Structures In Rocks Topics

Geologic Structures (Part 3)

Reverse Faults

• If the hanging wall moves up relative to the footwall, the fault is a reverse fault.  Reverse faults are caused by compressional stress, or stress that pushes rocks together.

Reverse Fault
Reverse fault. Note that the right side of the fault is the hanging wall which has moved up relative to the left side. (Diagram by Phyllis Newbill)

Reverse FaultReverse fault (Photograph by Stan Johnson)

MapThis reverse fault is in Giles County.  The gray limestone in the hanging wall block has moved up relative to the shale rocks of the footwall.



Thrust Faults

• If the angle of the reverse fault is low (<15°), the fault is called a thrust fault.

Thrust FaultThrust fault (Diagram by Phyllis Newbill)

A thrust fault is a special type of reverse fault because it has a low angle.  Thrust faults are also the result of extreme compressional stress, such as occurs when tectonic plates come together to form mountains.

Thrust faultThrust fault (Photograph by Robert Whisonant)

Map This Scott County thrust fault has Cambrian limestone pushed over Mississippian shale.  Look for the fault just below the arrow.  Thrust faults are caused by horizontal compression.

360 to 320 million years ago
570 to 505 million years ago