Isostasy YouTube Lecture Handouts

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Story of Isostasy and 7 Theories of Isostasy - Fundamentals of Geography

ISOSTASY

Concept of isostasy, story of origin of isostasy and theories of isostasy are explained in this video by Dr. Manishika Jain. The various theories explained are: 1. Airy՚s model2. Pratt՚s Model3. Heikesenen՚s Model4. Hayford and Bowie՚s Model - level of compensation5. Joly՚s Model6. Holmes and Holmes Model7. Dutton՚s Model

Illustration: ISOSTASY

Then What is ISOSTASY?

Illustration: Then What is ISOSTASY?

Story of Isostasy! !

Bouguer Correction

Deflection of Vertical in India

Illustration: Story of Isostasy! !

Airy՚s Theory

Varying crustal thickness laterally

Illustration: Airy՚s Theory

CRITICS of AIRY՚s THEORY

  • Assumption of thin crust
  • Crust was less dense than underlying – lava
  • Not in accordance to contraction theory of earth

DEPTH of COMPENSATION

Illustration: DEPTH of COMPENSATION

Pratt՚s Theory

Varying Crustal Density Laterally

Illustration: Varying Crustal Density Laterally

Vertical Movement of Land

Illustration: Vertical Movement of Land

Dutton՚s Theory

Coined term “ISOSTASY”

Equal masses must underlie equal surface areas

Elevated mass ⇾ Low Density

Depressed mass ⇾ High Density

Heiskenen՚s Theory

AIRY + PRATT

Higher density ⇾ Shorter Columns

Hayford and Bowie Theory

Similar to Pratt

Inverse relation between height of column and density

Joly՚s Theory

Contradicted Hayford and Bowie

Zone of Compensation (10-mile thick)

Holmes & Holmes Theory

Supported Airy

High columns can stand - Have lighter material below them for greater depth

Equal weight along level of equal pressure

Illustration: Holmes & Holmes Theory

Manishika