Earthquakes

• The shaking of the Earth’s crust caused by a release of energy.

• The major cause is the build up of stress between two lithospheric plates.

• Sometimes plates moving past each other will lock, and over time stress builds. Plates begin to change shape and deform as well.

• Eventually, the stress becomes too much and the plate slips. This movement is what causes the earthquake.

• The plates that had become deformed snap back into their original shape. (This process is known as the Elastic Rebound Theory).

Folding and Faulting

• When lithospheric plates are put under stress, they react by folding or faulting.

• A fold occurs due to compressional stress or plates moving towards each other.

• 2 Basic Folds:

• Anticline• Syncline

• A fault is a crack or break in the Earth’s crust where movement has occurred.

• 3 Basic faults :

• Normal• Reverse• Strike-slip

• Anticline- An upwards fold.

• Syncline- A downward fold.

• Normal Fault- caused by tensional stress (crust is being pulled apart) and one rock plane drops down on one side of the fault.

• Reverse Fault- caused by compression stress (crust is being pushed together) and one rock plane rides up on one side of the fault.

• Strike-slip- caused by shear stress and the rocks on either side moved horizontally past each other.