Mountain Building Theories Part 2 Youtube Lecture Handouts

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Watch video lecture on YouTube: 2 Major Theories in Mountain Building - Geosynclinal Orogen & Plate Tectonic Theory

2 Major Theories in Mountain Building - Geosynclinal Orogen & Plate Tectonic Theory

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19th century: Everest, Pratt, and Airy- gravity anomalies

Observations

  • Sedimentary rock layers folded and crumpled.

  • Folding exists even where no mountains

  • Distribution of folding belts varies from continent to continent.

    • North America, oldest on the interior

    • Asia, youngest on the interior

    • Europe, oldest to the North.

Conclusions

  • Mountains formed due to compressional force.

  • Compressional force acts parallel to surface of the Earth.

  • Compressional forces vary with time and space.

Thermal Contraction Theory of Mountain Building by Jeffreys

  • Shortening of Crust (Thinning) – Lateral

  • Level of No Strain

  • Ocean Cooling is More

  • N-S Rocks Explained

Radioactive Theory of Mountain Building of Joly

Retention of heat below SIMA due to radioactivity and lack of thermal gradient b/w SIMA and SIAL

Melting -> Expansion,

  • Melting of Substratum -> Max Expansion – Transgressional Sea

  • Resolidification of Substratum -> Max Contraction – Regressional Sea

    Radioactive Theory of Mountain Building of Joly

    Radioactive Theory of Mountain Building of Joly

    Radioactive Theory of Mountain Building of Joly

Thermal Convection Currents by Arthur Holmes

Thermal Convection Currents by Arthur Holmes

Thermal Convection Currents by Arthur Holmes

Thermal Convection Currents by Arthur Holmes

Du Toit

  • South African geologist Alexander Du Toit

  • Remarkable similarities between the geology of South Africa and South America.

  • Both continents, as well as India and Australia were all home to the same species of fossil plant.

  • All four continents had glacial striations

  • South America glaciers moving onto land from the ocean.

  • Postulated that all four of these continents were once united

  • Gondwanaland.

  • Alfred Wegener gave the Continental Drift Theory.

Continental Drift Theory of Mountain Building by Alfred Wegner

Continent Sliding Hypothesis of Mountain Building of Daly

Continent Sliding Hypothesis Image-1

Continent Sliding Hypothesis Image-1

Continent Sliding Hypothesis Image-1

Continent Sliding Hypothesis Image-2

Continent Sliding Hypothesis Image-2

Continent Sliding Hypothesis Image-2

Continental Drift: