Escarpment

Last updated
Escarpment face of a cuesta, broken by a fault, overlooking Trenton, Cloudland Canyon State Park, and Lookout Mountain, in Georgia (USA) Cuesta - Lookout Mountain, Georgia.png
Escarpment face of a cuesta, broken by a fault, overlooking Trenton, Cloudland Canyon State Park, and Lookout Mountain, in Georgia (USA)

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.

Contents

The terms scarp and scarp face are often used interchangeably with escarpment.[ citation needed ] Some sources differentiate the two terms, with escarpment referring to the margin between two landforms, and scarp referring to a cliff or a steep slope. [1] [2] In this usage an escarpment is a ridge which has a gentle slope on one side and a steep scarp on the other side.

More loosely, the term scarp also describes a zone between a coastal lowland and a continental plateau which shows a marked, abrupt change in elevation [3] caused by coastal erosion at the base of the plateau.

Formation and description

Scarps are generally formed by one of two processes: either by differential erosion of sedimentary rocks, or by movement of the Earth's crust at a geologic fault. The first process is the more common type: the escarpment is a transition from one series of sedimentary rocks to another series of a different age and composition. 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.

Schematic cross section of a cuesta, dip slopes facing left, and harder rocklayers in darker colors than softer ones Cuesta schematic1.PNG
Schematic cross section of a cuesta, dip slopes facing left, and harder rocklayers in darker colors than softer ones

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 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 chain of hills squeezed between the fault and the mountains of New Zealand's Southern Alps. Northeast is towards the top. Alpine Fault SRTM (vertical).jpg
Shaded and colored image 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 chain of hills squeezed between the fault and the mountains of New Zealand's Southern Alps. Northeast is towards the top.

Erosion

When sedimentary beds are tilted and exposed to the surface, erosion and weathering may occur. Escarpments erode gradually and over geological time. The mélange tendencies of escarpments results in varying contacts between a multitude of rock types. These different rock types weather at different speeds, according to Goldich dissolution series so different stages of deformation can often be seen in the layers where the escarpments have been exposed to the elements.

Significant escarpments

Africa

Antarctica

Asia

Australia and New Zealand

Europe

The Sierra Escarpment in California SierraEscarpmentCA.jpg
The Sierra Escarpment in California

North America

At the Florida Escarpment, seen in the eastern Gulf of Mexico, the sea bed drops precipitously from less than 300 to 3,000 m (1,000 to 10,000 ft) over a short distance. Fixed gulf map.png
At the Florida Escarpment, seen in the eastern Gulf of Mexico, the sea bed drops precipitously from less than 300 to 3,000 m (1,000 to 10,000 ft) over a short distance.

South America

See also

Related Research Articles

<span class="mw-page-title-main">Darling Scarp</span> Scarp east of Perth, Western Australia

The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north–south to the east of the Swan Coastal Plain and Perth, Western Australia. The escarpment extends generally north of Bindoon, to the south of Pemberton. The adjacent Darling Plateau goes easterly to include Mount Bakewell near York and Mount Saddleback near Boddington. It was named after the Governor of New South Wales, Lieutenant-General Ralph Darling.

<span class="mw-page-title-main">Niagara Escarpment</span> Escarpment in Canada and the United States

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 which the Niagara River plunges at Niagara Falls, for which it is named.

<span class="mw-page-title-main">Cliff</span> Tall, near vertical rock face

In geography and geology, a cliff is an area of rock which has a general angle defined by the vertical, or nearly vertical. Cliffs are formed by the processes of weathering and erosion, with the effect of gravity. Cliffs are common on coasts, in mountainous areas, escarpments and along rivers. Cliffs are usually composed of rock that is resistant to weathering and erosion. The sedimentary rocks that are most likely to form cliffs include sandstone, limestone, chalk, and dolomite. Igneous rocks such as granite and basalt also often form cliffs.

<span class="mw-page-title-main">Intermontane Plateaus</span>

In the context of physical geography, the Intermontane Plateaus is one of eight physiographic regions of the contiguous United States. The region consists mostly of plateaus and mountain ranges lying between the Rocky Mountains on the east and the Cascade and Sierra Nevada Mountains on the west. It is subdivided into three physiographic provinces: the Columbia Plateau in the north, the Basin and Range Province in the central and southwestern portions, and the Colorado Plateau in the southeast. In turn, each of these provinces are each subdivided into a number of physiographic sections.

<span class="mw-page-title-main">Slump (geology)</span> Short distance movement of coherent earth down a slope

A slump is a form of mass wasting that occurs when a coherent mass of loosely consolidated materials or a rock layer moves a short distance down a slope. Movement is characterized by sliding along a concave-upward or planar surface. Causes of slumping include earthquake shocks, thorough wetting, freezing and thawing, undercutting, and loading of a slope.

<span class="mw-page-title-main">Stack (geology)</span> Geological landform consisting of a steep and often vertical column or columns of rock

A stack or sea stack is a geological landform consisting of a steep and often vertical column or columns of rock in the sea near a coast, formed by wave erosion. Stacks are formed over time by wind and water, processes of coastal geomorphology. They are formed when part of a headland is eroded by hydraulic action, which is the force of the sea or water crashing against the rock. The force of the water weakens cracks in the headland, causing them to later collapse, forming free-standing stacks and even a small island. Without the constant presence of water, stacks also form when a natural arch collapses under gravity, due to sub-aerial processes like wind erosion. Erosion causes the arch to collapse, leaving the pillar of hard rock standing away from the coast—the stack. Eventually, erosion will cause the stack to collapse, leaving a stump. Stacks can provide important nesting locations for seabirds, and many are popular for rock climbing.

Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.

<span class="mw-page-title-main">Mesa</span> Elevated area of land with a flat top and sides that are usually steep cliffs

A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.

<span class="mw-page-title-main">North Downs</span> Range of hills in south east England, UK

The North Downs are a ridge of chalk hills in south east England that stretch from Farnham in Surrey to the White Cliffs of Dover in Kent. Much of the North Downs comprises two Areas of Outstanding Natural Beauty (AONBs): the Surrey Hills and the Kent Downs. The North Downs Way National Trail runs along the North Downs from Farnham to Dover.

<span class="mw-page-title-main">Cumberland Mountains</span> Mountain range in the southeastern United States

The Cumberland Mountains are a mountain range in the southeastern section of the Appalachian Mountains. They are located in western Virginia, southwestern West Virginia, the eastern edges of Kentucky, and eastern middle Tennessee, including the Crab Orchard Mountains. Their highest peak, with an elevation of 4,223 feet (1,287 m) above mean sea level, is High Knob, which is located near Norton, Virginia.

<span class="mw-page-title-main">Cuesta</span> Hill or ridge with a gentle slope on one side and a steep slope on the other

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 strata, called caprock. Where erosion has exposed the frontslope of this, a steep slope or escarpment occurs. The resulting terrain may be called scarpland.

<span class="mw-page-title-main">Dip slope</span>

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. A dip slope consists of the upper surface of a resistant layer of rock, often called caprock, that is commonly only slightly lowered and reduced in steepness by erosion. Dip slopes form the backslopes of cuestas, homoclinal ridges, hogbacks, and flatirons. The frontslopes of such ridges consist of either an escarpment, a steep slope, or perhaps even a line of cliffs. Generally, cuestas and homoclinal ridges are asymmetrical in that their dip slopes are less steep than their escarpments. In the case of hogbacks and flatirons, the dip of the rocks is so steep that their dip slope approaches the escarpment in their steepness.

<span class="mw-page-title-main">Lincoln Cliff</span>

The Lincoln Cliff or Lincoln Edge is a portion of a major escarpment that runs north–south through Lindsey and Kesteven in central Lincolnshire and is a prominent landscape feature in a generally flat portion of the county. Towards its northern end, near Scunthorpe, it is sometimes referred to as the Trent Cliff. The name preserves an obsolete sense of the word "cliff", which could historically refer to a hillside as well as a precipitous rock face.

<span class="mw-page-title-main">Great Escarpment, Southern Africa</span> Major topographical feature in southern Africa

The Great Escarpment is a major topographical feature in Africa that consists of steep slopes from the high central Southern African plateau downward in the direction of the oceans that surround southern Africa on three sides. While it lies predominantly within the borders of South Africa, in the east the escarpment extends northward to form the border between Mozambique and Zimbabwe, continuing on beyond the Zambezi river valley to form the Muchinga Escarpment in eastern Zambia. In the west, it extends northward into Namibia and Angola.

<span class="mw-page-title-main">Lomond Hills</span> Range of hills in central Scotland

The Lomond Hills, also known outside the locality as the Paps of Fife, are a range of hills in central Scotland. They lie in western central Fife and Perth and Kinross, Scotland. At 522 metres (1,713 ft) West Lomond is the highest point in the county of Fife.

<span class="mw-page-title-main">Hogback (geology)</span> Long, narrow ridge

In geology and geomorphology, a hogback or hog's back is a long, narrow ridge or a series of hills with a narrow crest and steep slopes of nearly equal inclination on both flanks. Typically, the term is restricted to a ridge created by the differential erosion of outcropping, steeply dipping, homoclinal, and typically sedimentary strata. One side of a hogback consists of the surface of a steeply dipping rock stratum called a dip slope. The other side is an erosion face that cuts through the dipping strata that comprises the hogback. The name "hogback" comes from the Hog's Back of the North Downs in Surrey, England, which refers to the landform's resemblance in outline to the back of a hog. The term is also sometimes applied to drumlins and, in Maine, to both eskers and ridges known as "horsebacks".

<span class="mw-page-title-main">Homoclinal ridge</span> Ridge with a moderate sloping backslope and steeper frontslope

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 other side of the other slope, which is its frontslope, of a homoclinal ridge is a steeper or even cliff-like frontslope (escarpment) that is formed by the outcrop of the caprock. The escarpment cuts through the dipping strata that comprises the homoclinal ridge.

<span class="mw-page-title-main">Nilokeras Scopulus</span> Geologic feature of Mars

Nilokeras Scopulus is a long escarpment (cliff) in the northern hemisphere of the planet Mars. It is located along the southeastern boundary of the Tempe Terra plateau and forms the northern valley wall of the downstream portion of the immense Kasei Valles outflow channel system. The escarpment is 765 km long and ranges from 1 to a little over 2 km (3300–6600 ft) in height.

<span class="mw-page-title-main">Cliffed coast</span> Coast where waves have formed steep cliffs

A cliffed coast, also called an abrasion coast, is a form of coast where the action of marine waves has formed steep cliffs that may or may not be precipitous. It contrasts with a flat or alluvial coast.

<span class="mw-page-title-main">Scarp retreat</span>

Scarp retreat is a geological process through which the location of an escarpment changes over time. Typically the cliff is undermined, rocks fall and form a talus slope, the talus is chemically or mechanically weathered and then removed through water or wind erosion, and the process of undermining resumes. Scarps may retreat for tens of kilometers in this way over relatively short geological time spans, even in arid locations.

References

  1. Easterbrook, Don J. (1999). Surface Processes and Landforms. Prentice Hall. ISBN   978-0-13-860958-0.[ page needed ]
  2. Summary: Escarpments, US Army Corps of Engineers.
  3. "Scarps and Terraces". Physiography. Radford University. Retrieved 24 December 2020.
  4. Lidmar-Bergström, Karna (1988). "Denudation surfaces of a shield area in southern Sweden". Geografiska Annaler . 70 A (4): 337–350. doi:10.2307/521267. JSTOR   521267.
  5. Wörner, Gerhard; Uhlig, Dieter; Kohler, Ingrid; Seyfried, Hartmut (15 February 2002). "Evolution of the West Andean Escarpment at 18°S (N. Chile) during the last 25 Ma: uplift, erosion and collapse through time". Tectonophysics. 345 (1): 183–198. Bibcode:2002Tectp.345..183W. doi: 10.1016/S0040-1951(01)00212-8 .