sun has a surface temperature of 6,000°C. (10,800°F.) and increases to 20 million°C. (36 million°F.) in the interior. All over its surface are fiery gases that leap up in whirls of glowing flames like a volcano in eruption. In size, the Sun is almost unimaginable. It is about 300,000 times as big as the earth! Amongst the nine planets, Mercury is the smallest and closest to the sun, only 36 million miles away. It thus completes its orbit in a much shorter space of time than does Earth. A year in Mercury is only 88 days. Venus, twice the distance away from the sun, is the next closest planet. It is often con¬ sidered as 'Earth' s twin because of their close proximity in size, mass (weight) and density. But no other planet is in any way comparable to Earth which has life and all the living things we see around us. Like many other planets, the Earth has a natural satellite, the Moon, 238,900 miles away, that revolves eastward around the Earth once in every 27 days. The fourth planet from the sun is Mars which has dark patches on its surface and is believed by most professional astronomers to be the next planet after Earth to have the possibility of some plant life. Much attention has been focused on Mars to explore the possibilities of extending man’s influence to it. Next comes Jupiter, the largest planet in the solar system. Its surface is made up of many gases like hydrogen, helium, and methane. It is dis¬ tinguished from other planets by its circular light and dark bands, and the twelve satellites that circle round it. As it is more than 485 million miles from the Sun, its surface is very cold, probably about -200°F. (-130°C.). S U N . Ostance from tun to planet 1.783,000.000 miln 4,S66.000.000m.le« 485.000.000 mile *-- - 93.000.000 mile * X.000.000 mile * 9"“°" ° Q 4 ^ ° °©° ° ° Cd} oQ° 9 ? MERCURY VENUS I EARTH MARS JUPITER SATURN URANUS PLUTO % 1 The Solar System— the Sun and the nine Planets https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comI Sun that it takes £ " not known to The scventh JdJ^ ’ e la[e eighteenth century w'hen “ L a faint bluish-green disc through it was firs . lescope it is another giant planet. hand .5 limes aS heav, Unlike other planets. Uranus orbits around the sun “ 7 clockwise direction front east to west with five satellites revolving round it. The two outermost planets in the solar system. Neptune and Pluto are just visible with telescopes Their discoveries were the result of mathematical calculations on their irregular gravitational effects on neighbouring planetary bodies. Neptune closely resembles Uranus, except that it has only two known satellites and is probably much colder. Pluto is smaller than Earth. As the orbits of the planets are not circular but elliptical, the distance of Pluto from the Sun during perihelion (i.e. when it is closest to the Sun) is 2,766 million miles, and at aphelion (i.e. when it is farthest from the Sun) is 4,566 million miles. A year in Pluto is no less than 247 years on earth! Due to their very recent discovery and their extreme remoteness from the earth, very little isso far known about these last two planets. The Shape of the Earth In the olden days, sailors feared to venture far into the distant ocean because they thought the earth was as flat as a table. They thought that when they reached the edge of the earth, they would slip down and perish in the bottomless ocean. This is, of course, not true. From years of accumulated know¬ ledge, experience and observations in different parts of the world, we know that the earth is round. Its accepted spherical shape is an established fact, proved, and done by all. There has been so much research have on earth science that its various dimensions been accurately found. It has an equatorial cumference circumference of 24,897 miles and- its polar cir¬ diameter is less by 83 miles. Its equatorial shorter by is 26 7,926 miles miles and its polar diameter is earth is not a . This simply shows that the perfect both ends sphere. It is a little flattened like an orange. It can, in fact, be Evidence of the Earth' s Sphericity There are many ways to prove that the earth js spherical. The following are some of them. 1. Circum-navigation of the earth. The first voyage around the world by Ferdinand Magellan and his crew, from 1519 to 1522 proved beyond doubt that the earth is spherical. No traveller going round the world by land or sea has ever encountered an abrupt edge, over w'hich he would fall. Modern air routes and ocean navigation are based on the assumption that the earth is round (Fig. 2). A CURVED EARTH f EAHTH (spherical) * Fig. 2 (a) Circumnavigation of the earth & 4 DRC (b) Abrupt drop at the edge of a table-like earth 2. The circular horizon. The distant horizon viewed from the deck of a ship at sea, or from a cliff on land is always and everywhere circular in shape. This circular horizon widens with increasing altitude and could only be seen on a spherical body. This is illustrated in Fig. 3. called a geoid (‘ earth-sha^ fft The^ nh “ ** ]' Ship’s visibilitya of the shiP appears over the earth is also masked hv thJ ? h d, lands and oceans stant horizon < the top of the mast is seen first before on its surface m ervenmg blgb' | he hull. In the same way, when it leaves harbour, its disappearance over the curved surface is equally / \ \ / \ / / I v\ HORIZON Fig. 3 (a) Increasing altitude widens the circular hori ¬ zon. Viewed from Y the horizon would be AB but from a higher viewpoint (X) a wider horizon (C, D) would be seen A VIEW POINT / \ / ^ Y VIEWPOINT ^, ^ / \ HOR ZON B (b) Visible horizon remains the same regardless of altitude. If the earth were flat the horizon seen from either Y or X would be the same gradual. If the earth were flat, the entire ship would be seen or obscured all at once. This is apparent from Fig. 4. A CURVED EARTH (t)0S ^ line of sight 4 A SPHERICAL EARTH F ' 9- 4 (a) The mast of a ship is seen before the hull on curved horizon 4 A FLAT EARTH •V ^ 4 A F L A T E A R T H Fig. 4 (b) A flat earth, the entire ship is seen at once on a flat surface 4. Sunrise and sunset. The sun rises and sets at different times in different places. As the earth rotates from west to east, places in the east see the sun earlier than those in the west. If the earth were flat, the whole world would have sun.i e and sunset at the same time. But we know this is not so. Fig. 5 illustrates this. . I , ' - Fig. 5 (a) Sun rises and sun sets at different times for different places (b) The whole world will have sun rise or sun set at the same time 3 https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comT The lunar eclipse. The shadow cast by the earth on the moon during the lunar eclipse is always circular. It takes the outline of an arc of a circle. Only a sphere can cast such a circular shadow. 6. Planetary bodies are spherical. All observations from telescopes reveal that the planetary bodies, the Sun. Moon, satellites and stars have circular outlines from whichever angle you see them. They are strictly spheres. Earth, by analogy, cannot be the only exception. 7. Driving poles on level ground on a curved earth. Engineers when driving poles of equal length at regular intervals on the ground have found that they do not give a perfect horizontal level. The centre pole normally projects slightly above the poles at either end because of the curvature of the earth, as illustrated in Fig. 6. Surveyors and field engineers therefore have to make certain corrections for this inevitable curvature, i.e. 8 inches to the mile. MOW poto prefect* abw ocmn vm* ocji* ««*1 Fig. 6 (a) The centre pole projects well above the poles at either end on a curved surface ST . Sfv ** 2 °** «ths unw fe« POLES - > : f . j * - " have height aUit^ Vr” &PiC:r fr0m curved edge of the earth ^ ^ Sh° W clear|y the convincing and the m » ' S 1S the most Orth’s sphericity ^ UP't0* date P f of the 4 The Earth' s Movement Man is always conscious of the ' apparent movement of the sun and little realizes that the earth on which he stands is constantly in motion. When the sun isappears, he says that the sun sets and when it emerges, e says that the sun rises. He is not the east aware that the sun, in fact, does not rise or set, 11 we who nse and we who set’! The earth moves axk fC& m tW° d*staict ways: it rotates on its own dav W£ / St . t0 CaSt° nce in every 24 hours< causing . •. n ni^. l ’ 11 a ^ so revolves round the sun in an and the " ?urin 365‘ dayS> Causing the seasonS Day and Night Sntf ; 3* V nr V Jp " T» 5so^ ’ r " | K L (Moon) The earth viewed from the moon. The picture was taken on the Apollo 8 mission of 1968 which prepared the way for the moon landing Camera Press the sun and experiences daylight. The other portion which is away from the sun’s rays will be in darkness. As the earth rotates from west to east, every part of the earth’s surface will be brought under the sun at some time or other. A part of the earth’s surface that emerges from darkness into the sun’s rays experiences sunrise. Later, when it is gradually obscured from the sun’s beams it experiences sunset. The sun is, in fact, stationary and it is the earth which rotates. The illusion is exactly the same as when we travel in a fast-moving train. The trees and houses around us appear to move and we feel that the train is stationary. Fig. 7 explains the earth’s rotation and the causes of day and night. The Earth' s Revolution ^ hen the earth revolves round the sun, it spins on an elliptical orbit at a speed of 18.5 miles per second Fig. 7 (a) Kuala Lumpur emerges from darkness into daylight at sun rise when the earth rotates into the sun's rays (b) The sun is directly overhead at Kuala Lumpur or midday (c) Kuala Lumpur passes from daylight into darkness at sunset when the earth rotates away from the sun (d) Kuala Lumpur is directly away from the sun at mid-night or 66,600 m.p.h. One complete revc’ - ution takes 365{ days or a year. As it is not possible to show a quarter of a day in the calendar, a normal year is taken to be 365 days, and an extra day is added every four years as a Leap Year. 1. Varying Lengths of Day and Night The axis of the earth is inclined to the plane of the ecliptic (the plane in which the earth orbits round the sun) at an angle of 663°, giving rise to different seasons and varying lengths of day and night (Fig. 8). If the axis were perpendicular to this plane, all parts of the globe would have equal days and nights at all times of the year, but we know this is not so. In the northern hemisphere in winter (December) as we go northwards, the hours of darkness steadily increase. At the Arctic Circle (664°N.), the sun never ‘rises’ and there is darkness for the whole day in mid-winter on 22 December. Beyond the Arctic Circle the number of days with complete darkness increases, until we reach the North Pole (90°N.) when half the year will have darkness. In the summer (June) conditions are exactly reversed. Daylight increases as we go polewards. At the Arctic Circle, the sun never ‘sets’ at mid-summer (21 June) and there is a complete 24-hour period of continuous daylight. In summer the region north of the Arctic Circle is popularly referred to as ‘Land of the Mid¬ night Sun . At the North Pole, there will be six months of continuous daylight. Fig. 8(a) illustrates the revolution of the earth and its inclination to the plane of the ecliptic which cause the variation in the length of day and night at different times of the year. 5 https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comA»TIAI * CTK:C««CU lOAVtKSHtl Lu , days are termed equinoxes meaning ‘equal n ; , because on these two days all parts of the have equal days and nights. After the iu ° r , ( I equinox the sun appears to move north and js ^ tically overhead at the Tropic of Cancer (23t° xj Ver - about 21 June. This is known as the June or Slul 0 , 1 solstice, when the northern hemisphere wiliu ^ Fig. 8 (a) The revolution of the earth and its efffects on seasons and the varia tions of lengths of day and night Mt, Tropic of Cane* 2 * (b) A simplified diagram showing the annual movement of the sun and the causes of the seasons In the southern hemisphere, the same process ucuuspnere takes place, except that the conditions are reversed. When it is summer in the northern hemisphere, the southern continents will experience winter. Mid¬ summer at the North Pole will be mid-winter at the South Pole. 2. The Altitude of the Midday Sun In the the sun course of a year, the earth’s revolution round with its axis the inclined at 66i° to the plane of ecliptic changes the apparent midday altitude of the equator sun. The sun is vertically overhead at the 21 March on and two days each year. These are usually 21 September because a year though the date changes is not exactlv w - •« solstice, wnen me . ' TT nave Z longest day and shortest night. By about 22 Scember the sun will be overhead at the Tropi, ZTapricorn (23!"S.). This is the wm* r soUUc, when the southern hemisphere will have its longest day and shortest night. The Tropics thus mark the limits of the overhead sun, for beyond these, the sun is never overhead at any time of the year. Such regions are marked by distinct seasonal changes- spring, summer, autumn and winter. Beyond the Arctic Circle (66i°N.) and the Antarctic Circle (66i°S.) where darkness lasts for 6 months and daylight is continuous for the remaining half of the year, it is always cold; for even during the short summer the sun is never high in the sky. Within the tropics, as the midday sun varies very little from its vertical position at noon daily, the four seasons are almost indistinguishable. Days and nights are al¬ most equal all the year round Fig. 8(b). 3. Seasonal Changes and their Effects on Temperature Summer is usually associated with much heat and brightness and winter with cold and darkness. Why should this be so? In summer, the sun is higher in the sky than in winter. When the sun is overhead its rays fall almost vertically on the earth, con¬ centrating its heat on a small area; temperature therefore rises and summers are always warm. In winter the oblique rays of the sun, come through the atmosphere less directly and have much of their heat absorbed by atmospheric impurities and water vapour. The sun’s rays fall faintly and spread over a great area. There is thus little heat, and tem¬ peratures remain low. In addition, days are longer than nights in summer and more heat is received over the longer daylight duration. Nights are shorter and less heat is lost. There is a net gain in total heat received and tem- npratnro — - rightsinwinT * Sh ° rter ^ and longeT mghts m winter account for the reverse effects. Dawn and Twilight The brief period between sunrise ,and full dayl ' g is called dawn, and that ^ between sunset and complex darkness is term<»a — • 6 uiiu Detween sunset and complete darkness is termed twilight. This is caused by the VMr • * , — “ " T Lne aate changes fact that during the periods of dawn and twilight y ar not exactly 365 days. These two the earth receives diffused or refracted light from the sun whilst it is still below the horizon. Since the sun rises and sets in a vertical path at the equator the period during which refracted light is received is short. But in temperate latitudes, the sun rises and sets in an oblique path and the period of refracted light is longer. It is much longer still at the poles, so that the winter darkness is really only twilight most of the time. (Fig. 9). (a) piiiteai !| i l! ' 4 | i Fig. 9 Dawn and Twilight (a) at the equator (b) in temperate latitude A £ night At the equator the sun rises and sets almost vertically so the time it takes to passthrough the 'twilight zone' (A, B) will be shorter than for temperate latitudes where the sun rises and sets obliquely. Here the time taken to pass through the twilight zone (C, D) is longer Mathematical Location of Places on the Globe The earth’s surface is so vast that unless a mathe¬ matical method can be used, it is impossible to locate any place on it. For this reason, imaginary lines have been drawn on the globe. One set running east and west, parallel to the equator, are called lines of latitude. The other set runs north and south passing through the poles and are called lines of longitude (Fig. 10). The intersection of latitude ’. ^ 1 - W © •< > SP. Fig. 10 (a) Parallels of latitude (b) Meridians of longitude and longitude pin-points any place on the earth ' s surface, (Fig. 11c.). For example Delhi is 28°37' N. and 77°10' E.; London is 5r30' N. and O ^ 'W, and Sydney is 33°55 S. and 151°12 E. We shall examine more closely how latitude and longitude are determined and the role they play in mathematical geography. Latitude Latitude is the angular distance of a point on the earth’s surface, measured in degrees from the centre of the earth as shown in Fig. 10(a). It is parallel to a line, the equator, which lies midway between the poles. These lines are therefore called parallels of latitude, and on a globe are actually circles, becoming smaller polewards. The equator represents 0° and the North and South Poles are 90°N. and 90°S. Between these points lines of latitude are drawn at intervals of 1°. For precise location on a map, each degree is sub-divided into 60 minutes and each minute into 60 seconds. The most important lines of latitude are the equator, the Tropic of Cancer (23i°N.), the Tropic of Capricorn (23±°S.), the Arctic Circle (66i°N.) and the Antarctic Circle (66t°S.). As the earth is slightly flattened at the poles, the linear distance of a degree of latitude at the pole is a little longer than that at the equator. For example at the equator (0°) it is 68.704 miles, at 45° it is 69.054 miles and at the poles it is 69.407 miles. The average is taken as 69 miles. This is a useful figure and can be used for calculating distances to any place. Bombay is 18-55° N; it is therefore 18-55 x 69 or 1280 miles from the equator. With the aid of your atlasfind the approximate distance of the follow7 https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comI / h the Royal Astronomical Observatory ai linear dislance each of the 360 degrees of Iongitude is 25 000^ -360 or 69-1 miles. As the parallels 0f latitude become shorter polewards, so the meridians of longitude, which converge at the poles, enclose a narrower space. The degree of longitude therefore decreases in length. It is longest at the equator where it measures 69.172 miles. At 25° it is 62.73 ^ ^ mileS) at 45° it is 49 miles, at 75° 18 miles and at RO n (a) The latitude of 38-N. is the an9ular the poles 0 mile. There is so much difference in distance of a point on the earth's surface north of the the length of degrees of longitude outside the tropics, centre of the earth that they are not used for calculating distances as — !!£ — in the case of latitude. But they have one very important function, they determine local time in relation to G.M.T. or Greenwich Mean Time, which is sometimes referred to as World Time. Longitude and Time Local Time. Since the earth makes one complete revolution of 360° in one day or 24 hours, it passes through 15° in one hour or 1° in 4 minutes. The earth rotates from west to east, so every 15° we go eastwards, local time is advanced by 1 hour. Con¬ versely, if we go westwards, local time is retarded by 1 hour. We may thus conclude that places east of Greenwich see the sun earlier and gain time, whereas places west of Greenwich see the sun later and lose time. If we know G.M.T., to find local time, we merely have to add or subtract the difference in the number of hours from the given longitude, as illustrated below. A simple memory aid for this will be East-Gain-Add ( E.G.A.) and West-LoseSubtract ( W.L.S.). You could coin your own rhymes for the abbreviations. Hence when it is noon, in London (Longitude 0°5W.), the local time for Madras (80°E.) will be 5 hours 20 minutes ahead of London or 5.20 p.m. But the local time for New York (74°W.) will be 4 hours 56 minutes behind London or 7.04 a.m. We can put it in another way, when Londoners are having lunch, Indians will have dinner and New Yorkers will have breakfast. (Fig. 12). This is difficult to believe, but it is true. The rotation of the earth round the sun means that at any point in time different place* will experience a different time of day. There are many ways of determining the longitude of a place. The simplest way is to compare the local time with G.M.T. by listening to B.B.C. radio (b) The longitude of 135°W. is the angula distance west of the Prime Meridian zr fl¬ ic) The precise location of place X is latitude 52°N. and longitude 27°W. where they intersect &P. Longtitude degrees Longitude is an angular distance, measured in (or along the equator east or west of the Prime the globe First) Meridian, as indicated in Fig. 11(b). On that longitude is shown as a series of semi -circles equator run from pole to pole passing through the like . Such lines are also called meridians. Un¬ the poles the equator which is centrally placed between begin the , any meridian could have been taken to decided in numbering of longitude. It was finally 1884, by international agreement choose as the , to zero meridian the one which passes 8 WEST 74'W I 0 * 5' (WEST W.L.S. 4- -LOSE-SUBTRACT) £ NEWYQRK I 4 hrs. ^ 56 mins. I 1 BREAKFAST I I I I 4- c LONDON 12 00 NOON LUNCH + 102* E — EGA (EAST-GAIN-ADD) ) c 3 j +5 hrs 20 mins. i 6.48 p m. DINNER Fig. 12 Longitude and time — when it is noon in London, it is 5.20 p.m. in Madras (80° E.) and 7.04 a.m. in New York (74° W.). For example: the captain of a ship in the midst of the ocean wants to find out in which longitude his ship lies. If G.M.T. is 8.00 a.m. and it is noon in the local region, it means that he is four hours ahead of Greenwich, and must be east of Greenwich. His longitude is 4 x 15° or 60°E. Standard Time and Time Zones If each town were to keep the time of its own meridian, there would be much difference in local time between one town and the other. 10 a.m. in Georgetown, Penang would be 10.10 in Kota Bharu (a difference of 2i° in longitude). In larger countries such as Canada, U.S.A., China, India and U.S.S.R. the confusion arising from the differences alone would drive the people mad. Travellers going from one end of the country to the other would have to keep changing their watches if they wanted to keep their appoint¬ ments. This is impracticable and very inconvenient. To avoid all these difficulties, a system of standard time is observed by all countries. Most countries adopt their standard time from the central meridian of their countries. The Indian Government has accep¬ ted the meridian of 82-5° east for the standard time which is 5hrs. 30 mins, ahead of Greenwich Mean Time. The whole world has in fact been divided into 24 Standard Time Zones, each of which differs from the next by 15° in longitude or one hour in time. Most countries adhere to this division but due to the peculiar shapes and locations of some countries, reasonable deviations from the Standard Time Zones cannot be avoided (Fig. 13). Larger countries like U.S.A., Canada and U.S.S.R. which have a great east-west stretch have to adopt several time zones for practical purposes. U.S.S.R. the largest country, which extends through almost 165° of longitude is divided into eleven time zones. When it is 10.00 p.m. on a Monday night in Leningrad, it will be almost 7.00 a.m. the following Tuesday morning in Vladivostock. Travellers along the Trans-Siberian Railway have to adjust their watches almost a dozen times before they reach their destination. Both Canada and U.S.A. have five time zones — the Atlantic, Eastern, Central, Mountain and Pacific Time Zones. The difference between the local time of the Atlantic and Pacific coasts is nearly five hours (Fig. 13). Fig. 13 The five time zones of North America 000 am: 7.00 am ! 8.00 am Ilk 9 https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comThe International Date Line A traveller going eastwards gains time Irom Green¬ wich until he reaches the meridian 180°E. when ht will be 12 hours ahead of G.M.T. Similar]} in going westwards, he loses 12 hours when he reaches 180°W. There is thus a total difference of 24 hours or a whole day between the two sides of the 180 meridian. This is the International Date Line where the date changes by exactly one day when it is crossed. A traveller crossing the date line from east to nest loses a day (because of the loss in time he has made); and while crossing the dateline from nest to east he gains a day (because of the gain in time he encoun¬ tered). Thus when it is midnight. Friday on the Asiatic side, by crossing the line eastwards, he gains a day; it will be midnight Thursday on the American side, i.e. he experiences the same calendar date twice! When Magellan' s ship eventually arrived home in Spain in 1522 after circumnavigating the world from the Atlantic Ocean to the Pacific Ocean and westwards across the International Date Line, the crew' knew nothing about adding a day for the one Strait, Fiji. Tonga and other islands to prevent confusion of day and date in some of the island groups that are cut through by the meridian. Some of them keep Asiatic or New Zealand standard time, others follow- the American date and time. The International Date Line is shown in Fig. 14. QUESTIONS AND EXERCISES 1 . With the aid of annotated diagrams, attempt to prove that the earth is spherical. Give as many reasons as you can. 2. Explain with the aid of fairly accurate dia¬ grams, how the tilt of the earth’ s axis on its orbital plane around the sun causes: (a) the seasons (b) the variations in the length of day and night (c) the altitude of the midday sun to change at different times of the year. ASIA WORTH AMERICA l PACIFIC |j OCEAN ^ UO NIGHT |* mo MIGHT FROAV jo THURSDAY oij 180'E Fig. 14 The International Date Line they had missed. They thought they had arrived on the 5th of September. They were shocked to be told that the date was 6th September. A modern aircraft leaving Wellington at 5.00 p.m. on Friday reaches Hawaii 4,100 miles away at 2.00 p.m. the same Friday. The same aircraft on its return jour¬ ney from Hawaii leaves at 6.00 p.m. on Friday but arrives at Wellington at 11.00 a.m. on Sunday. Can you explain this? The International Date Line in the mid-Pacific curves from the normal 180° meridian at the Bering 3. Explain the differences between any three of the following: (a) perihelion and aphelion (b) parallels of latitude and meridians of longitude (c) the earth’ s rotation and the earth’ s re¬ volution (d) solstice and equinox (e) Standard Time and Greenwich Mean Time 4. Explain any three of the following terms connected with the earth and its planetary relations: i. galaxy ii. Pime Meridian iii. elliptical orbit iv. International Date Line 5. Either: Give an explanatory account of the following. (a) Daylight increases as we go polewards in summer in the northern hemisphere. (b) The period of twilight in Britain is longer than in Malaysia. (c) A ship crossing the International Date Line at midnight on Wednesday east¬ wards finds that it is midnight, Tuesday, on the American side. 10 Or Work out the following. i. What is the approximate distance in a straight line between Cairo (lat. 30°0 N., long. 31°5’E.) and Durban (lat. 29°57’ S., long. 30°59’ E.)? ii. When it is 2.00 p.m. in Greenwich, what is the local time of (a) Sydney (long. 151°E. ) (b) Chicago, (long. 87°30 ’W.) 1 (c) Bombay (long. 73°E.) iii. The captain of a ship observed that it was local noon. He turned on the radio and listened to the 7.00 a.m. B.B.C. news. What was his longitude? SELECTED QUESTIONS FROM CAMBRIDGE OVERSEAS SCHOOL CERTIFICATE PAPERS 1 . (a) Explain the meaning of the terms ‘Equinox’ and ‘Solstice’. (b) With the aid of diagrams,show how they are related to the movements of the earth.(1967) 2. Answer the following: (a) Describe any three experiments or observations which support the belief that the earth is roughly a sphere. (b) Explain why mean temperatures for London are lowest in winter. (c) Explain why the local clock time in the Samoa Islands (171°W.) was noon on 1st November when in the Fiji Islands (178°E.), it was 11.00 a.m. on 2nd November. (1966) 3. Explain the following: (a) Polar air routes follow great circles. (b) When it is noon at Cairo (30°E.), the local time in New York (75°W.) is 5.00 a.m. (c) On 21st March at noon, it was observed that the shadow cast by a wall 4 ft. 8 ins. high pointed north¬ ward and was 7 in. long. The observer was able to calculate his latitude to be about 7°N.(1965) 4. Select two of (a), (b), (c) and draw diagrams to illustrate your answers: (a) i. Calculate the longitude of the position of a ship whose navigation officer observes that Greenwich Mean Time is 14.16 hours when the local time is noon, ii. Explain the geographical facts which enable you to make the calculation. (b) Explain fully why 25th December in New Zealand may be one of the hottest days of the year. (c) Why must a traveller, when crossing North America from New York to the west coast, alter his watch at special places. (1964) 5. With the aid of annotated diagrams, explain the following: (a) The apparent daily movement of the sun and its changes during the year as observed i. at the Equator. ii. at a place 50°N. (b) The relationship between latitude and the angle of elevation of the noonday sun. (1963) 6. Explain the effect of: (a) Latitude on temperature. (b) Latitude on the length of day and night. (c) Either Altitude on temperature. Or: Longitude on time. (1961) 1 1 https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.comChapter 2 The Earth' s Crust The Structure of the Earth In order to understand the geography of the external landforms of the earth, it is essential that we have some idea of what lies within the earth' s crust. It is not possible to know exactly how the earth was formed about 4.500 million years ago. but from the evidence of volcanic eruptions, earthquake waves, deep-mine operations and crustal borings the follow ¬ ing facts are quite clear. atmosphere O R C Mantle earth s crust (lithosphere) \ oceans (hydrosphere) Fig. 15 A section showing the structure and composition of the earth The earth is made up of several concentric layers (Fig. 15). The outer layer is the earth' s crust — the lithosphere— which comprises two distinct parts. The upper part consists of granitic rocks and forms the continents. Its main mineral constituents are s/lica and a/umina so it is collectively referred to as the sial. It has an average density of 2.7. The lower part is a continuous zone of denser basaltic rocks forming the ocean floors, comprising mainly silica. iron and Magnesium. It is therefore called sima and has an average density of 3.0. The sial and the sima together form the earth’s crust which varies in thickness from only 3^ 1 miles beneath the oceans to as much as 30 miles under some parts of the con ¬ tinents. Since the sial is lighter than the sima, the continents can be said to be ‘floating’ on a sea of denser sima. This is illustrated in Fig. 16. Immediately beneath the crust or lithosphere is the mantle (or mesosphere ) about 1,800 miles thick, composed mainly of very dense rocks rich in olivine. The interior layer is the core, (or harysphere ) 2,160 miles in radius, and is made up mainly of iron ( Fe ) with some nickel and is called nife. The temperature SIALeternity 2 7 UPPER MANTLE Fig. 16 A section showing how the continent (SIAL) floats on the denser SIMA here is estimated to be as high as 3,500°F„and the core is subject to extremely high pressure. Under such conditions, the core could be expected to be in a liquid state. But recent studies through earthquake w'aves have suggested that the innermost part of the core is probably a crystalline or solid mass. Parts of the earth’s crust are immersed by oceans and seas. These form the hydrosphere. Extending skywards for over fifteen miles, the earth is enveloped by a mass of gases which make up the atmosphere. The Classification of Rocks The earth’s crust is made up of various types of rocks, differing from one another in texture, structure, colour, permeability, mode of occurrence and degree of resistance to denudation. A knowledge of these rocks is of paramount importance to geologists, who study the composition and physical history of the earth, but the geographer, too, needs a basic knowledge of the most common rocks and their relationship with landforms. Rocks also form the basis for soil, and determine to some extent the type of natural vegetation and land use, so w'e must have a fair acquaintance w'ith the rocks around us. Generally speaking, all rocks may be classified into three major groups — igneous, sedimentary and metamorphic, according to their origin and ap¬ pearance. Igneous Rocks Igneous rocks are formed by the cooling and solidi¬ fication of molten rock (magma) from beneath the earth’s crust. They are normally crystalline in structure. They do not occur in strata (layers) nor do they contain fossils. Igneous rocks may be sub-divided on the basis of mineral composition. When they contain a high proportion of silica they 12 are said to be acid. Acid igneous rocks, such as granite, are less dense and are lighter in colour than basic rocks. T hese contain a greater proportion of basic oxides, e.g. of iron, aluminium or magnesium, and are thus denser and darker in colour. In terms of origin there are two main classes of igneous rocks. 1. Plutonic rocks. These are igneous rocks, formed at some depth in the earth s crust. They have cooled and solidified slowly so that large, easily-recognized crystals have been able to form. These intrusive rocks, such as granite, diorite and gabbro, are exposed at the surface by the processes of denudation and erosion. 2. Volcanic rocks. These are molten rocks poured out of volcanoes as lavas. They solidify rapidly on the earth' s surface and the crystals are small. Basalt is a common volcanic or extrusive rock and forms lava flow's, lava sheets and lava plateaux, e.g. those of Antrim in Northern Ireland, the Deccan Plateau in India and the Columbia-Snake Plateau in U.S.A. Some kinds of basalt solidify in a verypeculiar manner to form long polygonal columns. A well-known example is the columnar basalt of the Giant’s Causeway in Antrim. Some of the molten lava may push its way to the surface through clefts and passages, solidifying as vertical dykes or hori¬ zontal sills. Their origin and occurrence w'ill be discussed in greater detail in Chapter 3. Most igneous rocks are extremely hard and resistant. For this reason, they are quarried for road-making and polished as monuments and grave¬ stones. Sedimentary Rocks Sedimentary' rocks are formed from sediment ac¬ cumulated over long periods, usually under w'ater. They are distinguished from the other rock types in their characteristic layer formation and are termed stratified rocks. The strata may vary in thickness from a few inches to many feet. The rocks may be coarse or fine-grained, soft or hard. The materials that form sedimentary rocks may be brought by streams, glaciers, winds or even animals. They are non-crystalline and often contain fossils of animals, plants and other micro-organisms. Sedi ¬ mentary rocks are thus the most varied in their formation of all rocks. Sedimentary rocks are classified according to their age and different kinds of rocks formed during the same period are grouped together. It is more useful to know' the characteristics of the various kinds of rocks. Sedimentary rocks may be classified under three major categories in accordance with their origin and composition. 1. Mechanically formed sedimentary rocks. These rocks have been formed from the accumulation of materials derived from other rocks which have been cemented together. V ic are probably the most familiar sedimentary rocks. They are made from sand grains, often quartz fragments derived from granites. Their texture, composition and colour vary tremendously. Many types of sandstones have been quarried for building purposes or for making grindstones. A coarser type of sand¬ stone is known as grit. When larger pebbles are firmly cemented to form a rock it is called . : . rate when the pebbles are rounded, or when the fragments are angular. The finer sedimentary materials form clay, widely used for brick-making, shale or mudstone. Sand and grave! may occur in uncemented form. 2. Organically formed sedimentary rocks. These rocks are formed from the remains of living organisms such as corals or shellfish, whose fleshy parts have been decomposed, leaving behind the hard shells. The most common rocks formed in this way are of the calcareous type. They include limestones and chalk. The carbonaceous rocks are also organically formed but from vegetative matter — swamps and forests. The pressure of overlying sediments has compressed the plant remains into compact masses of carbon which eventually become peat, lignite or coal, all of which bear great economic value. 3. Chemically formed sedimentary rocks. Such rocks are precipitated chemically from solutions of one kind or another. Rock ->alt:s are derived from strata which once formed the beds of seas or lakes. Gypsum or calcium sulphate is obtained from the evaporation of salt lakes, such as the Dead Sea. which have a very high salinity. In similar ways. potash and nitrates may be formed. Metamorphic Rocks All rocks whether igneous or sedimentary may become metamorphic or changed rocks under great heat and pressure. Their original character and appearance may be greatly altered by such forces, particularly during intense earth movements. In this manner, clay may be metamorphosed into 'date, limestone into marble, sandstone into quart/ne. granite into gneiss, shale into >ohist and coal into graphite. 13 https://t.me/UPSC_PDF www.UPSCPDF.com https://t.me/UPSC_PDF Google it:- www.UPSCPDF.com