Here's why:

* Fault: A fracture in the Earth's crust where there has been movement.

* Slip: The amount of movement that has occurred along the fault.

* Differential: Meaning "different" or "varying."

Differential slip occurs when the movement (slip) on opposite sides of a fault is not equal in either direction or rate. This can lead to a variety of geological features, such as:

* Offsetting layers: Rocks on one side of the fault may be shifted horizontally or vertically compared to the other side.

* Folding: The pressure from differential slip can cause rocks to fold and bend.

* Strain: The rocks on either side of the fault experience different amounts of stress, which can lead to strain (deformation).

Let me know if you have any other questions!