Geography Chap 2 (Goh Cheng Leong + NCERT)

Chap 2

The Earth’s Crust

Structure of the Earth:
--Lithosphere= Crust(Continental +Oceanic) + Upper part of “Upper Mental”.
--Crust=bottommost continuous layer “Basaltic AKA Oceanic”(SIMA = Silica + Iron + Magnesium) + non continuous layer(not in ocean) “Granitic AKA Continental”(SIAL =Silica +Alumina) layer above Basaltic.
--desnsity of “SIMA” > “SIAL” ===Density difference makes it appear, SIAL floating over SIMA.
--Mentle= below Crust(or below Lithosphere, which contains upper part of upper mental) = Dense rock “Olivine” = this layer is called Mesosphere.
Core= most interior layer + mainly made of “Nickle (Ni) + Iron(Fe)”---à(NiFe) …..this layer = Barysphere.
            >> Earthquake Wave (Seismic wave) study ====Earth core =Solid mass/ Crystaline.

Type of Rocks:
Igneous rock:
--Formation = cooling +solidification of “Magma.
--Identity = no layers + no fossils + normally crystalline .
--Property = hard + resistant to erosion ↑ = therefore used in “Polished stone” +”road making” etc.
--Type:
    >On the basis of MINERALs:
       >>Igneous rock with high proportion of SILICA = “ACID igneous rocks”
       >>Igneous rock with high proportion of “Fe + Al +Mg” = “BASIC” igneous rocks”
       >> Acid igneous rocks (Density) > Basic igneous rocks(Density)
    
   >On the basis of Origin:
       >>Plutonic rocks:
                >>>Magma solidifies inside earth’s surface = Annealing process.
                >>>As a result of Annealing process = Larger recognizable Crystals.
                >>>exposed to surface after denudation.
                >>>those which comes vertically and solidifies within layer = Dykes.
                >>>Horizontal solidification within earth surface = Sills.
                >>>Example = Gabbro, Granite, Diorite etc
(Plutonic rock types== image below ↓)


      >>Volcanic  rocks:
                >>>Solidifies outside the surface = Quenching process.
                >>>Quenching results in = Small crystals.
                >>> Example = Basaltic rocks.

Sedimentary rocks:
--Formation = from sediments accumulated over period + usually under water.
--identity = layers (Stratified rocks) + Non crystalline + usually fossils.
--Property = hard / soft depends on sediments forming it.
--Type:
     >on the basis of Origin:
          >>Mechanically formed sedimentary rocks.
               >>>Formed = materials of other rocks.
               >>>Example= Sandstone= derived from fragments of Granite sedimented with time.
                           >>>>many variety= diff grain size
                            >>>>use= grindstone + building etc.
            
           >>Organically formed sedimentary rocks.
                >>>Formed =Organic material(skeleton which remain undecomposed) =hard Shell + corals etc.
                >>> Example = Chalk + Limestone + Carbonaceous rock (diff Coal).
                >>> rich in calcium = calcarious in nature.

Metamorphic rocks:
--Formation = igneous/Sedimentary under Temp↑ + Pressure ↑.
       > Example of Metamorphosis :
       >Clay ==è Slate.
       >Limestone(organic +Sedimentary) ==è Marble.
       >Shell/Coal(organic +Sedimentary)==èSchist/Graphite.
       >Sandstone(Mech + Sedimentary)==è Quartzite.
       >Granite (Plutonic + Igneous)==è Gneiss.

Mountain building process:
--Orogenic movement = a mountain building process.
--On the basis of Time of origin
     >4 types of Mountain (Image below ↓):

--On the basis of formation process(4type):
    >Fold Mountain:
       >>Compressive forces =increased load (of overlying rocks)+Flow movement(Magma)+Magmatic intrusion into the crust+ Expansion or Contraction of some part of the earth
       >>Example =Himalayas, Rockies, Andes and Alps
       >>many active volcanoes (especially in Circum-Pacific mountain system)
       >>Minerals =Tin, Copper, Gold and Petroleum.

   >Block Mountain:
      >>Formation=Cracks(not fold) of crust submerges or raises.
    >>Forces= both Compressiv & Tensile.
    >>Tensile (fig a) = tension allows central block to subside==major reason for “Rift valleys” + Large block Mountain” ==African Rift Valley, Himalyas, Vosges and Black forest(Rhineland).
    >>Compression(Fig b) = allows to rise/subside ==less prevalent. ===Mountain ranges of Satpura+ Vindhyas(Central-Western India).

Volcanic Mountian:
--Identity= vents in various layers.
--example =Mt Fuji(Japan) + Mt Mayon(Philippines)+ Mt Merapi(Sumatra) + Mt Agung(Bali) + Mt Catopaxi(Equador) etc.


Residual Mountain:
--Formation= Mountain from denudation of sides near normal land.
--Fig below:

Plateau/Plateaux:
--AKA  Table land.
--Rich in Mineral:
     >Deccan Plateau = Manganese+ Coal +Iron.
     >Plateau of Western Australia =Gold + iron.
     >African Plateau = Gold + Diamond + Chromium + Copper + Manganese.
     >Brazilian Plateau= Iron + Manganese (specially “Minas Gerais area”)
    
--3 Types according to mode of formation.

Tectonic Plateau:
>Deccan Plateau =India
>Meseta of Central Iberia =Tilted Plateau
>Harz of Germany =Faulted Plateau.
>Plateau between Fold mountain = intermont plateau
>Intermount Plateau(mostly highest):
      >>Tibetan Plateau = between Himalaya + Kunlun.
      >>Bolivian Plateau= between Two ranges of Andes.

Volcanic Plateau:
--North-Western part of Deccan Plateau of India.
--Antrim Plateau =Northern Ireland.
--Columbia Snake Plateau =most remarkable = twice the size of Malaysia.

Dissected Plateau:
--formation= dissection from River stream + wind + Glacial flow.

Plains:
--Low lands = leveled or undulated .
--Types 3:
Structured Plain:
--formed by horizontally bedded rocks
--Example= Russian platform +Great plain of USA + central lowland of Australia.

Depositional Plain:
--Formed by deposition==erosion from adjacent highland.
--largest depositional plain = Rivers
–comparatively leveled ……rises gently toward near by highland.

Erosional Plain:
--eroded by river, wind etc.
--with time for ex- river erodes the highland and brings it to the level of near by region.