EXPLORATION: Layers and Plate Tectonics

If rock is stressed enough, a fault may occur. A fault is simply a crack in the earth's crust. Faults can occur in the middle of a plate or at a plate boundary. The crust moves either vertically, horizontally or a combination of both (obliquely) on each side of the fault.

Fault types:

Normal Fault
In a normal fault, one section rises up and over in comparison to the other, resulting in the hanging wall overhanging the foot wall.

Reverse Fault
In a a reverse fault, one section drops down with no overhanging.
Slip-strike fault
In a slip strike fault, the sections are sliding past each other.

Diagram of a slip-strike fault (from above)

The San Andreas fault in California is a famous example of a slip-strike fault

Note it is not usually this simple. There can be a mixture of horizontal and vertical movement in a fault. For example a horizontal tear fault may occur with a reverse fault.
As well, there are often many faults occurring together, which geographers call a "fault zone."

Horsts and Grabens

These fault types result in large blocks of crust either being raised up or sunk down. This often forms mountain ranges.

Diagram of Horst and Graben

The Grand Teton Range of the Rock Mountains in Wyoming are an example of Horst or Fault Block Mountains