A cuesta (from

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Can ...

''cuesta'' "slope") is a

hill A hill is a landform that extends above the surrounding terrain. It often has a distinct Summit (topography), summit. Terminology The distinction between a hill and a mountain is unclear and largely subjective, but a hill is universally con ...

ridge A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The line ...

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 A dip slope is a topographic (geomorphic) surface which slopes in the same direction, and often by the same amount, as the true dip or apparent dip of the underlying strata.Jackson, JA, J Mehl and K Neuendorf (2005) ''Glossary of Geology.'' Amer ...

that conforms with the dip of resistant

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

, called

caprock Caprock or cap rock is a more resistant rock type overlying a less resistant rock type,Kearey, Philip (2001). ''Dictionary of Geology'', 2nd ed., Penguin Reference, London, New York, etc., p. 41.. . analogous to an upper crust on a cake that is har ...

. Where erosion has exposed the frontslope of this, a steep slope or

escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. The terms ''scarp'' and ''scarp face'' are often used interchangeably with ''escar ...

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

: "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.Cotton, CA (1952) ''Geomorphology An Introduction to the Study of Landforms.'' John Wiley and Sons, New York. 505 pp.Simonett, SD (1968) ''Cuesta.'' In RW Fairbridge, ed., pp. 233, ''The Encyclopedia of Geomorphology'' (Encyclopedia of Earth Sciences, Volume III), Reinhold, New York, 1296 pp. Jackson, JA, J Mehl and K Neuendorf (2005) ''Glossary of Geology.'' American Geological Institute, Alexandria, Virginia. 800 pp.

Formation

Cuestas are the expression of extensive outcrops of gently dipping strata, typically

sedimentary Sedimentary rocks are types of rock (geology), rock that are formed by the accumulation or deposition of mineral or organic matter, organic particles at Earth#Surface, Earth's surface, followed by cementation (geology), cementation. Sedimentati ...

strata, that consist of alternating beds of weak or loosely cemented strata, i.e.

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from '' shale'' by its lack of fissility (parallel layering).Blatt, H., and R.J. Tracy, 1996, ''Petrology. ...

, and

marl Marl is an earthy material rich in carbonate minerals, clays, and silt. When hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae. Marl makes up the lower part o ...

and hard, well-lithified strata, i.e.

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

and

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

. The surfaces of the hard, erosion-resistant rock strata form the caprock of the backslope (dip-slope) of the cuesta, where erosion has preferentially removed the weaker strata. The frontslope of the cuesta consists of an escarpment that cuts across the

bedding Bedding, also known as bedclothes or bed linen, is the materials laid above the mattress of a bed for hygiene, warmth, protection of the mattress, and decorative effect. Bedding is the removable and washable portion of a human sleeping environm ...

of the strata comprising it. Because of the gently dipping nature of the strata that forms a cuesta, a significant shift in horizontal location will take place as the landscape is lowered by

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

. Because the slope of a cuesta dips in the same direction as the sedimentary strata, the dip angle of this bedding (θ) can be calculated by (''v'' / ''h'') = tan(θ) where ''v'' is equal to the vertical distance and ''h'' is equal to the horizontal distance perpendicular to the strike of the beds. Cuestas,

homoclinal ridge A homoclinal ridge or strike ridge is a hill or ridge with a moderate, generally between 10° to 30°, sloping backslope. Its backslope is a ''dip slope,'' that conforms with the dip of a resistant stratum or strata, called ''caprock.'' On the oth ...

s, 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.

Examples

Two well-known cuestas in western New York and southern

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

are the

Onondaga escarpment The Onondaga Limestone is a group of hard limestones and dolomites of Devonian age that form an important geographic feature in some areas in which it outcrops; in others, especially its Southern Ontario portion, the formation can be less promi ...

and the

Niagara Escarpment The Niagara Escarpment is a long escarpment, or cuesta, in Canada and the United States that runs predominantly east–west from New York through Ontario, Michigan, Wisconsin, and into Illinois. The escarpment is most famous as the cliff over ...

, respectively. The dip of the Onondaga is about 40 feet per mile (about 7.6 m/km) to the south. The escarpment edge faces north, and in its most populated section, runs roughly parallel to the southern

Lake Ontario Lake Ontario is one of the five Great Lakes of North America. It is bounded on the north, west, and southwest by the Canadian province of Ontario, and on the south and east by the U.S. state of New York. The Canada–United States border sp ...

shoreline. The

Gulf Coastal Plain The Gulf Coastal Plain extends around the Gulf of Mexico in the Southern United States and eastern Mexico. This coastal plain reaches from the Florida Panhandle, southwest Georgia, the southern two-thirds of Alabama, over most of Mississippi, wes ...

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

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 The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

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 The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk ...

White Horse Hills The Berkshire Downs are a range of chalk downland hills in South east England split between the counties of Berkshire and Oxfordshire. They are part of the North Wessex Downs Area of Outstanding Natural Beauty. The western parts of the downs ...

and the similarly aligned escarpment of the

Jurassic The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The J ...

limestones in the

Cotswolds The Cotswolds (, ) is a region in central-southwest England, along a range of rolling hills that rise from the meadows of the upper Thames to an escarpment above the Severn Valley and Evesham Vale. The area is defined by the bedrock of Jur ...

, sometimes called the Cotswold Edge. In continental Europe, the Swabian Alb offers particularly good views of cuestas in

rock. In

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

, 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 Côte is a British cafe chain founded by Richard Caring, Andy Bassadone, Chris Benians and Nick Fiddler in Wimbledon, London Wimbledon () is a district and town of Southwest London, England, southwest of the centre of London at Charing Cross ...

. The Machinchang Formation outcrops in the

Langkawi Langkawi, officially known by its sobriquet Langkawi, the Jewel of Kedah ( ms, Langkawi Permata Kedah ), is a duty-free island and an archipelago of 99 islands (plus five small islands visible only at low tide in the Strait of Malacca) loc ...

islands off the coast of northwestern

Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federation, federal constitutional monarchy consists of States and federal territories of Malaysia, thirteen states and three federal territories, separated by the South China Sea into two r ...

. The formation is one of the oldest exposed rock units in Southeast Asia and has an extensive eroded

anticline In structural geology, an anticline is a type of fold that is an arch-like shape and has its oldest beds at its core, whereas a syncline is the inverse of an anticline. A typical anticline is convex up in which the hinge or crest is the ...

cuesta topography—dating back to Cambrian.

References

External links

{{Commons category, Cuestas
Escarpment geology
Geomorphology Structural geology Slope landforms Erosion landforms Ridges

Definition

Formation

Examples

See also

References

External links