An etchplain is a plain where the bedrock has been subject to considerable "etching" or subsurface weathering. Etchplanation is the process forming etchplains. Contrary to what the name might suggest, etchplains are seldom completely flat and usually display some relief, as weathering of the bedrock does not advance uniformly. This means that weathering is unrelated to the flatness which might be derivative of various other processes of planation including peneplanation and pediplanation.[1] Erosion of etchplains can result in the exposure of inselbergs such as bornhardt and tors.[2] Generally the topography exposed at a stripped etchplain, that is an etch surface,[3] after erosion of regolith is one with many irregularities as result of structurally defined areas of rock strength.[4]
A distinction can be made between etchplains and etch surfaces as the latter may or may not be flat and can represent the landform arising from the stripping of an etchplain.[3]
As climate changes, arid and semi-arid periods of pediplanation may alternate with more humid periods of etchplanation resulting in the formation of flattish surfaces (peneplains) of mixed origin (polygenetic).[5]
During wet seasons deep weathering is more pronounced producing regolith which is then stripped away by erosion during subsequent dry seasons.[6] The rate of stripping must exceed that of regolith production by deep weathering, otherwise deep-seated basal surfaces would not be revealed.
The African Surface formed 70–40 million years ago is an example of an etchplain.[2]
History of the concept
The term 'etchplain' or 'etched peneplain' was originally coined to describe surfaces in East Africa by E.J. Wayland in 1933 and Bailey Willis in 1936. This last geologist applied the term etched peneplain to the Tanganyika Plateau. Julius Büdel developed the concept further in the second half of the 20th century, but never did use the term 'etchplain'.[7] The term came for a long time to be associated with landscapes in the tropics or with a tropical climate but since the 1980s it has also been used to describe flat weathered landscapes at higher latitudes.[1]
See also
Strandflat – Type of landform found in high-latitude areas
^ abMigoń, Piotr (2004). "Etchning, etchplain and etchplanation". In Goudie, A.S. (ed.). Encyclopedia of Geomorphology. Routledge. pp. 345–347.
^ abGuillocheau, François; Simon, Brendan; Baby, Guillaume; Bessin, Paul; Robin, Cécile; Dauteuil, Olivier (2018). "Planation surfaces as a record of mantle dynamics: The case example of Africa" (PDF). Gondwana Research. 53: 82. Bibcode:2018GondR..53...82G. doi:10.1016/j.gr.2017.05.015.
^ abEbert, Karin (2009). "Terminology of long-term geomorphology: a Scandinavian perspective". Progress in Physical Geography. 33 (2): 163–182. doi:10.1177/0309133309338138. S2CID 128915651.
etchplain, etchplain, plain, where, bedrock, been, subject, considerable, etching, subsurface, weathering, etchplanation, process, forming, etchplains, contrary, what, name, might, suggest, etchplains, seldom, completely, flat, usually, display, some, relief, . An etchplain is a plain where the bedrock has been subject to considerable etching or subsurface weathering Etchplanation is the process forming etchplains Contrary to what the name might suggest etchplains are seldom completely flat and usually display some relief as weathering of the bedrock does not advance uniformly This means that weathering is unrelated to the flatness which might be derivative of various other processes of planation including peneplanation and pediplanation 1 Erosion of etchplains can result in the exposure of inselbergs such as bornhardt and tors 2 Generally the topography exposed at a stripped etchplain that is an etch surface 3 after erosion of regolith is one with many irregularities as result of structurally defined areas of rock strength 4 A distinction can be made between etchplains and etch surfaces as the latter may or may not be flat and can represent the landform arising from the stripping of an etchplain 3 As climate changes arid and semi arid periods of pediplanation may alternate with more humid periods of etchplanation resulting in the formation of flattish surfaces peneplains of mixed origin polygenetic 5 During wet seasons deep weathering is more pronounced producing regolith which is then stripped away by erosion during subsequent dry seasons 6 The rate of stripping must exceed that of regolith production by deep weathering otherwise deep seated basal surfaces would not be revealed The African Surface formed 70 40 million years ago is an example of an etchplain 2 History of the concept EditThe term etchplain or etched peneplain was originally coined to describe surfaces in East Africa by E J Wayland in 1933 and Bailey Willis in 1936 This last geologist applied the term etched peneplain to the Tanganyika Plateau Julius Budel developed the concept further in the second half of the 20th century but never did use the term etchplain 7 The term came for a long time to be associated with landscapes in the tropics or with a tropical climate but since the 1980s it has also been used to describe flat weathered landscapes at higher latitudes 1 See also EditStrandflat Type of landform found in high latitude areas Sub Mesozoic hilly peneplains Landscape in Scandinavia of undulating hills and joint valleysReferences Edit a b Migon Piotr 2004 Etchning etchplain and etchplanation In Goudie A S ed Encyclopedia of Geomorphology Routledge pp 345 347 a b Guillocheau Francois Simon Brendan Baby Guillaume Bessin Paul Robin Cecile Dauteuil Olivier 2018 Planation surfaces as a record of mantle dynamics The case example of Africa PDF Gondwana Research 53 82 Bibcode 2018GondR 53 82G doi 10 1016 j gr 2017 05 015 a b Ebert Karin 2009 Terminology of long term geomorphology a Scandinavian perspective Progress in Physical Geography 33 2 163 182 doi 10 1177 0309133309338138 S2CID 128915651 Planation surface Encyclopaedia Britannica Fairbridge Rhodes W Finkl Jr Charles W 1980 Cratonic erosion unconformities and peneplains The Journal of Geology 88 1 69 86 Bibcode 1980JG 88 69F doi 10 1086 628474 Inselberg Formation Theories The Geo Room Thomas David S G Goudie Andrew S eds 28 May 2013 etchplain The Dictionary of Physical Geography ISBN 978 1118687437 This geomorphology article is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Etchplain amp oldid 1086810375, wikipedia, wiki, book, books, library,
