Cuesta
A cuesta (from Spanish cuesta "slope") is a hill or ridge with a gentle slope on one side, and a steep slope on the other. In geology the term is more specifically applied to a ridge where a harder sedimentary rock overlies a softer layer, the whole being tilted somewhat from the horizontal. This results in a long and gentle backslope called a dip slope that conforms with the dip of resistant strata, called caprock. Where erosion has exposed the frontslope of this, a steep slope or escarpment occurs. The resulting terrain may be called scarpland.
Definition
In general usage, a cuesta is a hill or ridge with a gentle slope (backslope) on one side, and a steep slope (frontslope) on the other. The word is from Spanish: "flank or slope of a hill; hill, mount, sloping ground". In geology and geomorphology, cuesta refers specifically to an asymmetric ridge with a long and gentle backslope called a dip slope that conforms with the dip of a resistant stratum or strata, called caprock. The outcrop of the caprock forms a steeper or even cliff-like frontslope (escarpment), cutting through the dipping strata that comprise the cuesta.[1][2][3]
Formation
Cuestas are the expression of extensive outcrops of gently dipping strata, typically
Cuestas, homoclinal ridges, and hogbacks comprise a sequence of landforms that form a gradational continuum. These landforms differ only on the steepness of their backslopes and the relative differences in the inclination of their backslopes and frontslopes. These differences depend upon whether the dip of the strata from which they have been eroded are either nearly vertical, moderately dipping, or gently dipping. Because of their gradational nature, the exact angle of the backslope that separates these landforms is arbitrary and some differences in the specific angles used to define these landforms occur in the scientific literature. It also can be difficult to sharply distinguish immediately adjacent members of this series of landforms because of their gradational nature.[2][4][5][7]
Examples
Two well-known cuestas in western
The Gulf Coastal Plain in Texas is punctuated by a series of cuestas that parallel the coast, as are most coastal plains.[8] The Reynosa Plateau is the most coast-ward cuesta, which has 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 Formations.
Cuestas have less dramatic expression in the United Kingdom, with two notable examples being the northwest-facing escarpment of the
, sometimes called the Cotswold Edge. Other examples include the Brecon Beacons, Wenlock Edge, the Chilterns, the North and South Downs and the Greensand Ridge of Kent and SurreyIn continental Europe, the
The Machinchang Formation outcrops in the Langkawi islands off the coast of northwestern Malaysia. The formation is one of the oldest exposed rock units in Southeast Asia and has an extensive eroded anticline cuesta topography—dating back to Cambrian.[citation needed]
See also
- Flatiron (geomorphology) – Steeply sloping triangular landform
References
- ^ a b Cotton, CA (1952) Geomorphology An Introduction to the Study of Landforms. John Wiley and Sons, New York. 505 pp.
- ^ ISBN 978-0879331795
- ISBN 0-922152-76-4
- ^ a b Thornbury, W. D. (1954). Principles of Geomorphology. New York: John Wiley & Sons.
- ^ ISBN 1-875553-02-9.
- ISBN 0-13-860958-6.
- ISBN 0-87933-179-8.
- ^ Strahler, A. N. (1960). Physical Geography (2nd ed.). New York: John Wiley & Sons.