A fault is a break or fracture in the Earth's crust, caused by tectonic forces along which slippage of rock has occurred.
Sometimes the fractures may be very small (almost as thin as hair), with very slight movement between the rock layers. However, faults are known to run for hundreds of miles, such as the San Andreas Fault in California, and the Anatolian Fault in Turkey. Both these faults are visible from space.
Earthquakes tend to occur along fault lines that are about 375 miles deep. Below that depth rocks tend to be a lot warmer, therefore faults cannot generate enough friction to create earthquakes.
There are three kinds of faults. Each fault is caused due to the different forces pushing or pulling on the Earth’s crust, thereby causing rocks to slide up, down, or past each other. The three faults are listed below:
- Strike-slip faults
- Normal faults
- Reverse or thrust faults
Faults can sometimes affect coal seams. The following are some effects of faults on coal mining:
- Off-setting of the coal seams
- Weakening of roof and ribs
- Admission of water and gas into workings
- Introduction of clay and other impurities into the coal
- Creation of grades that is too steep for mining equipment to reach