Escarpment

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Escarpment face of a cuesta, broken by a fault, overlooking Trenton, Cloudland Canyon State Park, and Lookout Mountain, in Georgia

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

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 (dip) slope on one side and a steep scarp slope 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[citation needed] caused by coastal erosion at the base of the plateau.

Formation and description[edit]

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[edit]

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[edit]

Africa[edit]

Antarctica[edit]

Asia[edit]

Australia and New Zealand[edit]

Europe[edit]

The Sierra Escarpment in California.

North America[edit]

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[edit]

See also[edit]

References[edit]

  1. ^ Easterbrook, D. J. (1999) Surface processes and landforms. (Second Ed). Prentice Hall, Upper Saddle River, New Jersey.
  2. ^ Summary: Escarpments, US Army Corps of Engineers.
  3. ^ Lidmar-Bergström (1988). "Denudation surfaces of a shield area in southern Sweden". Geografiska Annaler. 70 A (4): 337–350.