Plate tectonics Bhumika Saini
Prelude to plate tectonics . Continental drift .Sea floor Spreading Geomagnetism Plate tectonics theory
Continental drift Wegner wrote book Origin of continent and oceans in 1912 . Wegner wrote book .Premises A supercontinent existed Pangea near present Durbar Pangea surrounded by Panthalasa SIAL is floating over SIMA e Pangea surrounde . Northern part called laurentia and southern part gondwanaland . Pangea divded by a shallow and meandering water body - Tethys sea
Stages . Pangea stage (during carboniferous period) STAGE 1 Flight of continents(continents began to drift and break in Stage 2 pieces-Laurentia and gondwana) . Opening of tethys (The intervening space between laurentia and gondwana got filled with tethys sea and it widened) Stage 3 . Westward Drift( North and South america drifted westwards Stage 4 and altantic ocean opened) . Orogenetic Stage(Rockies and Andes formed) Stage 5
PANGAEA the large landmass that included all of Earth's present day continents LAURASIA Esastor SEA a. PERMIAN 225 million years ago TRIASSIC 200 million years ago JURASSIC 135 million years ago Equitor CRETACEOUS 65 million years ago PRESENT DAY
Forces Northward shift . Difference between force of buyoncy and graviational pull Tidal force of moon Westward shift
Evidences Continental Drift Theory Evidence for Continental Drift includes includes includes includes ntinenta Edges Rock Structures Same Fossils Climate fit like showed seen in evidence from found Mountains with similar features Puzzle Pieces On different continents Continental ice sheets
1. SHAPE OF THE CONTINENTS Continentft together lke puzzle pieces Madagascar AFRICA Sri Lanka INDIA SOUTH AMERICA AUSTRALIA ANTARCTICA Map O2007 Richard W. Hughes
2. FOSSIL EVIDENCE SAME FOSSILS: DIFFERENT CONTINENTS Lystrosaurus Africa AFRICA INDIA South America USTRALI SOUTH AMERICA ANTARTICA Cynognathus Glossopteris Mesosaurus Mesosaurus was incapable of swimming across a large ocean.
Geological Evidence SAME ROCK: DIFFERENT RANGE Existing mountain ranges separated by vast oceans contain rocks of identical mineral content. -A prime example are the Appalachian Mountains in the eastern U.S and the Caledonian Mountains in the British Isles. edonian Hercyn ercynian Front Triassic Cape Foldings
Criticism Forces -not sufficient to drift the continents Precarboniferous history not known Why only northward and westward drift Sial floating over Sima - in reality lithosphere is floating on aesthenosphere . Formation of mountains(rockies and Andes) due to friction by Sima is self contadictory Did not explain the formation of oceanic ridges and Island arcs
B Tech from MNIT, Jaipur. Appeared in CSE interview thrice. Loves teaching and playing badminton.