The geographic cycle, or cycle of erosion, is an idealized
model
A model is an informative representation of an object, person, or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin , .
Models can be divided in ...
that explains the development of
relief
Relief is a sculpture, sculptural method in which the sculpted pieces remain attached to a solid background of the same material. The term ''wikt:relief, relief'' is from the Latin verb , to raise (). To create a sculpture in relief is to give ...
in
landscapes.
[ The model starts with the ]erosion
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
that follows uplift of land above a base level
In geology and geomorphology a base level is the lower limit for the vertical position of an erosion, erosion process. The modern term was introduced by John Wesley Powell in 1875. The term was subsequently appropriated by William Morris Davis wh ...
and ends, if conditions allow, in the formation of a peneplain. Landscapes that show evidence of more than one cycle of erosion are termed "polycyclical".[ The cycle of erosion and some of its associated concepts have, despite their popularity, been a subject of much criticism.
]
Description
William Morris Davis, the originator of the model, divided it into stages whose transition is gradual similar to the human life i.e. Youth Stage, Mature Stage and Old Stage. The model begins with an uplifted sate of landscape. Then Davis defined a ''youthful'' stage where river incision
River incision is the narrow erosion caused by a river or stream that is far from its base level. River incision is common after tectonic uplift of the landscape. Incision by multiple rivers result in a dissected landscape, for example a dissected ...
or vertical erosion is the dominant process shaping the landscape. During the ''youthful'' stage height, differences between uplands and valley bottoms increase rapidly. The ''youthful'' stage is followed by a ''mature'' stage in which height differences between valley bottoms and uplands are at their greatest. In the ''mature'' stage, slope decline becomes a more important phenomenon as the lateral erosion dominates, and uplands lose height more rapidly than rivers incise, effectively diminishing relief. In the very latest stage, erosion has acted so long that the landscape, despite its original height, is reduced into a ''rolling lowland''. That landscape of low relief is called a peneplain and may contain residual heights standing out from the general level. The peneplain can be uplifted, which starts a second erosion cycle.
Davis acknowledged that a full cycle was a special case and that initial uplift was not necessarily rapid or followed by a prolonged period of quiescence. However, as Walther Penck pointed out, Davis and his followers usually used a rapid uplift and quiescence approach to explain landscapes. This means that the model, as understood by most, assumes rapid and episodic tectonic uplift.[
Another characteristic of the model is that slopes evolve by decline, with initially-steep slopes worn out by erosion forming successively-gentler slopes.] Weaknesses of the model are that it is mostly theoretical and deductive in nature and it does not take into account the complexity of tectonic movements or climate change
Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...
. The nature of surface processes is also poorly represented by the model.[ The model in its original form is intended to explain relief development in temperate landscapes in which erosion by running water is assumed to be of prime importance.][ Nevertheless, the cycle of erosion has been extended, with modifications, into ]arid
Aridity is the condition of geographical regions which make up approximately 43% of total global available land area, characterized by low annual precipitation, increased temperatures, and limited water availability.Perez-Aguilar, L. Y., Plata ...
, semi-arid
A semi-arid climate, semi-desert climate, or steppe climate is a aridity, dry climate sub-type. It is located on regions that receive precipitation below Evapotranspiration#Potential evapotranspiration, potential evapotranspiration, but not as l ...
, savanah, selva
Selva may refer to:
People
*Selva (surname)
*Selva (name)
*Selva (actor), Indian actor
*Selva (director), Indian director
Places
*Selva (comarca), a coastal comarca (county) in Catalonia, Spain
*Selva, Mallorca (pop. 3,055), a municipality on Mal ...
, glacial
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
, coastal, karst
Karst () is a topography formed from the dissolution of soluble carbonate rocks such as limestone and Dolomite (rock), dolomite. It is characterized by features like poljes above and drainage systems with sinkholes and caves underground. Ther ...
and periglacial areas. Writing in 1950 Louis C. Peltier claimed the cycle of erosion in maritime and boreal climates were the only one that had not been described in detail.[
]
History

Background
There had been some ideas on cyclical erosion in the Graeco-Roman world and then in the Islamic world
The terms Islamic world and Muslim world commonly refer to the Islamic community, which is also known as the Ummah. This consists of all those who adhere to the religious beliefs, politics, and laws of Islam or to societies in which Islam is ...
and Europe during the Middle Ages
In the history of Europe, the Middle Ages or medieval period lasted approximately from the 5th to the late 15th centuries, similarly to the post-classical period of global history. It began with the fall of the Western Roman Empire and ...
. However the immediate influences of William Morris Davis, the creator of the cycle of erosion model, were 19th century American explorers. The end of the American Civil War
The American Civil War (April 12, 1861May 26, 1865; also known by Names of the American Civil War, other names) was a civil war in the United States between the Union (American Civil War), Union ("the North") and the Confederate States of A ...
(1861–1865) led to a resumption of the exploration of the western United States. Three explorers, John Wesley Powell, Clarence Edward Dutton and Grove Karl Gilbert
Grove Karl Gilbert (May 6, 1843 – May 1, 1918), known by the abbreviated name G. K. Gilbert in academic literature, was an American geologist.
Biography
Gilbert was born in Rochester, New York, and graduated from the University of Rochester. ...
, wrote about the geomorphology and geology in the landscapes they encountered. It was from these works that Davis borrowed many concepts used to construct the model.
It has been argued that Davis was also influenced by ideas from the field of biology
Biology is the scientific study of life and living organisms. It is a broad natural science that encompasses a wide range of fields and unifying principles that explain the structure, function, growth, History of life, origin, evolution, and ...
, especially the Neo-Lamarckian thought that was current in the late 19th-century United States. It is thought that Davis received some of this Neo-Lamarckian influence from his tutor, Nathaniel Shaler. Other biological theories that may have shaped the cycle of erosion are those of orthogenesis
Orthogenesis, also known as orthogenetic evolution, progressive evolution, evolutionary progress, or progressionism, is an Superseded theories in science, obsolete biological hypothesis that organisms have an innate tendency to evolution, evolve ...
and recapitulation both of which are linked to Neo-Lamarckianism. Darwin's evolution theory
Evolution is the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certai ...
was a lesser influence relative to Neo-Lamarckism. The impact of these ideas can be hinted in the models' employment of the concept of "evolution" rather than "change", implying a predictable direction of landscape and landform change. It has been argued that "Davis consciously applied Darwinism to landscape".[
]
Early acclaim and criticism
Davis conceived the cycle of erosion model in the 1880s while studying the Appalachians in Pennsylvania
Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...
and Virginia
Virginia, officially the Commonwealth of Virginia, is a U.S. state, state in the Southeastern United States, Southeastern and Mid-Atlantic (United States), Mid-Atlantic regions of the United States between the East Coast of the United States ...
.[ Davis wrote down the Cycle of erosion theory in detail for the first time in 1889.][ More fully developed by 1900 it received wide acclaim, but was never universally accepted.][ The initial enthusiasm and strength of the cycle of erosion model has been attributed to various causes. First, the model provided a framework to study areas and epochs in Earth history where ]erosion
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
is the dominant process. Second, the model fitted well into the grand evolutionary thought that had emerged in the 19th century with Darwin's evolution theory
Evolution is the change in the heritable characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certai ...
.[ Lastly, some popularity can be attributed to Davis's lucid writing style. The model achieved its greatest popularity in the 1900–39 period when numerous studies on denudation chronology based on the model were published. In these studies usually two to five erosion cycles were identified. The approach of doing denudation chronology with the cycle of erosion model lost popularity from the 1930s onward.][ Arguably this was so because the approach did not provide any unforeseeable insights. An increasing number of geomorphologists had begun to study processes happening in the present and not in the past as done with the cycle of erosion model. These process geomorphologists soon realized some of their observations were at odds with Davis's model. Other geomorphologists turned away from the cycle of erosion to work instead on climatic or tectonic geomorphology.]
The model spread fast. In 1901 Hans Reusch was using it to explain the undulating plateau of southern Norway. Very much influenced by Davis Walter Wråk moved to study the relief of the northern Scandinavian Mountains
The Scandinavian Mountains or the Scandes is a mountain range that runs through the Scandinavian Peninsula. The western sides of the mountains drop precipitously into the North Sea and Norwegian Sea, forming the fjords of Norway, whereas to th ...
, describing among other things the Borsu surface.
The first study of China's topography using the model was published in 1907 by B. Willis and co-workers. The idea of the cycle of erosion was disseminated among college and university students with a series of textbooks published in the 1890s and 1900s.[ According to Sheldon Judson up to ]Second World War
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
reports on regional geology tended to include brief mentions of the local cycle of erosion and of peneplanization.[
While the model was at first widely accepted among ]Anglo-Saxon
The Anglo-Saxons, in some contexts simply called Saxons or the English, were a Cultural identity, cultural group who spoke Old English and inhabited much of what is now England and south-eastern Scotland in the Early Middle Ages. They traced t ...
scholars,[ in ]Continental Europe
Continental Europe or mainland Europe is the contiguous mainland of Europe, excluding its surrounding islands. It can also be referred to ambiguously as the European continent, – which can conversely mean the whole of Europe – and, by som ...
it met some resistance with German scholars Albrecht and Walther Penck, Siegfried Passarge and Alfred Hettner standing out as early opponents to the model. Despite Davis's efforts, which included translating his work into German, being a visiting professor at Berlin and touring much of Europe, the cycle of erosion never did take firm root in Germany.[ Walther Penck came to originate an alternative model with its own set of tenets. Walther's ideas were published posthumously in 1924 by his father, Albrecht. In Walther's model, relief is shaped as a function of the denudation/uplift rate.][ Davis, a friend of Walther's father, was critical of Walther's new model. Davis's review of Walther Penck's second publication on the subject left a distorted view of Penck's ideas among later workers. This is because Davis misunderstood and mis-translated parts of the paper, therefore Davis is not an adequate critic of Penck's work.]
In France the cycle of erosion theory was first spread by Albert de Lapparent
Albert Auguste Cochon de Lapparent (30 December 18395 May 1908) was a French geologist.
Life
He was born at Bourges. After studying at the École polytechnique from 1858 to 1860 he became ''ingénieur au corps des mines'', and took part in drawi ...
. In general its reception in France was mixed with Émile Haug giving it limited attention and Paul Vidal de La Blache adopting it without reservations. Other notable French geographers influenced by Davis ideas on the cycle of erosion are Emmanuel de Martonne and Henri Baulig.[ Geomorphology in France developed into two schools, one based on geographers who adopted Davisian thought and another based on ]engineering geology
Engineering geology is the application of geology to engineering study for the purpose of assuring that the geological factors regarding the location, design, construction, operation and maintenance of engineering works are recognized and accou ...
with connections to hydraulics
Hydraulics () is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counterpart of pneumatics, which concer ...
and mining
Mining is the Resource extraction, extraction of valuable geological materials and minerals from the surface of the Earth. Mining is required to obtain most materials that cannot be grown through agriculture, agricultural processes, or feasib ...
.[
]
Intensified criticism (1945–1974)
200px, (1927–2002), a geomorphologist known for his criticism of the cycle of erosion. In Richard Chorley (1927–2002), a geomorphologist known for his criticism of the cycle of erosion. In 's words Davis bashing' was a theme" for him.">Cliff Ollier">Richard Chorley (1927–2002), a geomorphologist known for his criticism of the cycle of erosion. In Cliff Ollier's words Davis bashing' was a theme" for him.
In 1960 geomorphologist Sheldon Judson noted that American geographers had largely abandoned the concept and moved to study landscape and landforms from a
process
A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic.
Things called a process include:
Business and management
* Business process, activities that produce a specific s ...
and geostatistics">statistical
Statistics (from German language, German: ', "description of a State (polity), state, a country") is the discipline that concerns the collection, organization, analysis, interpretation, and presentation of data. In applying statistics to a s ...
point of view. Eiju Yatsu opined, however, that despite the intention of many geomorphologists to abandon Davisian ideas after the Second World War, many ended up returning to them with some modifications.
An alternative cycle theory was proposed by Lester Charles King in the 1960s.[ While King's ideas were an attempt at refuting Davis's cycle of erosion they were themselves of cyclical nature and contributed to ushering in a wave of criticism in 1960s against both his and Davis's models.][ This criticism has been called "Davis bashing" by Cliff Ollier and constitutes to Ollier the ridicule of cyclical theories in geomorphology without any alternative model being proposed.] Since Davis' ideas were being discredited other areas of research, like that of climatic geomorphology, were attacked by their perceived association to it.
The notions of time, uplift, slope
In mathematics, the slope or gradient of a Line (mathematics), line is a number that describes the direction (geometry), direction of the line on a plane (geometry), plane. Often denoted by the letter ''m'', slope is calculated as the ratio of t ...
and drainage density
Drainage density is a quantity used to describe physical parameters of a drainage basin. First described by Robert E. Horton, drainage density is defined as the total length of channel in a drainage basin divided by the total area, represented by ...
evolution in the erosion cycle have been criticized.[ Further the validity of some whole concepts associated with the cycle of erosion have been questioned including stream grade,][ slope decline, ]base level
In geology and geomorphology a base level is the lower limit for the vertical position of an erosion, erosion process. The modern term was introduced by John Wesley Powell in 1875. The term was subsequently appropriated by William Morris Davis wh ...
[ and most of all that of peneplains.][
Writing in 1971 geomorphologist Ronald Flemal summarized the situation as follows:][
:''Currently geomorphologists are divided into three camps: those who still adhere to Davisian concepts, either in the original or a modified form; those who desire to replace Davisian ideas by a different cyclic erosional model; and those who reject cyclic erosion completely.''
]
Modern status
Despite considerable criticism the cycle of erosion model has remained part of the science of geomorphology
Geomorphology () is the scientific study of the origin and evolution of topographic and bathymetric features generated by physical, chemical or biological processes operating at or near Earth's surface. Geomorphologists seek to understand wh ...
.[ The model or theory has never been proved wrong,][ but neither has it been proven.] The inherent difficulties of the model have instead made geomorphological research to advance along other lines. In contrast to its disputed status in geomorphology, the cycle of erosion model is a common approach used to establish denudation chronologies, and is thus an important concept in the science of historical geology
Historical geology or palaeogeology is a discipline that uses the principles and methods of geology to reconstruct the geological history of Earth. Historical geology examines the vastness of geologic time, measured in billions of years, and inv ...
. While acknowledging its shortcomings modern geomorphologists Andrew Goudie and Karna Lidmar-Bergström have praised it for its elegance and pedagogical value respectively.[ Writing in 2007 Anthony Orme evaluates that:][
:''"stripped of its evolutionary baggage, the Davisian Cycle of Erosion had merit as an interpretive exercise, and indeed still has merit as an end-member in a range of possible temporal scenarios for Earth’s surface development."''
]
See also
* Epigenetic valley
* Fluvial landforms
Landforms related to rivers and other watercourses include:
*
*
*
*
* (watershed)
*
*
*Fluvial landforms of streams
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and ban ...
* Rejuvenation (river)
In geomorphology a river is said to be rejuvenated when it is eroding the landscape in response to a lowering of its base level. River rejuvenation refers to the renewed erosive activity of a river and can increase as a rivers flow increases. The ...
Notes
References
Sources
*Don J. Easterbrook (1999)
Surface Processes and Landforms
Second Edition; Chapter Six
*
*
External links
Illustrations edited by The Association of Polish Geomorphologists. Retrieved January 10, 2016.
{{DEFAULTSORT:Cycle Of Erosion
Geomorphology models
Erosion