Thrust fault
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A thrust fault is a particular type of fault, or break in the fabric of the Earth's crust with resulting movement of each side against the other, in which one side is pushed up relative to the other and somewhat over it. This is the result of compressional forces. A normal fault is similar but results from tension or extensional forces with the upper side dropping down relative to the lower. Differential erosion across the fault trace can result in a cliff on the fault scarp. Another name for high angle thrust fault is reverse fault. If the angle of the fault plane is low (generally less than 20 degrees from the horizontal) and the displacement of the overlying block is large (often in the kilometer range) the fault is called an overthrust.
Large overthrust faults occur in areas that have undergone great compressional forces. These conditions exist in the orogenic belts that result when two continental tectonic plates collide. The resultant compressional forces produce mountain ranges. The Himalayas, the Alps, and the Appalachians are prominent examples of compressional orogenies with numerous overthrust faults.