Faults are an important part of geology, as they form along planes of weakness in rocks.  This allows Geologists to study the stresses involved in the formation of these faults and thus infer the processes that formed the fault. Faults are fractures in a rock with movement along them due to tectonic pressures. Movement along these faults is the cause of most earth quakes. There are two types of faults, strike-slip and dip-slip.

Strike Slip Faults: this is where the fault plane within the rock is near vertical at around 90° from the horizontal surface. There are two types of these faults, left-lateral and right-lateral.

• Left-lateral Strike Slip Faults: when you stand on one side of the fault and look towards the other, the other side has appeared to move to left.
• Right-lateral Strike Slip Fault: when you stand on one side of the fault and look towards the other, the other side has appeared to move to right.

Dip-slip Faults: This type of fault is associated with either extension of earth’s crust or compression of it. There are two types of dip-slip faults, normal and reverse. With normal faults forming at ~60° from horizontal and reverse faults forming at ~30° from horizontal.

• Normal Fault:  Normal faults occur when the crust of the earth is extended, causing the two rock walls to move farther apart from one another to accommodate for extension.

• Reverse Fault: Reverse faults occur when the crust of the earth is compressed, causing the two rock walls to move closer together to accommodate for the pressure.

This video explains faults, where they form and why they form in a easy to understand fashion.

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