General Geography - SDC for App.pdf

Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) The universe is believed to be 15 billion year old. It consists of unimaginary huge space and stars. Stars are not uniformly scattered. They occur in clusters or galaxies. In the second century BC, a Greek Astonomer Ptolmy declared that...

Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) The universe is believed to be 15 billion year old. It consists of unimaginary huge space and stars. Stars are not uniformly scattered. They occur in clusters or galaxies. In the second century BC, a Greek Astonomer Ptolmy declared that all bodies revolve round the earth. (Geo-centric Theory) Later on Copernicus gave the theory that the Sun is the centre of the Universe. Big Bang Theory : It is explained by a Belgium astronomer, A.G.Lemeitre. According to this theory, billions of years ago, cosmic matter, i.e., the Universe was in an extremely condensed state. A big explosion broke up the super dense ball and case its fragments far out in space. A star is an extremely hot body, which emits its own light. Stars are composed of gases, mainly Hydrogen and Helium. They get collected into dense clouds at a temperature of about –173oC. They contract under their own gravitational force. This condensed mass is called a Protostar. It looks like a huge dark ball of gas. It does not emit any light. Since the density of protostar is very high, its molecules collide with each other and temperature begins to rise from –173oC to 107oC. Thermonuclear reaction starts under these conditions to fuse hydrogen into helium. Hence stars produce energy by Fusion Reaction. Final Stage of a Star’s Life (Red Giant Phase) : After some time, when the matter in its core has mainly helium, the fusion reactions stops. The pressure inside the core drops and the star begins to contract again under its own Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) gravity. However, in its outer shell, hydrogen continues to fuse and liberate energy. The shell, therefore, begins to expand, increasing its surface area and reducing the intensity of radiant energy. At this stage, the star enters Red-Giant Phase. It begins to change colour and appear red. White dwarf star : Once a star reaches the red-giant phase, its future depends on its initial mass. A star with a mass similar to sun would lose its expanding shell. The core left behind would gradually condense into an extremely dense ball of matter. The resulting high temperature in its interior then begins to convert helium into carbon. The energy liberated by fusion of helium would make this small core glow as white dwarf star as long as the helium lasts. Supernova Star : If the star is much more massive than the sun, the core of helium formed during the red giant phase would continue to contract, building up higher and higher temperatures. As this contraction continues the energy liberated causes the outer envelope to explode with a brilliant flash. The explosion of the envelope would be so great that it could release in one second, the same amount of energy that the sun radiates in about a hundred years. Such an exploding star is called a Supernova. Neutron Star : After the supernova explosion, the outer shell of the red giant star explodes and only the helium core survives. The core continues to contract under the tremendous force of gravitation and ultimately it forms an extremely dense lump of matter, which is called neutron star. Pulsar : A spinning neutron star emits radio waves and is called a pulsar. On a clear night, one can see 2000-3000 stars with naked eye. With telescope one can see around 100,000 stars. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) The colour of the stars depend on the temperature of the star. Red stars are cooler than white stars are cooler than blue stars. Yellow stars are comparatively hot. The North Star indicates the North direction. It is also known as Pole Star. It always remains in the same position in the sky. A Galaxy is a giant clusters of stars. There are three types of galaxies :- Elliptical shaped galaxies : consists of older stars. They account for about 50% of the galaxies in the universe. Spiral shaped galaxies : consists of bright and young stars. Milky Way and about 75% of the galaxies are spiral shaped. Irregular shaped galaxies : are of any shape. About 5% of the galaxies are irregular shaped. The galaxy of which our solar system is a part is known as Milky Way. It is a spiral shaped galaxy. The nearest galaxy outside Milky Way is Magelton. Constellation : A constellation is a closed group of stars resembling some human or animal shape. Great Bear is the name given to a constellation of seven stars. Sun is a fixed type of star. It is the centre of the solar system. It is made up of extremely hot gases. The star closest to our solar system is Alpha Century or Proxima Century. Twinkling of Stars : The light from star travels through different moving layers in the space with different densities and temperatures. This results in refraction of light due to which stars appear to twinkle. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Black Hole : A black hole is an celestial body with such a strong gravitational field that even light cannot escape from its surface. They cannot be seen by an optical telescope but can be detected only with the help of a radio telescope. The Sun & Solar System: Sun is believed to be 5 billion years old. It is a medium type of star. It has a surface temperature of 6000oC. The temperature at the core of the Sun is 15,00,000oC. This heat is generated by controlled thermonuclear reactions (viz., Nuclear Fusion Reaction) in which Hydrogen gas is converted into Helium gas The glowing surface of sun is called Photosphere. Above the Photosphere is the Chromosphere (reddish in colour). The outermost portion is called Corona which is visible during eclipses. The visible while light of the sun is made up of seven colours : Violet, Indigo, Blue, Green, Yellow, Orange and Red (VIBGYOR). In the Sun’s atmosphere hydrogen gas accounts for 70%, helium 28% and other elements like lithium, uranium etc. 2%. The Sun light takes 8.3 minutes to reach earth. Sun Spots : They were discovered by Galileo. They appear dark because they have lower temperature of 4500oC. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) The solar system consists of Sun, 8 Planets, Satellites, Meteoroids and Asteroids. Mercury - Closet to sun, smallest planet, No satellite, weak magnetic field, fastest moving, completes one revolution in 88 days. Venus - is closest to the earth, also known as sister planet of the earth because of the similarity in physical fabric of the planet. It is the brightest, hottest planet known as morning star or evening star. It rotates in a clock wise direction. That is from east to west which is contrary to the motion of most other planets. Venus is names after the Roman Goddess of beauty. Venus has an atmosphere in which carbon dioxide gas is found in plenty. This CO2 gas causes the green house effect & accumulates heats on Venus. Therefore Venus is the hottest planet. Venus increases and decreases like Moon in size. Mars – also known as planet with red spots. Known as world of valleys and volcanoes. It has two satellites Phobos (fear) and Deimos (terror). It has polar ice caps like earth. Its axis is tilted. Jupiter – is the largest planet in the solar system. It is 11 times larger than the earth. It has 16 satellites. Ganymede, one of its satellite is the largest satellite in our solar system. Recently, shoe-maker levy- 9 comet collided with it. Saturn – is the 2nd largest planet known for its cosmos rings, magnetic fields, 22 satellites which is the maximum no of satellite any planet has. It is the slowest moving planet & completes one revolution in 30 years. Discovered by Gallileo. Its biggest satellite is known as Titan. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Uranus - is not visibel to naked eyes and was the first planet to be discovered telescopically by William Harshels in 1781. Like Venus it also rotates clock wise and has 15 satellites. Neptune – It was discovered by J.G. Galle in 1846. It completes one rotation in 165 years The four inner most planet in the Solar system namely Mercury, Venus, Earth & mars are known as terrestrial planets. Because they have a compact rocky surface like the earth. Four other planets name Jupiter, Saturn, Uranus & Neptune are known as Jovian Planets as they have similarity with Jupiter. Jupiter, Saturn and Uranus have rings around them. These rings are belts of small debris. Asteroids are numerous tiny bodies which move around the Sun between the orbits of Mars and Jupiter. The largest asteroid is Ceres. Meteoroids are small pieces of rocks which revolve around the sun. Sometimes, these meteoroids come near the earth and enter earth’s atmosphere. During this process due to friction of air they get heated up and burn. It causes a flash of light. Hence, they are also called Shooting Stars. Sometimes, a meteor without being completely burn falls on the earth and creates a hollow. Such meteors are called Meteorites. A Comet is an icy small Solar System body that, begins to evolve gasses when passing close to the Sun. This produces a visible atmosphere or coma, and Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) sometimes also a tail. Comets usually have highly elliptical or parabolic orbits. Elliptical comets appear periodically which parabolic may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition. Hallos : Hellos are beautiful rings of colored light around sun & moon. They are caused by the reflection of light by ice crystals in the atmosphere. The Earth The Earth is the 3rd planet placed between Venus & Mars. The shape of the earth is Oblate Spheroid, i.e., it bulges out at the equator and it is flattened at the poles. The reason for flattening the pole is that the rotation of earth develops outward a centrifugal force which is maximum at the equator. The equatorial diameter – 12756 kms. The Polar diameter - 12714 kms. Geoid is the theoretical shape of the earth ignoring its surface irregularities. Earth rotates from West to East in anti clock wise direction. It completes one rotation in 24 hrs w.r.t. sun. This time period is known as SOLAR DAY. Earth completes one rotation w.r.t. any fixed star in 23 hrs 56 mins 4 sec. This time period is known as SIDERIAL DAY. Simultaneous with the rotation, the earth also moves round the sun known as Revolution. Earth completes one revolution in 365 days 5 hrs 48 mins and 45 secs. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Earth revolves around the sun in a fixed path which is elliptical in shape and is known as Orbit. Aphelion : The longest distance between the Sun and the Earth (or any other planet). The earth reaches its aphelion on 5th of June. The longest distance between the Sun and the Earth is 152 million Kms. Perihelion : The shortest distance between the Sun and the Earth, i.e. 147 million Km. The earth reaches its perihelion on 4th January. Apogee and Perigee : The position in the orbit of the moon or any planet farthest from the earth is called Apogee and the point nearest to the earth is called Perigee. The earth has only one satellite, viz., Moon. Its diameter is only one-quarter of that of Earth. It is 3,84,400 km away from the earth. It revolves around the earth in about 27 days. Its rotation period is also exactly the same. As a result, only one side of the moon is visible to us. Days and Nights are formed as a result of the rotation of the Earth. Another important effect of rotation is that winds and currents change their direction. They turn towards right in Northern Hemisphere and towards Left in Southern hemisphere. This is known as Ferrel’s Law. Change of seasons occur because of : (i) Revolution of the Earth. (ii) Inclination : The two hemisphere experiences summer which they are in the front of sun and winter when they are away from the sun. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Summers are hotter because summer days are longer than night. During day time earth absorbs heat from the sun and during night it radiates heat. Since days are longer the earth absorbs more heat and is able to radiate less heat. Heat accumulates and makes summer hotter. The axis of the earth is an imaginary line passing through the centre of the earth. The axis of the earth always points in the one direction in the space. Earth spins round its axis which remain inclined at an angle of 66 ½ o to the plane of its orbit. The ends of the axis are called poles one is North Pole and other South Pole. Tropics are the turning points from where the sun starts reverse journey. 231/2o North of equator is known as Tropic of Cancer and 231/2o south is known as Tropic of Capricorn. SOLSTICE is a date when sun shines over any tropic. Sun shines vertically over Tropic of Capricorn on 22nd December – it lies in Southern hemisphere, as a result there is summer solstice in the southern hemisphere and winter solstice in Northern Hemisphere. Sun shines vertically over Tropic of Cancer on 21st June – it lies in Northern hemisphere, as a result there is summer solstice in the northern hemisphere and winter solstice in Southern Hemisphere. Equinox is the position when sun rays falls vertically over equator making the duration of days and nights equal throughout the globe. This happens twice Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) a year, i.e. on 21st & 22nd March, which is known as Spring Equinox and 22nd and 23rd September called Autumn Equinox. Equator is imaginary line passing round the earth midway between north and south pole. It thus divide the earth in two equal halves i.e., Northern hemisphere and southern hemisphere. Latitude is the angular distance from equator. They are the parallel liens to the equator. The latitude of equator and as we move towards poles the latitude rises. At poles it is maximum i.e. 90o Horse Latitude : 350 N and S of equator there is always a high pressure area. Hence they are known as Horse Latitude. Arctic Circle is the circle drawn at 23 ½o North Pole. Antarctic Circle is the circle drawn at 23 ½ o South Pole. Torrid Zone : The area between 231/2o North and South of equator i.e. between the tropic of Cancer and tropic of Capricorn. This is the hottest zone since the rays of sun are nearly perpendicular than in any other zone. Frigid zone : The area between the North pole and Arctic circle is known as North frigid zone and between South pole and Antarctic Circle is known as South Frigid Zone. Temperate Zone : lies between 661/2o Tropic of Cancer and Arctic circle is known as North Temperate Zone Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Meridians are imaginary lines drawn on the global map connecting the two poles. There are 360 meridians in all. For the sake of convenience the meridians passing through Greenwich is known as Prime Meridian. The distance between two successive meridian is 111 Kms and there is a time difference of 4 minutes. Longitudes are equidistant lines drawn east to west of Greenwich meridian. They denote angular distances of a place east or west of the Prime meridian. The local time of the place is 12.00 noon when sun shines vertically overhead. It varies from GMT @ of 4 mins for 1o change in longitude. Greenwich Mean time (GMT/World Time) is U.K’s standard time. It is based on the local time of the Prime Meridian. Standard time is the local time of a place used through out the country. Indian Standard Time is local time of the place near Allahabad (Mirzapur) o situated at 821/2 East longitude. International date line : 180o meridian is called as International date line. When ships cross this line while going towards east they add a day and while going towards west they omit one day i.e. count the same date again. Mid Night Sun : The places within the Arctic circle and Antarctic circle remain in light for some period during their respective summer. There is a day of 24 hrs. This phenomenon is known as Mid-night Sun. It can be seen at places on North and South pole. The places from where this phenomenon can be seen include Norway, North Russia, Greenland etc. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) 70% of the total surface area of the earth is covered with water called as Hydrosphere. 29% of the area is land portion and is known as Lithosphere. The average thickness of Lithosphere is 60 Km. The crustal layers comprises of rocks, rich in Silicon and Aluminium – SIAL Below SIAL lies MENTAL upto a depth of 2900 kms it consists of SIMA i.e. Silicon and Magnesium. The core of the earth consist of metal in liquid form. It has a radius of 3400 Km. As Nickle and Iron are dominant in the core called NIFE. NIFE accounts for the magnetism of the earth. The most abundant elements in the crust are Oxygen 49.8%, Silicon 26.03%, Iron 4.12 %, Calcium & Sodium in smaller quantities. Atmosphere is the gaseous envelop of the Earth covering 300 miles. It consists of Nitrogen (78%), Oxygen (21%), Argon, Carbon Dioxide, Helium, Methane, Hydrogen, Ozone, etc. The atmosphere is essential for life on the Earth. Oxygen and CO2 are necessary for animal and plant life. The Ozone layer in the stratosphere protects life by absorbing most the sun’s harmful radiations or ultraviolet rays. The different layers of atmosphere are :- (a) Troposphere : is the nearest to the earth and extends upto a distance of 11 Kms (8 miles). It is the densest of all layers and Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) contains water vapours, moisture and dust. All the climatic changes taken place in Troposphere. The upper most part of troposphere is called Tropopause. (b) Stratosphere : is the region of uniform temperature. It extends from 11 Kms to 30 Kms (upto 26 miles). It is free from water vapours, clouds and dust. Because of the relatively calm conditions, jet aircrafts fly only in this zone. (c) Mesophere : is a very cold region above the ozone layer of stratosphere. (d) Ionosphere : extends from 50 Kms to 500 Kms. The region contains ionised or electrically charged air and reflects radio waves facilitating wireless communication and shortwave transmission. The ionized air also protects us from the falling meteorites most of which are made to burn in this region. (e) Thermosphere : contains the middle layer of ionosphere and has a temperature of 1000C (2120 F). (f) Exosphere : is the uppermost region of the atmosphere. Here the density of air is very low. The ozone layer is found in the atmosphere between 20-50 Km from the Earth's surface. The ozone layer is a region of concentration of the allotrope of an oxygen molecule known as ozone (O), which is produced by the action of solar radiation on ordinary oxygen atoms. It filters sunlight and prevents the harmful ultraviolet radiation from reaching the Earth's surface by absorbing most of the ultraviolet radiation. Presence of the ozone layer is an Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) essential factor in the life environment. There are certain household and industrial chemicals, having widespread application in refrigeration, air conditioning, fire extinguishing and dry cleaning, etc. that are known to deplete this life-saving layer. These chemicals are called Ozone Depleting Substances and include primarily the Chlorofluorocarbons (CFCs), Carbon Tetrachloride (CCI.) and Hydro Chlorofluorocarbons (HCFCs). With less ozone in the atmosphere, more ultraviolet radiation reaches the Earth, leading to a higher incidence of skin cancer, cataracts, destruction of certain forms of aquatic life, reduction in crop yields and damage to the immune system. The lines connecting places of equal atmospheric pressure are called isobars. The instrument used to measure atmospheric pressure is called Barometer. Doldrums or Equatorial Calms : is the region of low pressure are 50N & S of equator. Since the sun rays fall vertically over this region most of the time, the area is comparatively hot. The excess heat causes heavy evaporation, upward movement of air, formation of dense clouds and heavy rains throughout the year. Planetary Winds : These are permanent winds which blow throughout the year from one latitude to the other in response to the latitudinal differences in air pressure. Trade Winds : Near 300 N & S of equator, there is always a high pressure area. From this high pressure belts, winds blow throughout the year towards Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) equator. They are regular and bring rainfall towards the eastern side of the continents. These winds have been taken advantage of by sailors in early days who gave them the name. (Easterlies) Anti-Trade Winds : Winds which blow from 300 N and S of equator towards poles are called Anti-Trade winds or westerlies. Since there is always a high pressure at 300 N & S of equator, this latitude is known as Horse Latitude. Polar winds : The winds which blow from high pressure area around the poles towards the temperate regions are known as polar winds. These are extremely cold winds. They rise from north-west in the northern hemisphere and south-east in the southern hemisphere. Gale is the name given to strong winds having a speed between 56 Km/Hr and 72 Km/Hr. Storm refers to a strong winds whose speed varies between 72 Km/Hr and 121 Km/Hr. Hurricane denotes strong winds whose speed exceeds 121 Km/Hr. Sea Breeze : During day time, landmass becomes hotter than sea water. A breeze blows from sea towards land which is known as Sea Breeze. Land Breeze : During night time, landmass become cooler than sea water. A breeze blows from land towards sea which is known as Land Breeze. Monsoon Winds : Monsoon is derived from an Arabic word mausim meaning season. These winds are seasonal winds. According to Flohn’s theory, the monsoon is a modification of the general planetary wind system. It is a south-westerly wind and is the northward extension of the equatorial lows. The tropical easterlies is embedded by equatorial westerlies and both flow northward. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Cyclone : It is a storm system of great intensity with winds circulating at a speed of 120-180 Kms per hour around the ‘eye’ or centre of the cyclone and accompanied by torrential rain. Thus, cyclone is an area of low pressure winds that rotate in anti-clockwise direction in the northern hemisphere and in a clockwise direction in the southern hemisphere. Anti-Cyclone : An area of high pressure in the atmosphere. It is shown on weather chart by a series of roughly circular isobars around the area of highest atmospheric pressure. In the northern hemisphere, the winds circulate clockwise and in the southern hemisphere, the direction is anti- clockwise. The anti-cyclone generally moves more slowly than a cyclone. Tornado : It is violent spiraling storm of the cyclonic type which is very common in the West Indies and the neighboring parts of the USA. The earth rotates round the sun and the moon (a natural satellite of the earth) moves round it. Many times the earth comes between sun and moon. Since all bodies in the solar system take light and heat from the sun. Earth causes its shadow on the moon. This is known as Lunar Eclipse. As the earth the moon and the sun are in the same plane the lunar eclipse occur only on a full moon day. Solar eclipse : When moon comes between the sun and earth, it causes its shadow on the earth known as Solar eclipse. It happens only on a new moon day. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Tide is the periodic rise and fall of sea water. The rise and fall occur alternatively twice a day. The tides are caused by the gravitational pull of the moon and the sun on earth’s surface including the sea water. Spring Tide : When sun and moon are in the same line they pull earth gravitationally in the same direction. The combined pull causes a high tide known as Spring Tide. Neap Tides : When sun and moon are at right angle the gravitational pull is exerted in a opposite direction and tide’s caused are low. There are called Neap Tides. Rift valley is a long & Narrow valley formed by sinking of a portion of the earth. A vast accumulation of ice which moves slowly till it melts and forms a river is known as Glaciers. Ice Berg is a large mass of ice which is detached from Glacier & keeps floating in the sea. Geyser is a fountain of hot water issuing from a hole which extend deep into the earth crust. It also contains minerals. COUNTOUR LINES : are lines joining places of equal heights above the sea level on a map. ISOTHERMS : are lines connecting places of equal temperature. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) ISOHELS : are lines connecting places of equal sunshine. ISOLATES : are lines joining places of equal rainfall. ISOHALINES : are lines joining places of equal sea salinity. ISOBATHS : line of equal sea depth. Durand Lind : boundary line between India and Afghanistan. McMohan Line : boundary line between India and China. Red Cliff Line : boundary line between India and Pakistan. Snow Line : Is the line beyond which snow never melt. It varies according to altitude. Rocks Igneous rocks – are formed by the cooling of Molten lava or magma. They are also known as primary rocks almost 95% of the earth crust is made up of Igneous rocks. E.g. Granite, Basalt, Quartz. Sedimentary rocks – are formed by material which has accumulated as a result of various process such as deposited by river, wind etc. Eg. Chalk & Lime stone. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Metamorphic rocks – are formed from Igneous rocks or sedimentary rock by heat pressure or action of water. Eg. Limestone is converted in marble, sandstone is converted into quartzite etc. Weathering : is breaking up or disintegration of rocks in situ. Chief agents are temperature, air pressure, rain etc. The Continents The land surface of the earth is made up of immense land masses, divided into seven continents and a great number of islands. Together, they cover about 29% of the earth’s surface. Origin of Continents : It is believed that originally there was only one land mass called Pangaea. This large land mass split into a northern mass called Ankaraland and a southern one called Gondwanaland. From these two land masses, the continents gradually drifted to where they are not located and the process is still continuing. The largest continents is Asia and the smallest is Australia. The Island continents are Antarctica and Australia. The Ice-covered continent is Antarctica. The most thickly populated continents is Asia having approximately 59% of the world population followed by Africa (13%). The continent having the smallest population is Australia with 3.2% population. Mountains : Mountains are land masses with peaks smaller than their base and of a height above 300 m or 1000 ft. Similar elevations below 300 m or 1000 ft. is called a hill. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) Largest mountain range is Himalayan – Karakoram range in Asia. The Highest mountain peak is Mt. Everest. Some other important ranges are : Andes – South Africa; Alps – Europe; and Rockies – North America. Young or new mountains have come into being after the continental drift started with the break up of the large land mass of Pangaea. The Himalayas, the Andes, the Rockies and the Alps are examples of new or young mountains. Old mountains are those which are formed in the pre-drift era long before the continental masses came together to form Pangaea. The Appalachians (America) and the Aravallis (India) are examples of old mountains. Types of Mountains : There are broadly four types of mountains which are differentiated on the mode of their origin or formation, viz., (i) Fold Mountains : The mountains formed by the crumbling or folding of rocks, resulting in huge wrinkles or fold upon the earth’s surface as well as the ocean floors are called fold mountains. These are formed as a result of a series of earthquakes. Most of the mountain systems like Himalayas, Alps, Andes, Rockies, etc. are examples of Fold Mountains. (ii) Block Mountains : A mountain mass formed by the lifting up of land between faults (cracks in the rock strata) or by the sinking of land Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today  Happy Institute C-6/36, Keshav Puram, Delhi-35 (8586020110) outside the faults are called block mountains. They are formed when a mass of elevated land under strain, cracks, leaving a higher elevation standing between two areas of lower elevation. The Vosges in France and the Black Forest mountains in western Germany come under this class of mountains. (iii) Volcanic Mountains : A volcano is a mountain formed of material that has erupted from inside the earth through an opening in the earth’s crust. Super heated molten rock matter called lava is ejected forming a hill, conical in shape with a funnel shaped hollow at its top called a crater. For example, Mt. Fujiyama in Japan and Mt. Vesuvius in Italy. (iv) Residual Mountains : Mountains that are deeply dissected and reduced by weathering and river action are called residual mountain. Earthquakes An earthquake is the vibration of Earth produced by the rapid release of energy. This energy radiates in all directions from the source, focus, in the form of waves. Just as the impact of the stone sets water waves in motion, an earthquake generates seismic waves that radiate outwards from the earth's interior. The intensity of an earthquake and the destruction it causes are greater over softer soil regions, for example on alluvial soils, than on more rocky areas. Sometimes, the tremendous energy released by atomic explosions or by volcanic eruptions can also produce earthquakes, but these events are usually too weak and infrequent. Delhi’s No.1 Result Oriented Coaching Institute For SSC Graduate/HS Level, Bank PO/Clerks, Other Competitive & Entrance Exams, Shorthand & Typing –35 years of Teaching Experience, Hundreds of Selections, Practice through Online Mock Tests, Metro Connectivity – Ltd. Seats … Join Today