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Wednesday, October 24, 2018

Plate Tectonic


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Plate tectonic theory

The concept of plate tectonic has make established   ground in explaining many important problem of physical geology including mountain building, folding, faulting, seismicity, volcanism etc. The  theory of plate tectonic developed by Geo scientist during 1960s is described as a most revolutionary concept in the history of geology. The term plate was first used by J.T. Wilson in  1965  and result of continental drift theory of Wegener.  according to this concept the rigid lithospheric slabs or block and solid crystal plates are  called plate. The whole mechanism of evolution, nature and the motion of plates is known as plate tectonics. The rigid lithosphere is capable to moving bodily over the Asthenosphere( hot-plastic flexible layer of upper Mantle). There are  six major  and  20  minor plates  have been identified .About twelve of these plates have been so far distinguish and the name of twelve major and minor lithospheric plates under focus to study of Geoscientist e.g.

  • The Pacific plate,
  • The North American plate,
  • The South American plate,
  • The African plate,
  • The Antarctic plate,
  • The Indian Australian plate the European plate,
  • The Arabian plate,
  • The nazea plate,
  • The Caribbean plate,
  • The scotia plate and
  • The Philippines plate.
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  Plate tectonic theory is based in two major concepts
 (a)  The concept of continental drift   and
 (b) Concept of sea-floor-spreading.
The main ideas underline the theory of plate tectonics are the out-come to the   study   of the structure of the ocean-floor and the formation of young oceanic-crust in  mid oceanic ridge.  





 Chemical composition of interior


Related image

Inner part        Fe, Ni
Outer part       Fe, Ni + silica
Mental.           Olivine                                                       
Oceans.           Basalt
Mental.           Granite and Andesite 

Location of the rock
 example
Properties
Reaction (if we melting)
Mental

Olivine
Highly heaviest fluid
Mercury
Oceanic crust 

Basalt
Less heavier fluid
Water
Contcrustal crust

Andesite
Less mobile light fluid
Honey
Continental crust
Granite
Least mobile lightest fluid
Wax

 

 Movement  of  Plates


       Plates 

 Divergent boundaries
 Convergent boundaries
Transform boundaries
Similar Names

Constructive plate margin or accreting plate margin 


Destructive plate margin  or consuming plate margin

Shear plate margin or conservative plate margin

Cause

Ascending Limb of convection current beneath the earth's crust


Descending Limb of convection current beneath the earth's crust

Horizontal movement of convection current beneath the earth's crust

 Mechanism

Two plates are in the motion away from each other


Two plates are in the motion towards each other


Two plates are slide apart each other

Formation

Mid -oceanic -ridge, rift valley, shallow focus earthquakes and volcanic eruption 


Mountains formation and major earthquakes

Fault create and shallow focus earthquakes with horizontal slips

Examples 


North America plate Vs  Eurasian plate 


Indian plate and Tibetan plate 


San-Andres Fault










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