Product Code Database
A cuesta () 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 stratum, called caprock. Where erosion has exposed the frontslope of this, a steep slope or escarpment occurs. The resulting terrain may be called scarpland.
Cuestas, , 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.
The Gulf Coastal Plain in Texas is punctuated by a series of cuestas that parallel the coast, as are most coastal plains. 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 Cretaceous chalk White Horse Hills and the similarly aligned escarpment of the Jurassic limestones in the Cotswolds, 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 Surrey
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.
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.
|
|
