Types of stress that influence rock behaviours, continental drift theory and plate tectonics

Geological stress

is the force (from the pushing and pulling of plates) that acts on the rocks thereby creating different behavior or characteristics.

Confining stress

the crust becomes compact, making it look smaller

Compressional stress

rocks push or squeeze against one another. The stress produced is directed toward the center.

Tensional stress

rocks are pulled apart.

Shear stress

some of the portions of a plate at the edges may break away in different directions, eventually making the plate smaller in size.

Alfred Wegener - 1912

when and who developed the concept and hypothesized the continental drift theory

there used to be only one supergiant landmass (Pangea) where all the continents came from.

What did Wegener A. claim

continental drift hypothesis

refers to the theory where at one point in time, all of the continents were joined together in one large landmass prior to splitting apart and drifting into their current positions (known as the various continents in the world today).

Plate tectonic theory

explanation of the moving continents

Arthur Holmes, 1929

when and who suggested thermal convection as the driving force of the movement of the continents

When a substance is heated, its density decreases and rises to the surface until its cooled and then sinks again. the repeating process of heating and cooling may produce a current that is strong enough to make continents move.

Explain the concept of thermal convection

1. Pacific plate

2. Indian plate

3. Eurasian plate

4. North American plate

5. South American plate

6. Indo-Australian plate

7. Antarctic plate

8. African plate

What are the 8 major plates?

Boudaries

areas where the highest hazards are. This is where the plates have the highest tension and therefore are exit points for energy release.

Convergent boundaries

This is a boundary where plates meet.

Divergent boundaries

The boundary where plates move away from each other.

Transform Boundaries

where the plates slide past each other and neither plate gets subducted.