Geography

The Earth Origin and Evolution

  • One of the earlier and popular hypothesis about the Origin of Earth was
    • Nebular Hypothesis
  • The Demonstrator of nebular hypothesis was
    • German Philosopher Immanual kant.
  • It was revised by Laplace in 1796.
  • The hypothesis considered that the plants were formed out of a cloud of material
  • associated with a slowly rotating Sun.
  • The “Binary theory was formulated by Chamberlain and Moultan in 1900.
  • Under this theory a wandering star and a material separated from the Solar surface revolve around the Sun and slowly condensed in to a planets.
  • This argument was suppoted by Sir. James Jeans and Sir.Harold Jeffrey.
  • In 1950 Otto schmidt and Carl Weizacar revised the “ Nebular Hypothesis”.
  • In Modern theories “the Origin of Earth” is replaced by “the Origin of Universe
  • The most popular argumrnt regarding the Orign of Universe is “the Big Bang theory”.
  • The Big Bang Theory was also called “Expanding Universe Hypothesis”. .
  • It was formulated by “Edwin Hubble is 1920.
  • Under Big Bang Theory considered the stages such as
    • 1) All matter forming universe existed in one place in the form of a “tiny ball” or singular atom with Unimaginably small volume, infinite temperature and infinite density.
    • 2) The volentery explosion of “tiny ball” at the Big Bang lead to a huge and continuous expansion.
  • As a result energy was converted in to matter.
  • The event of Big Bang took place 13.7 billion years before the present.
  • With in first 3 minutes from the Big Bang event , the First atom began to form.
  • With in 300,000 years from the Big Bang, the temperature dropped to 4500 kelvin.
  • The Universe became transparent.
  • The expansion of Universe means increase in space between the galaxies.
  • An alternate to the Big Bang theory was Hoyle‟s concept of steady state.
  • Under this concept the universe to be roughly the same at any point.
  • The scientific community at present favours the arguments of expanding Universe
  • The bases for development of galaxy was the differences in the gravitational forces due to the density differences between matter and energy in the early Universe.
  • A galaxy contain large number of stars.
  • The distance of galaxy are measured in light years.
  • A light travels at a speed of 300,000 km/second .At this distances the light will travel in One year is called One light year.
  • 1 light year = 9.461 x 1012kms
  • The mean distance between the Sun nad the earth is 149598 ,000kms , it is equals to “8.311” light years.
  • The diameters of individual galaxies range from 80,000 – 150,000 light years.
  • A galaxy starts to form by accumulation of hydrogen gas in the form of a very large cloud is called ”nebula”.
  • It grows in to denser gaseous bodies and giving rise to formation of stars.
  • The stars formation taken plate 5 – 6 billion years ago.
  • The stars are localised clumps of gas with in a nebula.
  • The planets are formed from planet esimals.
  • The planet esimals are small rounded objects developed from gas cores and matters by Cohesion.
  • Large number of small planet esimals accrete to form planets.

SOLAR SYSTEM

  • Solar system is supposed to be formed from “nebula” about 5 – 5.6 billion years ago and planets about 4.6 billion years ago.
  • Our Solar System consist of the sun ,8 planets, 63 Moons , millions of smaller bodies like asteroids , comets and huge quantity of dust grains and gases.
  • The planets lie between the Sun and the belt of asteroids are called “ inner planets”.
  • Out of ‘ 8 ‘ Planets ‘ 4 ‘ are Inner planets.
  • They are Mercury , Venus ,Earth and Mars.
  • The other planets are called outer planets.
  • They are Jupiter , Saturn ,Uranus and Neptune.
  • The Inner Planets are also called Terrestrial Planets means earth – like , because they are made up of rocks and metals.
  • The outer planets are also called Jovian planets Or Gas – giant planets.
  • Jovian means Jupiter – like
  • Most Jovian planets are larger than terrestrial and have thick atmosphere with Helium and Hydrogen.
  • In a meeting of the international Astronamical union take a decision that recently discovered Pluto like celestical objects “2003 UB313 “ may be called “dwarf planet”.
  • The terrestrial planet formed in the close vicinity of the parent star where it was too warm for gases to condense to solid particles.
  • Jovian planets formed a quiet distant location.
  • The solar wind was most intense and blew off lot of gas and dust particles from the terrestrial planets.
  • The Solar wind was not much intense in jovian planets.
  • The terrestrial planets are smaller and their lower gravity could not hold the escaping gases.

The Moon

  • It is the only natural satalite of the earth .
  • Many Scientists attempted to explain the orign of Moon.
  • In 1838, According to Sir George Darwin the Moon and Earth formed a single rapidly rotating body at beginning and gradually it broken.
  • The modern scientists not accepted this theory.
  • It is now generally believed that the Moon was formed due to an outcome of “giant impact”or” the big splat” about 4.4billion years ago.

The Solar System (The planets)

PlanetDistance from Sun in Astronomical UnitsDensit in (gm/cm^3)RadiusNumber of Satelites
1Mercury0.3875.440.3830
2Venus0.7235.2450.9490
3Earth15.51711
4Mars1.5243.9450.5332
5Jupiter5.2031.3311.1916
6Saturn9.5390.709.46018
7Uranus19.1821.174.1117
8Neptune30.0581.663.888
  • Average mean distance of earth is 149598.00km = 1Au , Radius , 1 Equatorial radius =6378.137kms.

India – Evolution and Geological Structure

  • Geologically the Indian subcontinent was a part of the gondwana land or the Southern continent.

Major Geological formation

I) The Archean Formations

  • It is also known as the pre Cambrian period.
  • It denotes the geological scale from the formation of earth to the beginning of Cambrian period.
  • That is about 4.6 billion years ago to 570million years ago.
  • The Pre Cambrian time constitute about 86.7% of Earth history.
  • The term ‘Archaen’ was introduced by J.D.Dana in 1782.
  • The oldest known rocks of the earth was from this period.
  • The Archaen rocks are Unfossiliferous or azoic.
  • These rocks are known as the “ Basenent Complex or fundamental gneisses ”.
  • According to T.S Holland , Indian geological time scale the Pre Cambrian Era is known as the Purana.
  • The Archaen system includes the Arawalli, Dharwar , Cuddapah , Vindhya ,Meghalaya ,
  • Plataeu ,and Mikir hills and also called Archeaen gneiss.
  • The Constituant minerals of Archaen gneiss are Arthoclase , Oligoclase , Quartz ,muscovite ,biotite and horn blends.
  • The Archaen rocks cover 2/3rd of Peninsular India.
  • They are known to be ‘ 3 ‘ types .

(A) The Bengal Gneiss

  • Highly foliated , located in the Eastern Ghats, Odisha , Manhum and Hazaribagh of Jharkhand , Nellore of Anadhra predesh and Salem of Tamil nadu.
  • For the First time this type of rocks were identified in the Miduapur districts of West Bengal.

(B) The Bundle Khand Gneiss

  • Massive granitoid and the second group of fundamental gneiss of the Archaen age.
  • It occurs in Bundel Khand in U.P, Banghel khand in Madhya Pradesh , Maharashtra,Rajastan, Andra predesh and Tamil Nadu.
  • It is coarse grained and looks like granite, Criss crossed and characterized by Quartz Veins.

(C) The Nilgiri Gneiss

  • Massive ,eruptive dark – coloured gneiss.
  • It is bluish – grey to dark coloured rock ,medium to coarse grained in texture.
  • It is becoming to the Charnockite series.
  • It occurs in South Arcot , Patni Hills,Shevaroy Hills and Nilgiri in Tamil Nadu, Nellore in Andhra Pradesh ,Balase in Odisha ,Kerala ,Malabar ,Jharkhand, Chattisgarh and Aravallis in Rajastan.
  • The Archaen rocks are rich in farrous and non – ferrous minerals like ironcore , copper,Manganese, Mica ,dolomite lead ,Zinc silver and gold.

II) Dharwar system or protozoic formations

  • The first metamorphosed sedimentary rock system in Indian geological Time scale.
  • These type of rocks were studied for the first time in India was Dharwar districts of Karnataka.
  • These rocks are highly metalliferous.
  • Rich in iron ore , Manganese , lead ,Zinc,gold , Silver ,dolomite,Mica ,Copper , Tungsten,Nickel, precious stones and building materials.
  • Important serious Dharwar system are

a) Champion serious

  • Named after the champion reef in the Kolar gold fields.
  • The gold content in this series is about 5.5per tonne of ore.

b) Cham paner series

  • An outlier of the Aravalli system of vadodra.
  • Consist of quasrtzites , Conglomerates, Phylites ,states, lime stones and marbles.
  • An attractive green variety of marble is obtained from this series.

c) Chilpi series

  • Occupies Balghat , Jabal pur and Chindwana districts of Madhya Pradesh.
  • It consist of graint , phylite ,Quartzite, green stones and magniferous rodes.

d) Closepet series

  • A Dharwarian formation found in the Balghat and Chindwana districts of Madhya Pradesh.
  • It consist of quartzite ,Copper phrites and magniferous rodes.

e) Iron – Ore series

  • Occures in Sigbhum, Bonai, Mayur bhanj and Keonjhar.
  • It Supplied iron ores to Jamshedpur , Durgapur, Rurkela and Bokaro steel plants.

f) Khondolite series

  • Occupies in Eastern ghats.
  • It consist of Khondolites , Kodurites , charnockites, and gneisses.

g) Rialo series

  • It is also called Delhi series.
  • It extends from Delhi to Alwar in Rajastan.
  • It is rich in lime stone , Makrana marbles.
  • The high quality of Marbles in Makarana and Bhagwan pur are belonging to this series.

h) Sakoli series

  • Stretching over Jabal pur abd Rewa districts.
  • Rich in Mica , dolomite , Chist and Marbles.
  • The marbles of this series are of Super quality.

i) Sausar series

  • It spreads over Nagpur ,Bhanadra in Maharashtra and Chindwara in MadhyaPradesh.
  • Rich in quartzite , Mica chist ,marbles and Magniferous rocks.

III) The Cuddapah system or the Purana Group

  • Made of shales ,slates ,lime stone and quart zite.
  • Rocks are mostly without Fossils.
  • These are sedimentary – Metamorphic formation, It is named after the Cuddapah in Andra Pradesh.
  • It occurs in the Cuddapah ,chattisgarh , Rajastan, Delhi to the South of Alwar and the Lesser Himalayas.
  • The rocks of this system are sandstone ,shales,lime stones, quartzites,slates,iron ore,asbestos, copper,nickel ,cobalt,marbles, Jaspers , building materials and stones for inferior decoration.

Papaghani series

  • It is named after the Papaghani river in Andra Pradesh the rocks were exposed from there.
  • It consist of quartzites, Sand stones,Shales, Slates ,lime stone and Marbles.

The Vindhyan System

  • It derives the name from the Vindhyan mountain , a dividing line between the Ganga plain and the Deccan plateau.
  • This system extends from chittorgarh in Rajastan to Sasaram in Bihar – 103600sqkms.
  • It is well known for red sand stone , sand stone ,building materials etc.
  • The diamond mines of Panna and Golconda lie in the Vindhyan system.
  • Qutabminar , Humayun‟s tomp,Fatepur sikri, Agoa fort Red fort, Jama – masjid, Birla mandir, Budhist stupa‟s of Sanchi – Constructed from the red sand stone of Vindhya Ranges.
  • Coarser Sand stones of this system used as grind stornes and mill stones.

Major series of Vindhyan system.

  1. Bhander series
  • It spread over the western parts of the Vindhyan formation.
  • Main rocks are Sand stones ,Shales , limes stones.

2. Bijwar series

  • It stretching over Chahtaspur and Punna.
  • Main rocks are Sand stones , read sand stones and quartzite.

3. Kaimur series

  • Spread over Bundelkhand in U.P and Bhagal khand in M.P.
  • Main rocks are Sand Stone , Conglomerate and shale.
  • Rich in red sandstone used

Major Geological Periods

The Palaeozoic Group / Cambrian to Carboniferous period

It includes Ordovician , Silurian , Devorian , Carboniferous and the Permian periods of the Geological Time scale.

In the Indian Geological Time scale this period is known as Dravidian Era

It extends from 570 million years ago to 24.5 million years ago.

It marks the beginning of life on the Earth‟s surface.

Its formations are absent in Peninsular India excepts near Umaria in Rewa.

At this period the Pangala was broken and the Tethys sea came in to existence.

The rocks of this periods were Shales , Sandstone , Clays , Quartzite ,States , Marbles etc.

The Me So Zoic Era / The Gondwana System

  • It denotes middle life.
  • Presence of Fossil invertebrates.
  • It includes three subperiods.
  • They were Triassic , Jurassic and Cretaceous.
  • In the Indian Geological time scale it extends from the upper carboniferous to the beginning of the Cenozoic Era or the Aryan Era.
  • In Standared Geological time scale the Gondwana group begins with the Permo – Cambrian period called a period of Coal formations.
  • Most of good quality coal deposits found in Gondwana formation.
  • The series of Gondwana system of Talcher in Dhankenal districts of Odisha is called Talcher series.
  • It is rich in good quality coal used for thermal power plant.
  • The series belongs to the middle Gondwana period with enormous deposits of coal seams are “The Damuda Series”.
  • This Coal seams are more thicker in eastern coal seams.
  • The major coal bearing areas of this period are Raniganj , Jharia , Karanpura and Bokaro of the Damodar basin.
  • Singrauli , Kobra and Pench valley in Chattisgarh and Madhya pradesh.
  • Talcher of Mahanadi basin in Odisha.
  • Singareni at Satpura basin in Madhya Pradesh.
  • The Jhingurda coal seam with a thickness of about 131cm is the thickest coal seam in India.
  • The Gondwana rocks are mainly found in india at
    • Himalayas from Kashmir to Arunachal Pradesh and Poorvachal.
    • Saurashtra , Kachch , Western Rajastan, corromandal and Rajmahal Hills.
  • The youngest series of the Lower Gondwana system is – The Panchet series.
  • Panchet is a hill in the south of Raniganj.
  • This series consist of greenish – sand stone and Shales.
  • The Gondwana system of rocks provided over 95% of the coal of India.
  • It also provides iron – ore , lime stone , sand stone and raw materials for ceramic industry.
  • India‟s largest coal deposits are found in the Gondwana system.
  • Mainly in the Damodar valley of West Bengal ,Jharkhand , the Mahanadi vally of Odisha and Chhattisgrah ,the Godavari valley of Andra Pradesh and the Satpura basin of Madhya Pradesh.

The Cretaceous / The Decan trap

  • This period extends from 146 million years ago to 65 million years ago.
  • The term „ Cretaceous‟ obtained from the latin “creta”means “Chalk”.
  • It is marked by the transgression of the Sea ,that is coromandel coast ,narmada valley and out pouring of huge quantity of lava basalt.
  • As a result formation of the Deccan Trap.
  • The Deccan trap is also called “The Lava Plateau is the result is the result of lava eruption”.
  • It covers about 5 lakh sqkms of area in Gujarat ,katch , Kathiawad – Maharashtra , Madhya Pradesh – Malwa Plataeu, Chhattisgarh, Jharkhand, Northern Andhra Pradesh and North – Western Karnataka.
  • The lava Plateau or Deccan Trap in india has a maximum thickness of about 3000m along the coast of Mumbai.
  • 800m in Kachch , 150m at Amar Kantak and 60m at Belgaum in Karnataka.
  • The Individual lava with an average thickness of about 5m to 29m near Bhusawal Maharashtra are interbedded with “inter trappean beds”.
  • In addition to Basalt ,Deccan trap is also rich in quartz, Bauxite , magnetite ,agate „Semi precious stones , Magnesium , Carbonate potash and Phosphates.

The Teri tiary system / the Cenozoic Era.

  • Cenozoic mean recent life.
  • Beginning of this period id about 65million years ago‟
  • The Cenozoic era has two periods.

a. The teritiary period

  • Two main events in this period were.
    • 1) The final breaking up of the Gondwana continent occurs.
    • 2) The uplift of Tethys geosycline in the form of the Himalayas.
  • The Upleaval of the Himalayas changed the old topography of the Subcontinent.
  • There were three phases in the Upheaval of the Himalayas.
  • 1) First Upheaval in the Ecocene period about 65million years ago and culminated in the Oligocene.
  • Resulted in the upheaval of the Greater Himalyas.
  • 2) Second Uphevel in the mid – Miocene period about 45 million years ago.
  • Resulted in the folding of Lesser Himalayas.
  • 3) Third Upheaval in the post – poliocene period, about 1.4milliom years ago.
  • Resulted in the folding of Shiwaliks or the outer Himalayas.
  • The Himalayas are still rising.

Peninsular region

  • The Tertiary system occurred coast of Kachchh, Kathiawar , Konkan , Malabar, Nilgiris and the Eastern Ghats.

b. The Quarternary period

  • It is the Pleistocene and recent formations.
  • Quarternary denotes very recent deposits.
  • The northern plains of India came in to existence during the Pleistocene period.
  • The Origin of thethird physical division of India ,the Great Indo – Gangetic – Brahmaputra plain in this period.
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