Escarpment

An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. Usually scarp and scarp face are used interchangeably with escarpment.

Escarpment face of a cuesta, broken by a fault, overlooking Trenton, Cloudland Canyon State Park, and Lookout Mountain, in Georgia (USA)

Some sources differentiate the two terms, however, where escarpment refers to the margin between two landforms (while scarp remains synonymous with a cliff or steep slope).[1][2] In this usage an escarpment is a ridge which has a gentle slope on one side and a steep scarp on the other side.

More loosely, the term scarp also describes a zone between a coastal lowland and a continental plateau which shows a marked, abrupt change in elevation[3] caused by coastal erosion at the base of the plateau.

Formation and description

Scarps are generally formed by one of two processes: either by differential erosion of sedimentary rocks, or by movement of the Earth's crust at a geologic fault. The first is the more common type: the escarpment is a transition from one series of sedimentary rocks to another series of a different age and composition. Escarpments are also frequently formed by faults. When a fault displaces the ground surface so that one side is higher than the other, a fault scarp is created. This can occur in dip-slip faults, or when a strike-slip fault brings a piece of high ground adjacent to an area of lower ground.

Schematic cross section of a cuesta, dip slopes facing left, and harder rocklayers in darker colors than softer ones

Earth is not the only planet where escarpments occur. They are believed to occur on other planets when the crust contracts, as a result of cooling. On other Solar System bodies such as Mercury, Mars, and the Moon, the Latin term rupes is used for an escarpment.

Shaded and colored image from the Shuttle Radar Topography Mission—shows an elevation model of New Zealand's Alpine Fault running about 500 km (300 mi) long. The escarpment is flanked by a chain of hills squeezed between the fault and the mountains of New Zealand's Southern Alps. Northeast is towards the top.

Erosion

When sedimentary beds are tilted and exposed to the surface, erosion and weathering may occur. Escarpments erode gradually and over geological time. The mélange tendencies of escarpments results in varying contacts between a multitude of rock types. These different rock types weather at different speeds, according to Goldich dissolution series so different stages of deformation can often be seen in the layers where the escarpments have been exposed to the elements.

Significant escarpments

Africa

Antarctica

Asia

Australia and New Zealand

Europe
The Sierra Escarpment in California

North America
At the Florida Escarpment, seen in the eastern Gulf of Mexico, the sea bed drops precipitously from less than 300 to 3,000 m (1,000 to 10,000 ft) over a short distance.

South America

See also

References
  1. Easterbrook, Don J. (1999). Surface Processes and Landforms. Prentice Hall. ISBN 978-0-13-860958-0.
  2. Summary: Escarpments, US Army Corps of Engineers.
  3. "Scarps and Terraces". Physiography. Radford University. Retrieved 24 December 2020.
  4. Lidmar-Bergström, Karna (1988). "Denudation surfaces of a shield area in southern Sweden". Geografiska Annaler. 70 A (4): 337–350. doi:10.2307/521267. JSTOR 521267.
  5. Wörner, Gerhard; Uhlig, Dieter; Kohler, Ingrid; Seyfried, Hartmut (15 February 2002). "Evolution of the West Andean Escarpment at 18°S (N. Chile) during the last 25 Ma: uplift, erosion and collapse through time". Tectonophysics. 345 (1): 183–198. doi:10.1016/S0040-1951(01)00212-8.
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