escarpment

Escarpment face of a cuesta, broken by a fault. Cumberland Plateau, Tennessee.

In geomorphology, an escarpment is a transition zone between different physiogeographic provinces that involves a sharp, steep elevation differential, characterized by a cliff or steep slope.

Description and variants

Usually escarpment is used interchangeably with scarp (from the Italian scarpa, shoe^[1]). But some sources differentiate the two terms, where escarpment refers to the margin between two landforms, while scarp is synonymous with a cliff or steep slope.^[2][3] The surface of the steep slope is called a scarp face. Scarps are generally formed by one of two processes: either by differential erosion of sedimentary rocks, or by vertical movement of the Earth's crust along a fault (faulting).

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

Most commonly, an escarpment is a transition from one series of sedimentary rocks to another series of a different age and composition. When sedimentary beds are tilted and exposed to the surface, erosion and weathering may occur differentially based on the composition. Less resistant rocks will erode faster, retreating until the point they are overlain by more resistant rock (see cross section schematic). When the dip of the bedding is gentle, a cuesta is formed. Steeper dips (greater than 30-40°)^[2] form hogbacks.

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.

More loosely, the term scarp describes the zone between coastal lowlands and continental plateaus which have a marked, abrupt change in elevation caused by coastal erosion at the base of the plateau.

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 (i.e. enhanced) 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 vast chain of hills squeezed between the fault and the mountains of New Zealand's Southern Alps. Northeast is towards the top.

Significant escarpments

Africa

• Elgeyo escarpment (Great Rift Valley)
• God's Window (South Africa)
• Great Escarpment (South Africa)
• Bandiagara Escarpment (Mali)
• Zambezi Escarpment (Zambia)
• Scarp of Angola (Angola)

Antarctica

• Usas Escarpment

Asia

• Vindhyan Escarpment (India)

Australia and New Zealand

• Australia
  • Darling Scarp
  • Dorrigo Plateau
  • Illawarra Escarpment
  • Nullarbor Escarpment
• New Zealand
  • The western slope of the Southern Alps (along the Alpine Fault)
  • The Kaimai escarpment, above the Hauraki Plains

Europe

• England
  • Cotswold escarpment
  • North Downs
  • South Downs
  • A colloquial adjective to describe escarpments in England is "edge" as in
    • Alderley Edge
    • Edge Hill famous as the place of the first battle of the English Civil War.
    • Kinver Edge
    • The Lincoln Edge
    • Wenlock Edge
• France
  • La Côte d'Or is famous for its wines and has given its name to a département, Côte-d'Or.
  • Le Pays de Bray, a clay vale enclosed by chalk escarpments.
• Germany
  • Swabian Alb
• Sweden, Estonia and Russia
  • Baltic Klint
  • Gotland–Saaremaa Klint
• Malta
  • Victoria Lines

The Sierra Escarpment in California.

North America

• Canada and the United States
  • Niagara Escarpment (Ontario, Illinois, Michigan, New York, and Wisconsin)
  • Onondaga (geological formation) (Ontario and New York)
  • Devil's Rock (Lake Temiskaming, Ontario)
• United States
  • Allegheny Front (Pennsylvania-Maryland-West Virginia)
  • Balcones Fault (Texas)
  • Blue Ridge Escarpment (South Carolina-Georgia)
  • Caprock Escarpment (Texas)
  • Catskill Escarpment (New York)
  • Cody Scarp (Florida)
  • Elkhorn Scarp (San Andreas Fault)
  • Highland Rim encircling the Nashville Basin (actually a geologic dome) in Middle Tennessee
  • Knobstone Escarpment (Southern Indiana)
  • Mescalero Escarpment (New Mexico)
  • Missouri Escarpment (North Dakota)
  • Mogollon Rim (Arizona)
  • Muldraugh Hill (Kentucky)
  • Nickel Escarpment, formally Sigsbee Escarpment, Gulf of Mexico
  • Pine Ridge (Nebraska and South Dakota)
  • Pottsville Escarpment (Kentucky-Tennessee; see Cumberland Plateau)
  • Sierra Nevada range (eastern slope) in California
  • Portage Escarpment (Ohio)

See also

• Cuesta
• Fall line
• List of scarps on Mercury

References

1. ^ scarp - Definition from the Merriam-Webster Online Dictionary
2. ^ ^{a b} Easterbrook, D. J. (1999) Surface processes and landforms. (Second Ed). Prentice Hall, Upper Saddle River, New Jersey.
3. ^ Summary: Escarpments, US Army Corps of Engineers.