A gully is a landform created by running water, mass movement, or commonly a combination of both eroding sharply into soil or other relatively erodible material, typically on a hillside or in river floodplains or terraces. Gullies resemble large ditches or small valleys, but are metres to tens of metres in depth and width and are characterised by a distinct 'headscarp' or 'headwall' and progress by headward (i.e. upstream) erosion. Gullies are commonly related to intermittent or ephemeral water flow usually associated with localised intense or protracted rainfall events, or snowmelt. Gullies can be formed and accelerated by cultivation practices on hillslopes (often gentle gradient) in farmland, and they can develop rapidly in rangelands from existing natural erosion forms subject to vegetative cover removal and livestock activity.
The earliest known usage of the term is from 1657. It originates from the French word goulet, a diminutive form of goule which means throat. It is possible that the term is connected to the name of a type of knife used at the time, a gully-knife.[citation needed]
Formation and consequencesEdit
Gully erosion can progress through a variety and combination of processes. The erosion processes include incision and bank erosion by water flow, mass movement of saturated or unsaturated bank or wall material, groundwater seepage - sapping the overlying material, collapse of soil pipes or tunnels in dispersive soils, or a combination of these to a greater or lesser degree. Hillsides are more prone to gully erosion when they are cleared of vegetation cover, through deforestation, over-grazing or other means. Gullies in rangelands can be initiated by concentrated water flow down tracks worn by livestock or vehicle tracks. The eroded soil is easily carried by the flowing water after being dislodged from the ground, normally when rainfall falls during short, intense storms such as during thunderstorms.
Gullies reduce the productivity of farmlands where they incise into the land, and produce sediment that may choke downstream waterbodies, and reduce water quality within the drainage system and lake or coastal system. Because of this, much effort is invested into the study of gullies within the scope of geomorphology and soil science, in the prevention of gully erosion, and in remediation and rehabilitation of gullied landscapes. The total soil loss from gully formation and subsequent downstream riversedimentation can be substantial, especially from unstable soil materials prone to dispersion.
Artificial gulliesEdit
Gullies can be formed or enlarged by a number of human activities.
Artificial gullies are formed during hydraulic mining when jets or streams of water are projected onto soft alluvial deposits to extract gold or tin ore. The remains of such mining methods are very visible landform features in old goldfields such as in California and northern Spain. The badlands at Las Medulas for example, were created during the Roman period by hushing or hydraulic mining of the gold-rich alluvium with water supplied by numerous aqueducts tapping nearby rivers. Each aqueduct produced large gullies below by erosion of the soft deposits. The effluvium was carefully washed with smaller streams of water to extract the nuggets and gold dust.[citation needed]
Gullies are widespread at mid- to high latitudes on the surface of Mars, and are some of the youngest features observed on that planet, probably forming within the last few 100,000 years. There, they are one of the best lines of evidence for the presence of liquid water on Mars in the recent geological past, probably resulting from the slight melting of snowpacks on the surface[1] or ice in the shallow subsurface[2] on the warmest days of the Martian year. Flow as springs from deeper seated liquid water aquifers in the deeper subsurface is also a possible explanation for the formation of some Martian gullies.[3]
Draw (terrain) – Terrain feature formed by two parallel ridges or spurs with low ground in betweenPages displaying short descriptions of redirect targets
Lavaka – Type of gully, formed via groundwater sapping
Linn (geography) – gully in Scotland or Northern England in rock
Ravine – Small valley, often due to stream erosion
Rill – Shallow channel cut by water – a shallow channel cut into soil by erosion from flowing water
Terrace Crossing - a geographical zone between the sedimentation (downstream) part and the erosion (upstream) part of a river
Wadi – River valley, especially a dry riverbed that contains water only during times of heavy rain
ReferencesEdit
Oxford English Dictionary
^Christensen, PR (2003). "Formation of recent martian gullies through melting of extensive water-rich snow deposits.". Nature 422 (6927): 45–8. doi:10.1038/nature01436. PMID 12594459.
^Costard, F. , Forget, F. , Mangold, N. & Peulvast, J. P. Formation of recent martian debris flows by melting of near-surface ground ice at high obliquity. Science 295, 110–113
^Malin M. C. and Edgett K. S. (2000) Science, 288, 2330–2335.
External linksEdit
Wikimedia Commons has media related to Gully.
October 21, 2023
gully, this, article, about, landform, other, uses, disambiguation, gully, landform, created, running, water, mass, movement, commonly, combination, both, eroding, sharply, into, soil, other, relatively, erodible, material, typically, hillside, river, floodpla. This article is about the landform For other uses see Gully disambiguation A gully is a landform created by running water mass movement or commonly a combination of both eroding sharply into soil or other relatively erodible material typically on a hillside or in river floodplains or terraces Gullies resemble large ditches or small valleys but are metres to tens of metres in depth and width and are characterised by a distinct headscarp or headwall and progress by headward i e upstream erosion Gullies are commonly related to intermittent or ephemeral water flow usually associated with localised intense or protracted rainfall events or snowmelt Gullies can be formed and accelerated by cultivation practices on hillslopes often gentle gradient in farmland and they can develop rapidly in rangelands from existing natural erosion forms subject to vegetative cover removal and livestock activity A gully in Kharkiv oblast Ukraine Gullied landscape in Somalia Contents 1 Etymology 2 Formation and consequences 3 Artificial gullies 4 On Mars 5 Gallery 6 See also 7 References 8 External linksEtymology EditThe earliest known usage of the term is from 1657 It originates from the French word goulet a diminutive form of goule which means throat It is possible that the term is connected to the name of a type of knife used at the time a gully knife citation needed Formation and consequences EditGully erosion can progress through a variety and combination of processes The erosion processes include incision and bank erosion by water flow mass movement of saturated or unsaturated bank or wall material groundwater seepage sapping the overlying material collapse of soil pipes or tunnels in dispersive soils or a combination of these to a greater or lesser degree Hillsides are more prone to gully erosion when they are cleared of vegetation cover through deforestation over grazing or other means Gullies in rangelands can be initiated by concentrated water flow down tracks worn by livestock or vehicle tracks The eroded soil is easily carried by the flowing water after being dislodged from the ground normally when rainfall falls during short intense storms such as during thunderstorms A gully may grow in length by means of headward i e upstream erosion at a knick point This erosion can result from interflow and soil piping internal erosion as well as surface runoff Gully erosion may also advance laterally by similar methods including mass movement acting on the gully walls banks and by developing branches a type of tributary Gullies reduce the productivity of farmlands where they incise into the land and produce sediment that may choke downstream waterbodies and reduce water quality within the drainage system and lake or coastal system Because of this much effort is invested into the study of gullies within the scope of geomorphology and soil science in the prevention of gully erosion and in remediation and rehabilitation of gullied landscapes The total soil loss from gully formation and subsequent downstream river sedimentation can be substantial especially from unstable soil materials prone to dispersion Artificial gullies EditGullies can be formed or enlarged by a number of human activities Artificial gullies are formed during hydraulic mining when jets or streams of water are projected onto soft alluvial deposits to extract gold or tin ore The remains of such mining methods are very visible landform features in old goldfields such as in California and northern Spain The badlands at Las Medulas for example were created during the Roman period by hushing or hydraulic mining of the gold rich alluvium with water supplied by numerous aqueducts tapping nearby rivers Each aqueduct produced large gullies below by erosion of the soft deposits The effluvium was carefully washed with smaller streams of water to extract the nuggets and gold dust citation needed On Mars EditMain article Gully Mars Gullies are widespread at mid to high latitudes on the surface of Mars and are some of the youngest features observed on that planet probably forming within the last few 100 000 years There they are one of the best lines of evidence for the presence of liquid water on Mars in the recent geological past probably resulting from the slight melting of snowpacks on the surface 1 or ice in the shallow subsurface 2 on the warmest days of the Martian year Flow as springs from deeper seated liquid water aquifers in the deeper subsurface is also a possible explanation for the formation of some Martian gullies 3 Gallery Edit nbsp A gully in Saratov Oblast Russia nbsp Inside the gully to the left in Saratov Oblast Russia nbsp Vocoroca Portuguese for gully in Avare Brasil nbsp Gully formed from volcanic sedimentation in West Java Indonesia nbsp A Gully formed by flood in Isuaniocha community of Anambra State NigeriaSee also EditArroyo creek Dry watercourse with flow after rainPages displaying short descriptions of redirect targets Badlands Type of heavily eroded terrain Coulee Type of valley or drainage zone Couloir Steep narrow mountain gully a narrow gully with a steep gradient in a mountainous terrain Dale landform Open valley Draw terrain Terrain feature formed by two parallel ridges or spurs with low ground in betweenPages displaying short descriptions of redirect targets Gulch Deep V shaped valley formed by erosion Lavaka Type of gully formed via groundwater sapping Linn geography gully in Scotland or Northern England in rock Ravine Small valley often due to stream erosion Rill Shallow channel cut by water a shallow channel cut into soil by erosion from flowing water Terrace Crossing a geographical zone between the sedimentation downstream part and the erosion upstream part of a river Wadi River valley especially a dry riverbed that contains water only during times of heavy rainReferences EditOxford English Dictionary Christensen PR 2003 Formation of recent martian gullies through melting of extensive water rich snow deposits Nature 422 6927 45 8 doi 10 1038 nature01436 PMID 12594459 Costard F Forget F Mangold N amp Peulvast J P Formation of recent martian debris flows by melting of near surface ground ice at high obliquity Science 295 110 113 Malin M C and Edgett K S 2000 Science 288 2330 2335 External links Edit nbsp Wikimedia Commons has media related to Gully Retrieved from https en wikipedia org w index php title Gully amp oldid 1169083671, wikipedia, wiki, book, books, library,
