Cycle of erosion

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 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 old 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. 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. The nature of surface processes is also poorly represented by the model. 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==

(1850–1934), the creator of the model Background There had been some ideas on cyclical erosion in the Graeco-Roman world and then in the Islamic world and Europe during the Middle Ages. 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 (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, 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, 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 and recapitulation both of which are linked to Neo-Lamarckianism. Darwin's evolution theory 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". 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, 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. 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. 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. 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. In 1960 geomorphologist Sheldon Judson noted that American geographers had largely abandoned the concept and moved to study landscape and landforms from a process and statistical 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. 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 and drainage density evolution in the erosion cycle have been criticized. 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. 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==