CONTINENTAL DRIFT AND PLATE TECTONICS

Contents

1. Supercontinent 32

1.1. Supercontinent Cycle 32

1.2. Pangaea 33

2. Continental Drift 33

2.1. Continental Drift Theory of Alfred Wegener.........................................................................

2.1.1. Evidences in Support of the Theory 34

2.1.2. Forces for Drifting 35

2.1.3. Criticism of Wegener’s Theory 35

3. Post-Drift Studies 35

3.1. Convection Current Theory 36

3.2. Mapping of Ocean Floor 36

3.3. Sea Floor Spreading 36

4. Plate Tectonics 37

4.1. Major and Minor Plates 37

4.2. Movement of Plates 38

4.2.1. Movement of The Indian Plate 39

4.3. Types of Boundaries 39

4.3.1. Divergent Boundaries 40

4.3.2. Convergent Boundaries 40

4.3.3. Transform Boundaries 40

4.4. Forces for the Plate Movement 40

4.5. Objections to Plate Tectonics Theory 40

5. Endogenic and Exogenic Forces 41

5.1. Geomorphic Processes and Agents 41

5.2. Endogenic Processes 41

5.2.1. Diastrophism 41

5.2.2. Volcanism 42

5.3. Exogenic Processes 42

5.3.1. Weathering 43

5.3.2. Mass Movement 45

5.3.3. Erosion and Deposition 46

EARTH OF THE DISTANT PAST WAS A VERY DIFFERENT PLANET THAN THE ONE WE KNOW TODAY

1. Supercontinent

If you could travel through time to arrive at the Earth of a billion years ago, you would have a hard time navigating. A strange giant continent and a single planetary ocean would replace the familiar continents and oceans of today’s world. A supercontinent is the assembly of most or all the Earth’s continental blocks to form a single large landmass. There is no unanimity among tectonicists on a single definition of supercontinent. Hoffman (1999) used the term “supercontinent” to mean “a clustering of nearly all continents”. According to this definition, Pangaea is a supercontinent while Gondwana is not. There are other scholars who consider Gondwanaland a supercontinent of pre-Cambrian period.

In the past, there existed many supercontinents at different time. The positions of continents have been accurately determined back to the early Jurassic period. However, beyond 200 million years, continental positions are much less certain. Following is the list of supercontinents.