Cuesta

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Escarpment face of a cuesta broken by a fault.Lookout Mountain Georgia.
Escarpment face of a cuesta broken by a fault.
Lookout Mountain Georgia.
Schematic cross section of three cuestas, dipslopes facing left, and harder rocklayers in darker colors than softer ones
Schematic cross section of three cuestas, dipslopes facing left, and harder rocklayers in darker colors than softer ones

In structural geology and geomorphology, a cuesta (from Spanish: "slope") is a ridge formed by gently tilted sedimentary rock strata in a homoclinal structure[1][2]. Cuestas have a steep slope, where the rock layers are exposed on their edges, called an escarpment or, if more steep, a cliff. Usually an erosion-resistant rock layer also has a more gentle slope on the other side of the ridge called a 'dip slope'.

Two well-known cuestas in western New York and southern Ontario are the Onondaga escarpment and the Niagara escarpment. The dip of the Onondaga is about 40 feet per mile to the south. The escarpment edge faces north and, in its most populated section, runs roughly parallel to the southern Lake Ontario shoreline.

Most Coastal Plains around the world are punctuated by a series of cuestas that parallel the coast.[3] The cuestas have gentle slopes over resistant strata at the surface and steeper slopes where these resistant strata are cut. That means that steeper slopes face inside anticlinals and outside eroded sinclinals. The Reynosa Plateau is the most coast-ward cuesta, which sees surface expression with the Bordes-Oakville escarpment, on the northwest side and a low ridge on the eastern boundary, called the Reynosa cuesta, where the deposits dip below later Pliocene-Pleistocene deposits of the Willis and Lissie Formation.

Cuestas have less dramatic expression in the United Kingdom, with two notable examples being the northwest-facing escarpment of the Jurassic chalk White Horse Hills and the similarly-aligned escarpment of the Cotswolds. In continental Europe, the Swabian Alb offers particularly good views of cuestas in Jurassic rock. In France, the term for a cuesta is the same as for a coastline: "côte". Notable French cuestas are the wine-growing regions of Côte d'Or and Côtes du Rhône.

[edit] References

  1. ^ Monkhouse, F. J. A Dictionary of Geography. London: Edward Arnold, 1978
  2. ^ Cuesta, or homoclinal ridge (geology). Britannica Online Encyclopedia. Retrieved on 2008-03-16. “Cuestas with dip slopes of 40°–45° or higher are usually called hogback ridges.”
  3. ^ Strahler, Arthur N. Physical Geography. New York: John Wiley & Sons, Inc, 1960 (second edition), p. 450

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