Geography UPSC Notes Complete

Origin of Universe

• Before Big Bang the present universe was confined into an atom size spec/ ball.
• This was stage of singularity. Singularity means the stage when there is no space no time no matter exists.
• During this time there was infinite pressure, temperature, and density.
• The four fundamental forces which govern the entire universe where also combined together. It includes:-
  1. Gravity:- Gravity pulls four objects with mass towards each other. Due to this force planets are orbiting stars.
  2. EM-force:- It acts between electrically charged particles. It is responsible for lightning, electricity, etc.
  3. Strong Nuclear force:- It binds quarks together to form protons and neutrons. Without this force atoms could not exist.
  4. Weak Nuclear force:- It plays a key role in nuclear reaction. It has been converting one type of particle into another. It causes certain types of radioactive decay.
• About 13.8 billion years ago this atom-sized spec started expanding, this event is called the Big Bang.
• The expansion of this universe was initially relatively slow. This time is called the Planck Era ( 0 to 10^-43 second).
• After Planck's era a universe expands anonymously in a tiny fraction of seconds, that is, about 10^-36 to 10^-32 seconds. This phase is called the phase of cosmic inflation.
• Thereafter a universe keeps on expanding even at the present but with relatively slower speed.
• Due to continuous expansion, universe density, temperature, and pressure decrease, in other words, cooling of the universe started.
• After the Big Bang, the fundamental forces also got separated. The force of gravity was the first one to operate.
• Due to cooling of the universe, electrons, protons, and neutrons were formed, which later on combine to form the first atom. The first element was Helium, followed by Hydrogen.
• The large clouds of Hydrogen, Helium led to the formation of galaxies and stars, and this way the universe came into being.

Main Evidences

1. Redshift theory:- It was given by Edwin Hubble in 1929. According to this theory, when a source of light moves away from an observer, its light waves get stretched and the wavelength becomes longer and shifts towards the end of the visible spectrum. Hubble observed that the stars of the distant galaxies are moving away from us, thus the universe is expanding.
2. Cosmic Microwave Background Radiation:- was given by Wilson and Penzias in 1965. They found that Cosmic Microwave Background Radiation is left over thermal radiation from the early universe. Because of this radiation, the temperature of the universe is 2.7 K, which is nearly the same temperature in all directions. It means the universe had an origin.
3. Pressure of light Elements in the Universe:- It is one of the strongest evidence for the Big Bang. According to this, the universe is filled with hydrogen (75% by mass) and helium (25% by mass).

Limitations

1. Can not explain singularity.
2. Can not explain what happens before the Big Bang.
3. Was there only the Big Bang or multiple Big Bangs, Only universe or multiverse?

Steady State Theory of Origin of Universe

• Universe has always existed and will always i.e. it is permanent.
• The universe is expanding but its overall appearance remains same over time.
• The galaxies move apart, new matter is continuously created in empty space to maintain a constant average density.

Difference between Big Bang Theory and Steady State Theory

Galaxies

• Galaxies are huge groups of stars or vast collection of stars, planets, gas, dust, etc. held together by the gravity. There are 3 types of galaxies:
  1. Spiral Shape Galaxy:- Such galaxies have arms e.g. Milky way galaxy have 6 arms. Our solar system lies in Orion path. Similarly our nearest galaxy Andromeda.

     

  2. Elliptical Shape:- e.g. Cygnus A
  3. Irregular shape Galaxies:- Such galaxies do not have any particular shape e.g. Magellanic Clouds Large and Small. These two galaxies are satellite galaxy of milky way.
• There is a presence of high gravity in the centre of galaxy which are mostly black holes e.g. name of the black hole present in the centre of galaxy, milky way is Sagittarius A.
• Galaxies have their peripheral which are called cradles or birth place of star from where new stars are formed.
• Quasar is one the brightest object in universe. It is extremely bright centre powered by super massive black hole.
• Our Milky Way galaxy is a part of local group which contains 52 to 54 galaxies. Local group is part of Virgo Supercluster.
• Virgo Supercluster is part of Laniakea Supercluster. Eventually part of Pisces-Cetus Supercluster Complex.

Stars

Stars are those celestial bodies which have their own light which comes out due to nuclear fusion which take place at the core of the star. The life cycle of star is as follows:-

Nebula

Proto Star

T Tauri Stage

Main Sequence Star

Red Giant and Super Red Giant Star

1. Red Giant:- Small and medium size stars, which loose their fuel gradually, which has mass up to maximum 8 solar masses enter into the stage of red giant. In this star become much larger then the main sequence star.
2. Super Red Giant:- Large size of stars which consume their fuel faster than small stars, which have mass more than 8 times of solar mass enter into the stage of super red giant. In which size of star become very large due to nuclear fusion of heavier elements like helium, carbon, oxygen, etc in successive stage.

Planetary Nebula Stage

White Dwarf

Super Nova Explosion Stage

Neutron Star

Pulsor Star

Black Hole

Solar System

Sun

Sun Spots

Solar winds

Solar Flares

Solar Prominence

Planets

• Objects which revolved around sun
• Should have sufficient gravity to give spherical shape
• It must have clear neighbourhood (of orbit)

Mercury

• Mercury is the first planet from the sun.
• It is about 55% the mass of the earth.
• It has about 38% of earth's gravity.
• It has prograde rotation i.e. west to east.
• It has second hottest planet of solar system.
• It has no moon.

Venus

• It is second planet form the sun.
• It is considered as earth's twin because of almost similar size and mass.
• It has retrograde rotation i.e. east to west.
• It completes its one rotation in 243 earth days i.e. the slowest rotation among the major planets.
• It completes its one revolution in 225 earth days, thus is a day is longer than the year on Venus.
• Venus is hottest planet of solar system because it has very high concentration of green house gases CO₂ i.e. about 96.5% if it rains of Venus it is mainly carbonic acid or sulphuric acid.
• The average temperature of Venus is 465^o C.
• It is brightest planet also. It is called morning and evening star.
• It is called goddess of beauty.
• It has no satellite.

Earth

• Third Planet.
• Its average density is 5.5g/cm³.
• Only planet where water is found in liquid state. It is because of its ideal temperature.
• It has ideal temperature because it is situated at a ideal distance from the sun. This ideal distance is called habitable zone or goldilock zone.
• It has one natural satellite called moon.
• Moon was formed 4.4 billion years ago where as earth was formed 4.5 billion years ago.
• Moon revolve around the earth in about 27 days and almost same it take to complete its one rotation also.
• Earth average orbital speed is about 30 km/s.
• Escape velocity form the earth is 11.2 km/s.

Mars

• It is fourth planet from the sun.
• It is called red planet because it contains red rock that is because of oxidation.
• It complete its one rotation in 24 hours and 37 minutes i.e. very close to earths rotation (Earth sideral day is 23 hours 56 minutes 4 seconds, Earth solar day is 24 hours )
• Mars has 2 moons. Deimos and Phobos.
• Earlier mars had strong magnetic field (billion of years ago) but now it does not have strong magnetic field.
• Largest volcano of solar system is Olympus Mons and this is on mars.

Jupiter

• It is fifth planet from the sun.
• It is gas giant
• It has 318 times greater mass then the earth.
• It has faint ring.
• It has 95 moons
• It has largest planet of solar system.
• It is made up of hydrogen 90%, helium 10%. It has traced amount of methane ammonia and water vapour.
• It complete one rotation in 9 hours 56 minutes. This makes it the fattest rotating planet in the solar system.
• It completes its one revolution in 11.86 years on an average 12 years. That's why Khumb Mela is celebrated after every 12 years at 4 places
  1. Haridwar, Ganga river
  2. Prayagraj , Ganga river
  3. Ujjain , Sipra river
  4. Nasik, Godavari river
• Its important moons are
  • Io - most volcanically active body in the solar system.
  • Europa
  • Ganymede - It is bigger than mercury. It is largest moon in the solar system.
  • Callisto

Saturn

• It is sixth planet from the sun.
• It is gas giant.
• It has prominent ring.
• It have 270+ moons. Major moons are:
  • Titan - It is second largest moon of solar system larger than mercury.
  • Enceloadus - It is covered with ice.
  • Rhea
  • Lapetus
  • Dione
  • Mimas
• Second largest planet in solar system made of 96% hydrogen and 3% helium.
• It complete its one rotation in 10.7 hours or about 10 hours 33 minutes.
• It complete its one revolution in 29.5 years.
• On north pole of Saturn storms are developed in hexagon shape.
• The density of Saturn is less than water

Uranus

• Seventh planet
• It is ice giant.
• It has 28 moons. Important moons are
  • Titania - Largest moon of Uranus.
  • Obreon
  • Aerial
  • Miranta Most of the moons are name after character from William Shakespeare plays.
• It colour is blue-green. The reason behind blue of Uranus is good presence of methane gas. Methane gas absorbs red light and reflects blue-green light.
• Uranus is third largest by diameter and fourth largest by mass.
• It's rotation is retrograde i.e. east to west alike Venus.
• It complete it's one rotation in 17 hours 14 minutes and revolution in 84 years.
• Uranus is titled on it axis by about 98^o.
• It has also a faint ring.

Neptune

• It is eight and farthest form the sun.
• It is ice giant.
• It has about 16 moons. Its famous moons are-
  • Proteus
  • Larissa
  • Neried
• It has faint rings.
• It has blue colour.
• It rotates west to east and completes it's one rotation in 16 hours and its complete one revolution in 165 earths year.
• Neptune experiences fattest wind blow of our solar system sometimes faster than 2000 km/h.

Dwarf Planets

• which revolve around the sun
• have spherical shape
• but do not have clear neighbourhood orbit. There are five dwarf planets.

1. Pluto - Largest one.
2. Make Make
3. Howme
4. Eris These four lie in Kuiper Belt
5. Ceres - Smallest dwarf planet. It lies in asteroid belt

Asteroid Belt

Meteors

Comet

1. Kuiper Belt i.e. located beyond Neptune. From here short period comets come
2. Oort Cloud - from here long period comets come which have time greater than 200 years. The very famous comet called Halley's comets come after 76 year last appeared in 1986. It is expected again in 2061.

Oort Cloud

Earth

• Earth like shape which is unique.
• It has spherical shape/ Spheroid but it is not perfect square because it has flattening on the pole because of maximum centripetal force and maximum centrifugal force.

Motion of Earth

1. Rotation Earth rotates on axis and complete its rotation in 24 hours called solar day or in 23 hours 56 minutes and 4 seconds called sideral day. Earth completes its rotation on its axis which is titled at 23.5 day at present. However, according to Milankovitch cycle the earth tilt axis values between 22.1^o and 24.5^o in a time span of 41000 years. There is another motion on the earths axis which occurs due to wobbling in the earth. This motion is called precision which complete one cycle in a time frame of 26 thousand years.
2. Earth Revolution Revolution is motion of earth around sun in its orbit earth completes its one orbit in 365.6 days because of orbiting motion i.e. revolution as well as tilt of earth it experiences seasonal change. Revolution and rotation both cause dynamic changes on the earth surface rotation causes day and night as well as flatting on the pole and belonging on equator. Eccentricity is about the change in the shape of Earth's orbit which goes from near circular to highly eccentric in time frame of 1 lac years. Eccentricity/ Obliquity/ Precession influenced the amount of insolation reaching on earth. In other words it affect climate change.

Longitude and Latitude

Time Zones

• 

  Many countries in the world have more than one time zone because of high latitudinal extend or east to west expansion of their geographical area. e.g. Russia have more than 10 time zones, US have more than 5 time zones. However, France has maximum number of time zones specially because of its colonial past. India has only one time zone i.e. IST (Indian standard time) is based on longitude of 82.5^o E near Mirzapur/ Parayraj Uttar Pradesh. This means that the entire country form Gujrat from in west to Arunachal Pradesh in the east uses the same clock time. However, the longitudinal distance between the western and eastern most part of India is about 30^o. That's why a debate is going on in the country on having two time zones in India.

Why India should have 2 time zone?

1. Huge difference in sunrise and sunset
   1. Dong on Arunachal Pradesh experiences sunrise during summers at 4 AM approximately
   2. Bhuj of Gujrat experience sunrise around 6 AM during summers As a result sun rises nearly two hour earlier in eastern India than the western India. Due to this people in North east India start their day much earlier besides this offices and school open after sunrise by a large margin which causes loss of or wastage of valuable day light
2. Energy Savings: Research by India's scientific agencies and studies by the government expert committee suggest that advancing time in the north east could save electricity. The national institute of advance studies i.e. NIAS, Bengaluru estimated annual savings of around 200 to 270 million units if eastern India adopts a separate time zone. By doing this less artificial light is needed in the evening.
3. Better productivity and health: People naturally function according to daylight this is called scardian rhythm. In the north east early sunrise but late office timing create a mismatch. Children often go to school long after sunrise. Workers loose their productivity because of late start in the morning. Thus, aligning clock time with sunlight can improve sleep cycle, work productivity and health outcomes.
4. Many large countries have multiple time zones e.g. Russia, US, Canada, Australia, etc.

Why India should not have two time zones?

1. Railways and Aviation safety: India operates one of the worlds largest railway networks. Historically before independence different cities of India had different time zones like Bombay time, Calcutta time, Madras time, etc. This was creating a lot of confusion. Today over 13 thousand passenger trains run daily and thousands of flights operate annually. Creation of two time zones could increase scheduling complexity and risk of error.
2. Administrative complexities: If Assam follows one time and Bihar another it would make very difficult to operate government offices, banks, courts, national examination, stock markets etc.
3. Economic Integration: India is highly integrated economically. Thus every business prefer one clock, one market opening time and one office schedule. Multiple time zones may increase coordination cost.

Alternate solution

Geomorphology

• Earth's interior
• Continental Drift theory
• Plate Tectonics theory
• Volcanic
• Earthquake
• Mountains, Plateaus, Plains
• Weathering and Erosion
• Rock and Rock cycle
• Landforms by
  • Rivers
  • Winds
  • Glaciers
  • Ground Water
  • Costal waves

Earth's Interior

1. Nebular Hypothesis: It is most accepted hypothesis today it was given Immanuel Kant in 1755. It was later developed by Laplace in 1796. It's main idea is that the solar system was formed form rotating cloud of gases and dust called Nebula. The gravity caused the centre of nebula to collapse. It formed sun at the centre and the remaining materials formed planets.
2. Planetesimal Hypothesis: It was proposed by Chamberlin in 1905.
3. Tidal Hypothesis: It was given by James Jeans and Jeffreys in 1917.
4. Binary star Hypothesis: It was given by Russell.
5. Dust Cloud Hypothesis: It was given by Gerard Kuiper. If we consider any of these hypothesis right and we know that earth was formed 4.5 billion years ago when it was hot semi molten and later on solidified then the earth surface should be smooth plane surface but it is not so. The earth surface is highly irregular and full of relief features mainly due to endogenic forces which operate form earths interior.

Study of Earth Interior

Direct Methods

1. Deep Mining:- Till date latest scientific tools and technology we have reached up to the depth of 8 to 12 km only. However, it suggest that with increasing depth temperature and density increases.
   • Study of temperature:- with increasing depth temperature increases by 1^oC/32m but this rate of increase in temperature is restricted only up to 8km beyond that temperature increases but with relatively slower rate. That's why calculation suggest that at the depth of core temperature is about 5000 to 5500^oC. Causes of such high temperature
     1. Trapped primitive heat since the formation of earth in its interior.
     2. Concentration of radioactive elements like Uranium and Thorium which decays and produces high amount of heat. The maximum concentration of radioactive elements is in the upper mantle.
     3. Conversion of gravity into heat.
   • Study of Pressure:- with increasing depth pressure increases. Pressure is force per unit area which is applied upon the lower surface by overlaying surface. This is why core bears maximum pressure followed by mantle followed by crust. To be more precise inner core maximum pressure followed by outer core, lower mantle, upper mantle, lower curst and upper crust. with increase in pressure
     • temperature increasing with increasing depth
     • melting point of the rocks also increases. with increasing depth density of rocks gradually increases this is why there melting point also high e.g. the top most layer of the earth surface is made up of silica and aluminium that has least density the middle layer is made up of silica and magnesium whereas innermost part is made up of nickel and ferrous. Earth surface rocks has average density of 2.6g/cm³ to 3g/cm³ whereas core has 10-30g/cm³ this is why average density of 5.5g/cm³

Indirect methods

1. Study of Meteors Meteors helps us in gaining direct observation. Meteors are rocks flying in space attracted by earth's gravity and hit the surface of earth as a solid mass. Meteors are the remnants of the past which reviles the process of formation of solar system as well as earth. In 99% cases these meteors are made up of iron and nickel which gives clear indication that the earth core should also be made up of iron and nickel.
2. Study of Volcanism Volcanic eruption is eruption of molten rocks from the interior with burst which clearly suggest that in the earth interior temperature, pressure and density all three increases with increasing depth

   

3. Study of Seismic waves Seismic waves are most effective method to know about interior because these are the only methods to pass through the entire interior of earth. Seismic waves are of two types:-

   

   1. Surface waves:- Surface wave originates from epicentre and do not travel thorough interior of earth. It travel only on the surface. These are of two types L waves and R waves
   2. Body waves:- Body waves originates from focus and it travel only through the interior. These are two types of:-
      1. Primary waves of P waves Primary waves carry maximum energy and have maximum velocity and shortest wavelength. It can pass through solid, liquid and gaseous medium. It refracts when medium is changed.
      2. S waves S waves carry lesser amount of energy and velocity than the P and its wavelength is also longer than P. It can only through solid medium. It also refracts when medium is changed.

         

         

Structure of Earth Interior

1. Crust Further study suggest that crust has also two layers, upper crust and lower crust. Upper crust is further divided into two parts
   1. Oceanic Crust:- It has thickness of 0-10km. It is primarily made up of basalt.
   2. Continental Crust:- Continental crust has thickness of 35-40km. It is primarily made up of granite. upper crust is separated from the lower crust by Conard discontinuity.
2. Mantle Mantle has two parts
   1. Upper Mantle:- Upper mantle is separated from lower crust by mohorobic discontinuity. It is also called aesthenosphere.
   2. Lower Mantle:- Lower mantle is separated from upper mantle by repiti discontinuity. It extends up to depth of 2900 km.
3. Core Core is divided into two parts
   1. Outer core:- It is in liquid state. It extends from 2900km to 5150km. This layer is responsible from electromagnetic shield of the earth. It is separated from lower mantle by Guttenberg discontinuity.
   2. Inner Core:- Inner core is in solid state. It extends between 5150km to 6370km.

      

Geomagnetism

Causes of Geomagnetism

• The outer core consist mainly of molten iron and nickel.
• Convection currents caused by heat escaping from the core lead to the movement of these electrically conductive fluids.
• Combine with the earth's rotation, Coriolis force, these motion generate electric currents.
• The electric current in turn produces earth's magnetic field.

• 

Impact of Geomagnetism

• Protection form solar radiation.
• Deflects charged particles from the sun, preventing harmful radiation form reaching the earth surface.
• Formation of Auroras:- Interaction between solar winds and magnetic field produces auroras near polar regions.
• Geomagnetic Storms:- Strong solar activity can disturb the magnetic field affecting satellite, ISS, communication system, GPS and power grids.
• Magnetic Navigation:- Compasses aligned with earth's magnetic field and aid navigation.

Importance of Geomagnetism

• Essential for the existence and evolution of life by shielding earth from solar and cosmic radiation.
• Helps in navigation of ships, aircrafts, mitigatory birds like Amur Falcon which flies from Magnolia, Southern Siberia, Northern China to South Africa, Zimbabwe, Namibia and Botswana via India, Nagaland where it rests for few weeks or months. Similarly, Siberian birds coming from Siberia to Bharatpur of Rajasthan.
• It provides clues about the earth's interior and core dynamics.
• It support space weather forecasting and satellite operations.

Recent Development

• Scientist continue to monitor the weaking and shifting of the magnetic field particularly the South Atlantic anomaly where magnetic intensity is usually low.
• European space agencies, swarm satellites to study changes in earth's magnetic field to improve understanding of the earth's interior core process and space weather.

Conclusion

Auroras

Causes of Auroras

• The sun continuously emit charged particles called the solar winds.
• The earth's magnetosphere channels these particles towards the polar regions.
• The particles collide with gases in the upper most atmosphere mainly between the altitude of 80-400km i.e. ionosphere.
• There is presence of oxygen and nitrogen gases which become excited due to this interaction and release energy in the form of visible light.

Colours of Auroras

1. Green Colour:- It is mainly due to the presence of oxygen between 100-300km. It is most common colour.
2. Red Colour:- It is because of oxygen between 300-400km.
3. Blue and Purple Colour:- It is because of Nitrogen.

Importance of Auroras

1. Indicator of space weather:- Auroras helps scientist to monitor solar activity and geomagnetic storm.
2. Evidence of earth-sun interaction:- Demonstrate the functioning of the earth's magnetic field and magnetosphere.
3. Scientific Significance:- Provide insights into atmospheric physics, plasma dynamics and solar terrestrial relation.
4. Importance for technology:- Aurora event often accompany geomagnetic storms that can affect satellites, ISS, GPS, radio communication, power transmission, etc.
5. Ecommerce and tourism value:- Auroras attract millions of tourist to the countries of north like Canada, Norway, Iceland, Finland to watch northern lights specially in the months of November to February. In southern hemisphere tourist visit Chile, Argentina, New Zealand, etc. in the months of May to August.

Conclusion

Continental Drift Theory

Concept of Continental Drift Theory

• Around 250 million years ago all land masses formed one giant super continent called Pangea.
• Pangea was surrounded by a super ocean called Panthalassa.
• A shallow sea was formed when Pangea got divided into 2 parts. The northern part of Pangea, situated north to Tethys sea was called Laurasia and the southern part was called Gondwanaland. Northern part is also known as Angara land.
• Further rupturing of Laurasia formed North America and Eurasia.
• Further rupturing of Gondwanaland formed South America, Africa, Antarctica, India, Australia and Madagascar.
• Because of rupturing of continents and their respective movement formed different oceans also like:-
  • Between North America and Eurasia intrusion of Panthalassa water formed North Atlantic and later on South Atlantic was formed between America and Africa.
  • Indian ocean was formed between Africa, Australia and Antarctica.
  • Artic ocean was formed when the Panthalassa water near North pole was surrounded by North America and Eurasia almost from all the sides.
  • Pacific ocean i.e. largest ocean on the plant is remanent of the old Panthalassa.
• Over geological time due to fragmentation of the land masses and their gradual shift has led to the present arrangement of the continents.
• Wegener believed that the continents are composed of lighter rocks i.e. silica and aluminium, floating over dense oceanic crust which is made up of silica and magnesium allowing them to move.

Evidences supporting this theory

1. Jigsaw fit of continents:- The coastlines of continents appear to fit together like pieces of a puzzle. e.g. the eastern coast of Brazil/South America matches closely with the western coast of South Africa. The best fit is obtained by matching continental shells rather than present coastline. This suggested that these 2 continents where once joint.
2. Geological Evidence:- Rock formation and mountain belts of similar age and composition are found on opposite side of ocean e.g. the Pre-Cambrian rock formations occur in Africa and South America. These similarities indicate a common geological stream Similarly the Appalachian mountain of North America continue into Norway also a part of Caledonian mountain range. It suggest that these mountains were formed when North America and western Europe were together.
3. Fossil Evidences:- Identical fossils are found on continents now separate by oceans. e.g.
   1. Mesosaurus:- Fossil of Mesosaurus are found in South America. It was a fresh water reptile. It could no have crossed the Atlantic ocean.
   2. Lystrosaurus and Cynognathus:- Their fossils are found across multiple southern continents. Though these were land reptiles and unable to swim.
   3. Glossopteris:- It is fossil of a plant/fern found in India, Australia, Antarctica, Africa and South America. However, this plant grows in old climatic conditions. Such fossils distribution strongly suggest that these continents were once connected.
4. Paleoclimatic Evidence:- Evidence of ancient climates also support continental drift. e.g. Permo-Carboniferous glacier deposit are found in India, South Africa, Australia, South America and Antarctica. These regions are now widely separated but once was part of Gondwanaland near the south pole. Other e.g. the presence of vast coal deposit in Russia, Kazakhstan, US, UK (near Atlantic region) and in Antarctica. Coal forms in warm humid conditions indicating these areas were once located in different climatic zones.
5. Presence of Gold Placer Deposits near Guinea coast of Africa:- Many river carry gold deposits/minerals and deposits into the sea but gold reserves are not found along with western African coast instead these are found in Brazil. If we put jigsaw fit evidence and the presence of gold placer deposits along with the fact that gold reserves are found in Brazil then it clearly becomes evident that these two continents were together in their geological past.

Forces Responsible for Continental Drift

1. Rupturing of Pangea
2. Movement of continents form pole to equator
3. Movement of continents to the west like North America and South America For rupturing of Pangea he made tussle between the gravitation and force of buoyancy responsible.

• According to him since these two forces act in the opposite direction and gravity is more powerful force thus Pangea ruptured about 200 million years ago.
• Pole-Freeing Force:- It is caused by earth's rotation it is basically centrifugal force due to which continents were believed to move from the pole to equator like India, Africa, Eurasia, etc.
• Tidal Force:- It is generated by gravitational attraction of sun and moon which rise in the east and set down in west because of the earth rotates from west to east.

Limitations of Continental Drift Theory

1. Inadequate explanation of driving force:- The theory could not explain that
   1. Why Pangea ruptured:- According to Wegener, it was because of tussle between the gravity and force of buoyancy but scientist have proved that it was a wrong interpretation. Gravity keeps the things intact.
   2. Pole free force was held responsible for continental drift from poles toward equator:- Scientist have proved that not only this force is too weak to move the continents but also it should also move the mass i.e. both continent and ocean floor instead of continents only as suggested by Wegener.
   3. The tidal force of sun and moon:- Which were made responsible for the west ward drift of the continent if taken seriously than this for should be 90,000 times greater than the present tidal forces of sun and moon and in such case it could have stopped the rotation of earth itself.
2. Apart form these limitations related to insufficiency of force he also lacked some conceptual clarity also e.g.
   1. According to him continents were drifting over the ocean floors this is conceptually wrong as plate tectonics has proved that is lithosphere slabs which are drifting over asthenosphere.
   2. Secondly he tries to explain the formation of folded mountains and island arcs or archipelago. To explain these he said that when continents were drifting over ocean floor where fractional resistance along their leading margin that's why continents got folded and mountains were formed. Island arc are those continental part found at trailing margin of the continents which could not match the rate of the drift of the moving continents e.g. Japan, Indonesia, Caribbean Island.

Conclusion

Plate Tectonics Theory

Plate tectonics is the theory which studies plates and various tectonic activities which take place along with plate margin. This theory was given in 1960s by Tuzo Wilson who quant the termed Plate, Dan Mackenzie, Woolrich Morgan, Arthur Holmes, Harry Hess. According to this theory, earth's outer rigid layer called lithosphere is broken into several large and small slabs which are called plates. These plates floats and move slowly over the semi molten layer beneath them called asthenosphere. Due to this plate movement several plate margin are formed along with the various tectonic activates like earthquake, volcanism, mountain buildings ocean trenches. mid oceanic ridings are formed.

Types of Plates

• On the basis of their constituents
  1. Continental Plate
  2. Oceanic Plate
  3. Oceanic cum Continental Plate
• On the basis of their size
  1. 7 Major Plates are
     • North American Plate
     • South American Plate
     • African Plate
     • European Plate
     • Indo-Australian Plate
     • Antarctician Plate
     • Pacific Plate
  2. 20+ Minor Plate
     • Juan-de-fuca
     • Coscos Plate
     • Carrabin Plate
     • Nazca Plate
     • Scotian Plate
     • Somalian Plate
     • Arabian Plate
     • Turkish Plate
     • Barman Plate
     • Philippine Plate
     • Bismarck Plate

Distribution of Plates

Plate Margin

1. Constructive Plate Margin It is formed when two plates move apart due to divergence. Two convectional currents operating beneath lithosphere in asthenosphere due to this 1. Fissure eruption of volcano occurs 2. Mid oceanic rigs are formed e.g. MOR of Atlantic 3. Earthquakes on mild magnitude occurs

   

2. Conservative Plate Margin Conservative plate margin are those one where two plates neither come close/ converge nor diverge/ move apart. Two plates simply slide pass to each other that's why there is construction or destruction either. It only develops
   1. Transform faults
   2. High Magnitude earthquakes
   3. No volcanism e.g. San Andras fault of North America.

      

3. Destructive/Convergent Plate Margin Destructive plate margin or convergent plate boundary develop when two plates move towards each other in this case three possibilities:-
   1. Continental and Oceanic Plate Convergence In this case
      • central eruption of volcano develops e.g. Mt. Stromboli of Italy.
      • folded mountains are formed e.g. Andes mountains were formed due to plate convergence between South American plate and Nazca plate.
      • high magnitude earthquake

        

   2. Oceanic and Oceanic Plate Convergence When two oceanic plate converge relatively heavier plate subducts under lighter plate due to this
      • Island arcs are formed and sometimes festoons also.
      • Central eruption of volcano e.g. Mt. Fuji of Japan, Mt. Mayon and Mt Tall Philippines, Mt. Krakatoa of Indonesia.
      • High Magnitude earthquakes and Tsunami e.g. 2004 tsunami was due Indonesia, 2011 tsunami was due to Japan
   3. Continental and Continental Plate Convergence When two continental plate convergence relatively heavier plate abducts beneath lighter plate due to this
      • High mountain ranges are formed. e.g. The Himalayas.
      • No volcanic eruption because
        • Thickness of the lithosphere become almost double due to abduction
        • Due to lack of water steam support to rising magma is very weak.
        • Rising magma is very vicious.
      • High Magnitude earthquake.

        

• Indonesia

• Indonesia is located where several plates meet that Indo-Australian Plate, Eurasian plate, pacific plate and Philippines plate.

• Formation Process of Indonesia

  Stage 1- Subduction of Indo-Australian Plate: The oceanic part of the Indo-Australian plate move northward. It subducted beneath the Eurasian plate Stage 2 - Formation of Ocean Trenches e.g. Java Trench and Sunda Trench Stage 3 - Magma generation: Subduction of plate in asthenosphere led to its melting and formation of magma Stage 4 - Development of Volcanic arc: Magma rose to the surface and formed Volcanic islands like Sumatra, Java, Bali, Lompoc, etc. Indonesia is world largest archipelago. It has about 17000+ island, over 120 active volcanos and experiences frequent earthquakes and tsunami due to active subduction.

• Formation Process of Philippines

  Philippines lies at the junction of Philippine plate, Eurasian plate and Sunda plate Stage 1 - Oceanic plate convergence: The Philippine sea plate and parts of the Eurasian plate moved toward each other. One heavier oceanic plate began subducting beneath the other. Stage 2 - Formation of deep Trenches: Subduction created deep ocean trenches such as Merina trench, Mindanao trench. Stage 3 - Magma Generation: The descending plate released water into mantle partial melting occurred. Magma rose through volcanos. Stage 4 - Volcanic Islands are formed: These islands merge and grew into larger islands such as Oleson. Philippines have move than 7000 island and numerous active volcanos.

Force responsible for plate Tectonics

1. Ritch push force: This force is applied by the magma rising through the divergent plate boundary
2. Slab Pull: When a subducting plate enters into asthenosphere it pulls rest of the plate inside.

Evidences of Plate Tectonics Theory

1. Sea Floor spreading
2. Palaeomagnetism
3. Hot spots (Volcanos)

Sea Floor Spreading and it's support to Plate Tectonics Theory

Mechanism of sea floor spreading

• Upwelling of magma occurs due to convection currents in the mantle.
• New oceanic crust is created at the mid oceanic ridge.
• Older crust moves outward symmetrically.
• Oceanic curst is eventually destroyed at subduction zone or ocean trenches.

Evidences supporting Sea floor Spreading.

1. Age of Oceanic Crust:- Rocks near the mid-oceanic ridges are younger while those farther away are older.

   

   It clearly suggest that gradual spreading of the sea floor is a reality.
2. Thickness of Sediments:- Marnie sediments are thinner near mid-oceanic ridge and thicker away from them because older crust has had more time to accumulate sediments.

   

3. Palaeomagnetism:- Alternating magnetic bands on either sides of ocean ridges record periodic reversal in earth's magnetic field. The symmetrical arrangement proves continues creation and outward movement of oceanic crust.

   

Palaeomagnetism

Process of Palaeomagnetism

• Earth behaves like a giant magnet with north and south magnetic poles.
• Molten rocks containing magnetic minerals align with earth's magnetic fields during cooling.
• Once solidifies after getting magnetic polarity, magnetic orientation is preserved permanent. It does not change unless the rock is exposed to higher temperature beyond 600^oC (Curie Point).
• Over geological time reversal in earth's magnetic field create distinct magnetic patterns in rocks.

Evidences from Palaeomagnetism

1. Magnetic Reversal:- Geological studies revelled alternating bands of normal and reversed polarity on the ocean floor. These magnetic strips occurs symmetrically on both side of mid oceanic ridges providing continuous formation of outward movement of oceanic crust.
2. Age and Magnetic Patter corelation:- The age of rocks increases with distance from mid-oceanic ridges while magnetic patterns remains symmetrical. These confirms sea floor spreading and movement of plates.
3. Evidence of Continental movement:- Palaeomagnetic data showed that continents such as south America and Africa were once joint and later drifted apart.

Role in supporting Plate Tectonic Theory

Hot spots and their role in supporting plate tectonics

Hot spots are localized zone of intense volcanic activity caused by rising plumes of hot magma from deep within core-mantle boundary and this is called mantle plume. Unlike ordinary volcanos formed at plate boundaries, hot spots may occur in the interior of tectonic plate. This concept was explained by Tuzo Willison and became important evidence for plate tectonics. A hot spot remains relatively stationary while tectonic plate move over it. As the plate shifts successive volcanos are formed, creating chains of volcanic island and sea mounts (Volcanic mountains formed under water).

Mechanism for hot spot activity

• The mantle flume rises from deep inside earth due to high temperature and low density.
• Magma reaches the surface through weak zones in the lithosphere.
• Volcanic eruptions create island or volcanic mountains.
• As the tectonic plate moves, older volcanos become inactive and new volcanos formed above the hot spots.

Evidences from hot spots

1. Volcanic island chains:- Chains of volcanic island show a clear age progression. The youngest volcano lies above the active hot spot, while older volcanos are farther away.
2. Direction and speed of plate movement:- The orientation and age of volcanic chains helps scientist determine the direction and rate of tectonic plate movement.
3. Evidence independent of plate boundary:- Hot spots occur even within the plates proving the plate themselves are moving rather than volcanic zone shifting. Good example of hot spot are Hawaii hot spot of Pacific, Reunion hot spot of Indian Ocean, Icelandic hot spot of Atlantic ocean, Yellow stone park hot spot of US.

Earthquakes

Earthquakes which are deep shaking in the earth surface are basically caused when a massive exogenic force converts huge amount of potential energy to kinetic energy. This energy flows in the form of seismic waves through the medium of earth surface and cause deep shaking.

Causes of Earthquakes

1. Tectonic Movement:- The Earth's lithosphere is divided into several tectonic plates that are constantly moving due to convection currents within the mantle. These movements occur at convergent (destructive), divergent (constructive), and transform (conservative) plate boundaries. As plates interact, enormous stress accumulates in rocks along faults and plate margins. When this stress exceeds the strength of the rocks, they suddenly break or slip, releasing energy in the form of seismic waves and causing an earthquake. Tectonic movements are responsible for the majority of earthquakes worldwide, particularly around the Pacific Ring of Fire, the Himalayan region, and major fault systems such as the San Andreas Fault.
2. Volcanism:- Volcanic activity can generate earthquakes due to the movement of magma beneath the Earth's surface. As magma rises through cracks and fissures, it exerts pressure on the surrounding rocks, causing them to fracture and produce seismic tremors. Explosive volcanic eruptions may also trigger earthquakes by the sudden release of gases and magma. These earthquakes are generally localized around volcanic regions and are often known as volcanic earthquakes. They commonly occur near active volcanoes such as Mount Etna, Mount St. Helens, and Kilauea.
3. Isostatic Adjustment:- The earth's crust sometimes rises or sinks to maintain balance after nature changes in the weight on the surface e.g. when glaciers melt after an ice age, the enormous pressure on the crust decrease. The crust slowly rises upward, causing a stress within the rock. This process is called isostatic adjustment. The release of this stress may produce earthquake e.g. Greenland is experiencing earthquake very frequently due to melting of the glaciers which is caused by global warming.
4. Elastic Rebound:- Earth crust stores huge amount of energy. The sudden release of stored energy causes earthquake. Actually earth crust is made of several layers and this is part of the plate. Tectonic forces continuously exert stress on rocks along fault lines, destructive plate, constructive plate and conservative plate margin. These rocks deform elastically and store strain energy over time. When the accumulated stress exceeds the strength of the rock they suddenly fracture or slip along the fault. The stored energy is then released in the form of seismic waves, causing an earthquake. After the rupture the rock rebound to less deformed state. Actually this is the factor responsible for most of the earthquake which occur along with fault lines worldwide.
5. Heavy landslide or Avalanche:- Large land slides or avalanche also trigger earthquake when a huge mass of rock or ice suddenly moves down mountain slope due to gravity they create deep shaking in the earth surface. It is very important cause of earthquake in hilly areas specially. e.g. Uttarkashi, Chamoli, Pithoragarh district of Uttarakhand.
6. Meteoritic Hit:- Sometimes meteors of extra-ordinary large size hits earth surface e.g. a meteor hit earth near Mexico about 65 million years ago, it causes supermassive earthquake, supermassive tsunami led to the extinction of dinosaurs.
7. Mining Activities:- Mining operation involves drilling, blasting and removing large quantities of rocks and minerals beneath earth surface. These activities weaken underground rock structure and disturb natural balance of pressure withing the crust. Sudden collapses or explosions inside mines can produce deep shaking and small earthquakes. Many mining regions on India like Bastar plateau, Chhota Nagpur plateau, Karnataka plateau keep on experiencing minor earthquakes.
8. Reservoir Induced Seismicity:- The construction of huge dams creates artificial reservoir containing massive amount of water. The weight to this store water exert pressure on the earth crust below. Water can also seep into cracks in rocks, reducing friction and increasing the possibility of movement along faults. This phenomenon is called reservoir induced seismicity. Several earthquake around the world have been large dam projects. e.g. Koyna dam in Maharashtra. (Koyna is tributary of Krishna)
9. Nuclear explosion:- Underground nuclear test release enormous amount of energy in a very short time, this energy create minor earthquakes.

Types of Earthquake Waves

1. Body Waves:- It originates from focus and moves thorough the inner layers of earth. They are faster than surface waves. These are of two types
   1. Primary Waves:- P waves are called primary waves because they travel the fastest and arrived first at seismic station after an earthquake occurs. It has following properties.
      • It carries maximum energy.
      • It has shortest wavelength.
      • It has maximum speed.
      • It travel through solid, liquid and gaseous medium.
      • It is longitudinal wave because it causes particles of the medium to vibrate parallel to direction of propagation.
   2. S Wave:- S waves are called secondary waves because they arrive after p waves.
      • These wave move in side to side or up or down motion i.e. perpendicular to the direction of propagation.
      • Its wavelength is longer and velocity is slower than p wave.
      • It can only travel through solid medium.
      • It produces stronger shaking than the p wave.
      • It is a transverse wave.
2. Surface Wave:- Surface wave originates from epicentre. Epicentre is a point on the surface which is nearest to focus. Types of surface wave
   1. Love Wave:- Love waves moves the ground horizontally from side to side. They do not create vertical movement. It travel faster than Rayleigh waves. It is name after British Mathematician AEH Love. It is also a transverse wave.
   2. Rayleigh Wave:- Rayleigh waves move like a wave originating in water if a pebble is thrown into it that's why these have rolling and circular motion. These have slowest speed and responsible for most severe damage.

Measurement of Seismic Waves

Mercalli Scale

Properties of Mercalli Scale

• It measures earthquake intensity and damage.
• It is based on observation and effects.
• It uses roman numerals from I to XII
• It varies from place to place for same earthquake, depends on population density and efficiency of disaster management.
• Useful for understanding earthquake impact on society.
• The meaning of I on this scale is not felt except by instruments, where XII means extreme destruction.

Richter Scale

Properties of Richter Scale

• The Richter scale is based on amplitude of seismic waves recorded by a seismograph.
• It is widely used for measuring small and medium earthquake.
• It is logarithmic in nature. With every increase in number it causes much stronger difference between the 2 numbers is 31.5 times in terms of energy and 10 fold increased in amplitude. Meaning of 1 on Richter scale is the energy equivalent to the energy released by explosion of 1 kg of TNT (Trinitrotoluene) a kind of explosive. The difference between 1 and 2 is 31.5 times, difference between 1 and 3 is 31.5² and 1 and 10 is 31.5⁹ times.
• This scale is ranges from 1 to 10 but its upper limit is not fixed it could be extended.
• Any earthquake occurring less than 3.5 on Richter scale is usually not felt by humans but felt by animals (specially reptiles).
• Any earthquake occurring 5.5. to 6 on Richter scale is less damaging.
• Earthquake occurring 6.1 onwards can be destructive. 8.0 and above are severally destructive.
• Richter scale is most frequently and widely used scale because of its scientific conclusion and high objectivity.

Moment Magnitude Scale

Properties of Moment Magnitude Scale

• It measure total energy released.
• More accurate for large earthquakes, use worldwide by modern scientist.
• It is based on seismic movement calculation.
• Does not saturate for powerful earthquakes.
• Provide consistent global comparisons.

Instrument used to measure Seismic Waves

Seismograph

Seismometer

Types of earthquake on the basis of depth of focus

Distribution of Earthquake

Circum Pacific Belt

Mediterranean-Himalayan Belt

Mid-Oceanic Ridge Belt

Seismic Map of India

1. New geological studies
2. Historical earthquake records
3. Seismological research
4. Tectonic movements
5. Scientific observations of seismic activities The National Centre of Seismology and other scientific organization also provide important seismic data in preparing and revising these maps.

Objective of Seismic Map

1. Identification of earthquake prone areas.
2. Safe construction practices.
3. Disaster management and planning.
4. Urban and Regional Planning.
5. Public Awareness and Safety.

Criteria Used for Seismic Zoning of India

1. Frequency of earthquakes.
2. Magnitude and intensity of earthquake.
3. Tectonic and geological conditions.
4. Nature of soil and rock structure.
5. Seismological studies by using modern instruments like satellite based observations and seismograph.
6. Historical damage records.

Seismic Zones of India

India is divided into four seismic zones based on earthquake hazard levels. Earlier there were five zones but zone I was removed after revision done by BIS. The present seismic zones are

1. Zone II It is low damage risk zone. It includes Karnataka, Tamil Naidu, Madhya Pradesh, parts of Rajasthan
2. Zone III Moderate risk zone. It includes Keralam, West Bengal, Maharashtra.
3. Zone IV High damage risk zone. It includes Delhi, Bihar, Punjab, Himachal Pradesh, Uttarakhand, south-western Maharashtra and parts of Gujrat.
4. Zone V Very high damage risk zone. It includes Jammu and Kashmir, Andaman and Nicobar and western Gujrat.

Some Important Terms

After Shock

Foreshock

Liquefaction

Seismic Gap

Isoseismal line

Volcanism

• Melting of rocks and magma formation in asthenosphere.
• Rises of Magma
• Ejection of magma into lithosphere/ Crust.
• Upwelling of magma on the surface. Types of material which comes out during volcanic eruptions

1. Water Vapour:- water vapour constitutes about 70% to 80% of the total material which comes out during volcanic eruptions.
2. Different Gases:- which includes carbon dioxide, sulphur dioxide, hydrogen sulphides, nitrogen. Volcanic eruption is most important natural source to contribute in sulphur dioxide in the atmosphere.
3. Lava:- Lava means molten rock. Molten rock beneath the surface called magma, when it reaches the surface it is called lava.
4. Pyroclastic Material:- Pyroclastic material are those one which are part of the surface which has been broken and flowing with lava.

   

Types of Volcanic eruptions

1. Central Eruption of Volcano:- It is called central eruption when magma upwells on the surface through a hole or vent. These are associated with destructive plate margin i.e. convergent plate margin when one oceanic plate converges with other oceanic and continental plate. The features of central eruption of volcano are:-
   • Magma erupts with burst.
   • The lava is highly viscous.
   • On pH scale lava is acidic.
   • Eruption process is highly explosive. On the basis of explosion intensity these are further categories into
     1. Hawaiian Type:- It is most gentle type of eruption.
     2. Strombolian Type:- It has moderate explosive activity.
     3. Vulcanian Type:- It is violent explosion.
     4. Pelean Type:- It is extremely violent explosion.
     5. Plinian Type:- It is most explosive type.
2. Fissure Eruption of Volcano:- When lava erupts thorough long crack or fissure instead of central vent it is called fissure eruption. These eruptions spread lava over a wide area. Properties of fissure eruption includes:-
   • These are associated divergent plate boundaries.
   • Lava is least viscous.
   • On pH scale lava is basic.

1. Active Volcano:- A volcano that erupts frequently or shows signs of activity is called active volcano. Other definition is that any volcano which has erupted during Holocene are called active volcanos. Good e.g. include
   1. Barren Island, Andaman and Nicobar. Only active volcano of India which lies 130km east of Andaman and it is process of eruption since 1990s
   2. Mt. Stromboli, Italy. It is called light house of Mediterranean sea
   3. Ojas-del-saldo, South America. One of the highest active volcano in the world.
2. Dormant Volcano:- A volcano that has not erupted for a long time but may erupt in future is called dormant volcano. e.g. Mt. Fuji, Japan, Mt. Kilimanjaro, Kenya Africa.
3. Extinct Volcano:- A volcano that has not erupted in historical times and is not expected to erupt again is called an extinct volcano. e.g. Mt. Kenya, Arthur's Seat

World distribution of Volcanos

Major Volcanic Belts of the world

Volcanos are mainly concentrated in three major belts:

Circum Pacific Belt

Volcanic eruption of 2026 in Pacific Ring of Fire

1. Axial Sea Mount - Oregon coast USA
2. Volcan - Oregon coast USA
3. Volcan-de-Fuego - Guatemala, a Central American Country
4. Bismarck Sea Eruption - Papua New Gini

Mid World Mountain Belt

Volcanic eruption of 2026

Mid Oceanic Ridge Belt

Hotspot Volcanos

Landforms formed by Volcanic Activities

1. Intrusive Landform:- Intrusive landform are formed when magma cools and solidifies below the earth surface before reaching on the surface. These landform are also called plutonic landforms because the cooling occurs slowly underground, intrusive rocks usually have large crystals. These are made up of granite mostly.

   

   Major intrusive landforms are
   1. Batholith are mass of intrusive rock formed deep inside the crust e.g. Ranchi Batholith
   2. Laccolith are dome shaped intrusive body looks like mushroom e.g. Henry Mountains
   3. Lopolith are saucer shaped intrusive landform e.g. Bushveld Igneous Complex.
   4. Phacolith are lens shaped intrusive landform. It occurs in anticlines and synclines of the rocks.
   5. Sill are horizontal layer of magma.
   6. Dyke are vertical layer of magma/ igneous rock.
2. Extrusive Landforms:- In central eruption of volcano magma comes out through a hole which is called mouth. and in fissure eruption of volcano it comes through a deep crack i.e. called fissure.
   1. Crater is large mouth
   2. Caldera is a very very large mouth which is formed through implosion.
   3. Nested Caldera is formed when large caldera is filled with small mouth or cone, formed due to small eruption of successive volcanic activity. It seems like a large nest of bird is filled with eggs.
   4. Crater like if formed when creator or caldera of extinct volcano is filled with rainwater or flood water.

Miscellaneous Terms

Hot springs, geysers, fumarole, solfatara are known as secondary volcanic features because they are produced by volcanic heat after the volcanic activity declines.

Hot Spring

Formation of Hot Spring

Geyser

Fumarole

Solfatara

Mud Volcano

Mountains, Plateaus and Plains

Types of Landforms

1. Primary Landform:- Continents and Ocean Basins
2. Secondary Landform:- which are formed upon continents and ocean basins like mountains, plateau and plains
3. Tertiary Landform:- which are formed upon mountains, plateau and plains like river deltas, beaches, etc.

Mountains

Folded Mountains

Process of formation of Folded Mountains according to plate tectonics

1. Deposition of Geosyncline:- Geosyncline is a long narrow subsiding basin where these layers of sediments accumulate over millions of years. Rivers and winds bring sediments into to basin gradually sediments became every thin due to continues deposition.
2. Movement of Plates:- According to the plate tectonics theory, the earth crust/ lithosphere is divided into plates that move slowly when two plates converge strong compressional force develops and sedimentary layers of geosyncline are squeezed.
3. Folding of Sedimentary Rocks:- Due to compression rocks layers bend into folds and gradually these folds develop into folded mountains.

Types of Folded Mountains

1. Old Folded Mountains:- These were formed before the rupturing of this Pangea. It includes
   1. Appalachian Mountains
   2. Norwegian Mountain
   3. Ural Mountain
   4. Pennine Mountain
   5. Drakensberg Mountain
   6. Aravalli
   7. Tien-Shan Mountain, etc.
2. New Folded Mountains:-
   1. Andes, South America
   2. Alps, Europe (France, Germany, Switzerland)
   3. Apennine, Italy
   4. Pyrenees, between France and Spain
   5. Dinaric Alps, Along with eastern coast of Acratic Sea
   6. Kunlun Mountains, China
   7. Himalayas, Asia
   8. Arakan Yoma, Myanmar
   9. Southern Alps, New Zealand

      

Block Mountains

1. Narmada Rift Belt between Vindhya Range and Satpura Range
2. Tipu Rift Valley between Satpura Range and Ajanta Rang
3. Rhine Rift Valley between Vosges Range of France and Black Forest Range of Germany.

Volcanic Mountains

• These are formed along with plate convergence zone, central eruption like Mt. Stromboli.
• Formed along with plate divergence, fissure eruption e.g. Mid Atlantic Ocean Ridge-longest mountain range in the world (On the continents longest mountain range is Andes of South America)

Relic Mountains

Plateau

Plains

1. Plains formed by rivers are called Alluvial or Peneplain.
2. Plains developed by wind are called Pediplains.
3. Plains developed by coastal waves are called coastal plains.

Rocks and Rock Cycle

Igneous Rocks

• Igneous rocks do not contains layers.
• Igneous rocks do not content fossils.

Classification of Igneous Rocks

On the basis of formation environment

1. Intrusive Igneous Rocks:- Intrusive igneous rocks are called Plutonic rocks also which are formed due to slow cooling and solidification of magma beneath earth surface e.g. gabbro, granite
2. Extrusive Igneous Rocks:- These are formed when lava cools quickly on the earth surface e.g. basalt and andesite.
3. Hypabyssal Igneous Rocks:- These are formed at intermediate depth.

On the basis of their composition

1. Felsic:- Silica content is greater than 66% e.g. granite.
2. Intermediate:- Silica content is between 52-60% e.g. Diorite.
3. Mafic:- Silica content is between 45-52% e.g. basalt.
4. Ultramafic:- Silica content is less than 45% e.g. Peridotite.

Sedimentary Rocks

• Sedimentary rocks have clear layers.
• Sedimentary rocks contains Fossils.

Formation of Sedimentary Rocks

1. Weathering and erosion
2. Transportation of eroded material
3. Deposition of sediments
4. Compaction
5. Cementation

Types of Sedimentary Rocks

1. Clastic Sedimentary Rock:- These are formed from fragments of pre-existing rocks compacted and cemented together e.g. sandstone, shale.
2. Chemical Sedimentary Rock:- These are formed thorough chemical reaction, evaporation of water e.g. limestone.
3. Organic Sedimentary Rock:- These are formed from the accumulation of organic materials from plants and animals e.g. coal, chalk.

Metamorphic Rocks

• Metamorphic rocks have relatively high density and firmness.
• These have layers if metamorphism have taken out of sedimentary rocks e.g. anthracite coal.
• It has no layers if its formed out of igneous rocks.
• It may or may not contain fossils.

Formation of Metamorphic Rocks

1. High temperature i.e. 200^o to 800^o C
2. Pressure
3. Chemically active fluid like very hot water
4. Time because it take thousands to millions of years

Types of Metamorphism

1. Contact Metamorphism:- It is caused by heat from nearby magma.
2. Regional Metamorphism:- Large scale metamorphism during mountain building.
3. Dynamic Metamorphism:- Caused by faulting e.g. Vindhyan Range.
4. Hydrothermal Metamorphism:- Mostly in oceans.

Rock Cycle

Process and Transition in Rock Cycle

1. Igneous to Sedimentary:- When igneous rocks are exposed on the surface. These are subjected to weathering, erosion, transportation, cementation and compaction to form sedimentary rocks e.g. granite and sandstone.
2. Sedimentary to Metamorphic:- When sedimentary rock is subjected to high pressure or chemically active fluid due to burial or tectonic activity then the sedimentary rock is metamorphized e.g. limestone to marble, sandstone to quartzite, shale to slate.
3. Metamorphic to Igneous:- When metamorphic are subjected to high temperature beyond melting point e.g. gneiss to basalt and quartzite to basalt.
4. Igneous to Metamorphic:- It is formed when igneous rock is subjected to high temperature and pressure below melting point e.g. granite to gneiss and basalt to amphibolite.
5. Sedimentary to Igneous:- When sedimentary rocks are exposed to high temperature beyond melting point e.g. sandstone to diorite.
6. Metamorphic to Sedimentary:- When metamorphic rock is subjected to erosion, transportation, deposition and cementation e.g. marble to limestone, quartzite to sandstone and eclogite to mudstone/shale.

Weathering and Erosion

Types of Weathering

Physical Weathering

1. Thermal Expansion:- Rock expand or contract due to temperature changes causing stress and cracking.
2. Frost Action:- Water enter cracks in rocks, freeze, expands and factures the rocks.
3. Exfoliation:- Outer layers of the rocks peel away due to pressure release as overlaying burden of material is eroded. Exfoliation is also called onion weathering. It is mainly associated with granite rocks.

Chemical Weathering

1. Oxidation:- Iron bearing minerals react with oxygen forming rust like compounds.
2. Carbonation:- Carbonic acid i.e. CO₂ + H_{2O react with minerals specially with calcium carbonate rocks and breakdown the rocks.}
3. Acid Rain:- Rainwater reacts with sulfur dioxide, nitrous oxide and forms sulfuric acid and nitric acid respectively. When it react with mineral present in the rock it is broken down.
4. Dissolution:- Minerals dissolve in water specially in acid water easily e.g. calcite minerals present in limestone dissolve in rainwater easily.
5. Hydrolysis:- Water reacts with minerals, forming new minerals like clays e.g. feldspar in granite turns into clay.

Biological Weathering

1. Root Wedging:- Plant roots grown into rocks cracks, prying them apart.
2. Burrowing:- Animals which live in soil break apart the rocks, exposing them to further weathering.
3. Organic Acid:- Lichens, Mosses or microbes secrete acid that chemically alter rock surface.

Importance of Weathering

• It is most initial stage for the breaking of rock. It is usually necessary to support erosion. We know most of the erosional agents like water, wind, coastal waves are not very effective agent of erosion in their purest form. Weathering process provide require amount of sediments which acts as instrument of erosion.
• Weathering process is responsible for formation of various types of soil e.g.

Erosion

1. Water Erosion:- It is most prevalent type of India caused by rain water, river water etc. This erosion id done by applying frictional force, attrition (collision of rocks with each other), saltation when rocks and the pebbles flow with water along with river belt while jumping and falling.

   

2. Wind Erosion:- Wind erosion includes
   1. Suspension:- Fine particles are carried long distance in air.
   2. Saltation:- Medium size particles bounce along the surface
   3. Surface Creep:- Large particles roll along the ground.

Landforms

• Fluvial or river landform
• Aeolian or wind landform
• Karst or groundwater landform
• Coastal waves
• Glacier landform

Fluvial Landform