The term "peneplain" refers to an area that resembles a plain. It is created by river and rain erosion, which continues until nearly all of the elevated sections are eroded; the most resistant rocks typically rise above the land's general level. When a peneplain is raised, it becomes a Plateau, which is then dissected by the river as they cycle through youth and old age.
A peneplain is a low-relief plain created by long-term erosion in geomorphology and geology. This is the broadest concept, though the term peneplain is often used to refer to a near-final (or penultimate) stage of fluvial erosion during periods of prolonged tectonic stability. Peneplains are often synonymous with William Morris Davis's period of erosion theory, but Davis and others have often used the concept in a strictly descriptive sense without any theory or specific genesis attached.
Owing to a lack of contemporary examples and difficulty in recognizing relic examples, the presence of certain peneplains and peneplanation as a natural process is not without controversy. Peneplains grade down to a base level represented by sea level in some meanings, but this condition is ignored in others. The base-level criterion is important, according to geomorphologist Karna Lidmar-Bergström and colleagues, and it is above the precise mechanism of peneplain formation, which includes some pediplains among peneplains.
Although peneplains are normally thought to form near sea level, it has been suggested that they can form at a higher elevation if substantial sedimentation increases the local base level enough or tectonic deformation continuously obstructs river networks. These two instances can be exemplified by the Pyrenees peneplains and the Tibetan Plateau, respectively.
A popular misconception about peneplains is that they should be featureless in appearance. In reality, some peneplains may be hilly due to erratic deep weathering, resulting in a plain that only grads to a base level on a grand scale.
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Rivers, glaciers, and winds break off and carry away rock fragments from mountain and plateau surfaces. As a result, these landforms, mountains, and plateaus are gradually lowered, and their rough surfaces smoothed out to form nearly flat plains. PENEPLAINS are the name given to these plains.
Types of Peneplains
Landforms that are either alternatives to classical peneplains, a subset of peneplains, or partly overlap with the term are referred to by a variety of names. Last but not least, there are planation surfaces that may or may not be peneplains, and certain peneplains are not planation surfaces.
Green, Lidmar-Bergström, and coworkers propose the following classification scheme for peneplains in their 2013 paper:
Surfaces for Plantation
Peneplains may have been formed by etchplanation during periods of humid climate and pediplanation during periods of arid and semi-arid climate, according to Rhodes Fairbridge and Charles Finkl. Since some peneplains grow over long periods of time, they are subject to a wide range of climatic influences. Marine abrasion and glacial erosion are also listed as processes that can help shape peneplains by the same authors. Epigene peneplains are also distinguishable from exhumed peneplains. Peneplains that have never been buried or covered by sedimentary rock are known as epigene peneplains. Peneplains that have been re-exposed after being buried in sediments are known as exhumed peneplains.
Preservation and Destruction of Peneplains
Peneplains that have been uplifted or that have been separated from their base level can be marked by an accumulation of sediments that have buried them. The peneplain is preserved by burial. A paleo surface or paleo plan is any exposed peneplain that has been separated from its base level. Renewed erosion is typical when a peneplain is uplifted.
In extreme aridity or under non-eroding cold-based glacier ice, uplifted peneplains may be preserved as fossil landforms. In shield regions, glacier erosion of peneplains is minimal. During the Quaternary, glacier erosion averaged tens of meters in the Fennoscandian Shield, but it was not uniformly distributed. A long "preparation time" of weathering under non-glacial conditions may be required for glacier erosion to be successful in shields.
Peneplain surfaces exposed to subtropical and tropical climates for an extended period can be silicified, which can shield them from erosion.