Structures In Rocks Topics

Geologic Structures (Part 4)

Strike-slip Faults

• If rock blocks slide past each other in a horizontal direction, the fault is called a strike-slip fault.  Strike-slip faults are caused by lateral shear stress.

Strike-slip FaultStrike-slip fault (Diagram by Phyllis Newbill)

Strike-slip field photoStrike-slip fault in the field (Photograph by Stan Johnson)

The above photograph shows a strike-slip fault in Virginia.

Environmental Effects of Faulting

• Faults are important because, like joints, they create surfaces along which fluids (such as oil or water) can travel.

Groundwater on fault
Groundwater along a fault (Photograph by Rober Whisonant)

MapFaults are important for groundwater storage and movement.  The photograph above shows how groundwater has moved through rocks along a fault.  Iron stains on the rock indicate that water has flowed out of this fault exposure.  This picture was taken in Tazewell County.       

• Faults can also provide potential surfaces along which rocks can slide.

• If faults move suddenly, they generate earthquakes.

Rock slide
Rock slide along a fault (Photograph by Robert Whisonant)

MapThe photograph above shows a huge rock block sticking out of a road cut because the block has slid along a fault plane.  This cut is near Bluefield.