- Fault scarp
A fault scarp is the topographic expression of faulting attributed to the displacement of the land surface by movement along the fault. It can be caused by differential
erosion along an old "inactive"geologic fault (a sort of old rupture) with hard & weak rock, or by a movement on an active fault. In many cases, bluffs form from the upthrown block and can be very steep. The height of the scarp formation is equal to the vertical displacement along the fault. Active scarps are usually formed bytectonic displacement, e.g. when anearthquake changes the elevation of the ground, and can be caused by any type of fault, includingstrike-slip fault s, whose motion is primarily horizontal. This movement is usually episodic, with the height of the bluffs being the result of multiple movements over time. Displacement of around 5 to 10 meters per tectonic event is common.Fact|date=December 2007Due to the dramatic uplift along the fault, the fault scarp is very prone to erosion, especially if the material being uplifted consists of unconsolidated sediment. Weathering, mass wasting and water runoff can soon wear down these bluffs. Fault scarps may be only a few centimeters or many meters high. "Fault-line scarps" are coincident with faults, but are most typically formed by the erosion of weaker rocks that have been brought alongside more resistant ones by the movement along the fault. In the case of old eroded fault scarps, active erosion may have moved the physical
cliff back away from the actual fault location which may be buried beneath atalus ,alluvial fan or the valley fill.Notable characteristics
The rapid erosion of these bluffs can create defined V-shaped valleys along runoff channels. Adjacent V-shaped valley formations give the remaining fault spurs a very triangular shape. This formation is known as a "triangular facet"; however, this landform is not limited to fault scarps.
Examples
The
Teton Range inWyoming is an example of an active fault scarp. The dramatic topoography of the Tetons is due to the geologically recent activity on the Teton fault.Fact|date=April 2008 TheHurricane Cliffs , west ofZion National Park inUtah is a prominent example of a fault scarp along an old essentially inactive fault. Other examples include the scarps bounding the East African Rift Valley and theRio Grande Rift inNew Mexico .In other parts of the world, many fault
scarp s exist in the Eastern and WesternAlps . InNew Zealand a large scarp can be seen at Maruia Falls on theShenandoah Highway ,South Island . The 1929 Murchison Earthquake raised the upstream side by about four metres thereby creating a fault scarp and as a result also, awaterfall .References
Easterbrook, D. J. (1999) "Surface processes and landforms." (Second Ed). Prentice Hall, Upper Saddle River, New Jersey.
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