Isostasy YouTube Lecture Handouts

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


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 model 2. Pratt՚s Model 3. Heikesenen՚s Model 4. Hayford and Bowie՚s Model - level of compensation 5. Joly՚s Model 6. Holmes and Holmes Model 7. Dutton՚s Model

Isostacy is Not Force or Process

Then What is ISOSTASY?

Balance of Isostacy

Story of Isostasy! !

Bouguer Correction

Deflection of Vertical in India

Density and Isostacy

Airy՚s Theory

Varying crustal thickness laterally

Demonstrating 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 in Isostacy

Pratt՚s Theory

Varying Crustal Density Laterally

Pratts Theory of Varying Density Blocks

Vertical Movement of Land

Vertical Movement of Land: Forces in Lithosphere and Astheno …

Dutton՚s Theory

Coined term “ISOSTASY”

Equal masses must underlie equal surface areas

Elevated mass ⇾ Low Density

Depressed mass ⇾ High Density

Heiskenen՚s Theory


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

Holmes Theory with Isostacy in Different Landforms