Groundwater sapping is a geomorphic erosion process that results in the headward migration of channels in response to near constant fluid discharge at a fixed point. The consistent flow of water displaces fine sediments which physically and chemically weathers rocks.[1] Valleys that appear to have been created by groundwater sapping occur throughout the world in areas such as England, Colorado, Hawai’i, New Zealand, and many other places.[2] However, it is difficult to characterize a landform as being formed exclusively by groundwater sapping due to phenomena such as pluvial runoff, plunge-pool undercutting, changes in water table level, and inconsistent groundwater flow.[1] An example of drainage ways created purely by the outflow of subsurface fluids can be seen on the foreshores of beaches. As the surge of water and sand brought to land by a wave retreats seaward, the film of water becomes thinner until it forms rhomboid shaped patterns in the sand. Small fans form at the apex of the rhombic features, which are eventually fed by the remaining backflow of water traveling downslope. Channels begin to form headward in the form of millimeter wide rills along the sides of the fans; the creation of these small channel networks culminates when the last of the backwash dissipates.[1]
This is one of the processes involved in the formation of gullies, such as lavaka. Erosion by sapping tends to produce steep-sided U-shaped valleys of fairly uniform width with box-like, "theater-shaped" headwalls. This contrasts with the more common branching or dendritic pattern of V-shaped valleys produced by overland flows that become wider with distance from their source. Groundwater sapping has been suggested as the cause for erosion of the valley and channel networks on Mars, although studies show that groundwater alone can not excavate and transport the material required to create these canyons.[3]
Scientists believe that groundwater sapping created these gullies in Noachis Terra on Mars.[citation needed]NASA image.
Sapping typically occurs in permeable sandstones associated with high water tables underlain by an impermeable layer. Limited in its ability to travel vertically, water is forced to travel laterally where it eventually seeps out of the ground. Limestones, siltstones, and shales can be found in valleys created by groundwater sapping as well.[4]
Characteristic landformsEdit
Characteristic landforms caused by groundwater sapping are “theater-shaped” channel heads and “U-shaped” valleys, which have a consistent width and steep valley walls.[5] Weakened basal rocks are unable to support more resistant upper layers, causing valley head and sidewalls to collapse inwards.[5] Theater-shaped channel heads are characterized by overhanging sidewalls that are relatively dry compared to the lower level rocks below the zone of seepage.[2] The development of theater heads has been related to “ground-water flow direction, jointing and faulting, permeability contrasts, formation slope and dip angles, and formation cohesion”.[4] The morphology of channels and valleys created by sapping are highly dependent on regional scale geology, and can be hard to distinguish from features created through alternative processes. Chemical precipitates can be used as indicators of groundwater water discharge implying that a valley or channel may have been formed as a result of sapping. These sorts of clues are important in areas where water is not currently being discharged.[4]
Notable landmarksEdit
The two canyons at center-left in this photo from Canyonlands National Park in Utah have the theater-shaped heads typical of valley features shaped by groundwater sapping. The Green River is at right.
Many “natural amphitheaters” can be found near the Colorado River. It is thought that sapping may have been more common in this area in the past when there was a higher water table. A shift in the climate and associated precipitation or the incision of the Colorado River are two factors that may have caused a change in the water table level.[4]
Short, stream-like, deep channels have been observed on Mars. Very similar to valleys created by groundwater sapping here on Earth, the discovery of the Martian valleys has prompted numerous studies that aim to better understand the process of sapping.[6]
^ abcHiggins, C.G. (1984). "Piping and Sapping: Development of Landforms by Groundwater Outflow". In LaFleur, R.G. (ed.). Groundwater as a Geologic Agent. Boston, MA: Allen and Unwin. pp. 18–58.
^ abNash, D.J. (1996). "Groundwater Sapping and Valley Development in the Hackness Hills, North Yorkshire, England". Earth Surface Processes and Landforms (9 ed.). 21 (9): 781–795. Bibcode:1996ESPL...21..781N. doi:10.1002/(sici)1096-9837(199609)21:9<781::aid-esp616>3.0.co;2-o.
^Lamb, M. P.; Dietrich, W. E.; Aciego, S. M.; Depaolo, D. J.; Manga, M. (2008). "Formation of Box Canyon, Idaho, by Megaflood: Implications for Seepage Erosion on Earth and Mars" (PDF). Science. 320 (5879): 1067–1070. Bibcode:2008Sci...320.1067L. doi:10.1126/science.1156630. PMID 18497296. S2CID 30609556.
^ abcdRosenberry, Donald. "University of Colorado". Ground-water Sapping and the Generation of Natural Ampitheaters.
^ abKochel, R.C.; Piper, J.F. (1986). "Morphology of Large Valleys on Hawaii: Evidence for Groundwater Sapping and Comparisons with Martian Valleys". Journal of Geophysical Research. 91 (B13): 175–192. Bibcode:1986JGR....91E.175K. doi:10.1029/jb091ib13p0e175.
^Gulick, V.C. (2001). "Origin of the Valley Networks on Mars: a Hydrological Perspective". Geomorphology. 37 (3–4): 241–268. Bibcode:2001Geomo..37..241G. doi:10.1016/s0169-555x(00)00086-6. hdl:2060/20000092094.
External linksEdit
Simulation of Groundwater Sapping
Alan D. Howard, "Introduction: Groundwater Sapping on Mars and Earth" in Sapping Features of the Colorado Plateau, edited by A.D. Howard, R. C. Kochel, and H. R. Holt, NASA SP-491, p. 1-5 (1988)
Julie E. Laity and Michael C. Malin, "Sapping processes and the development of theater-headed valley networks on the Colorado Plateau," Geological Society of America Bulletin: Vol. 96, No. 2 (1985), pp. 203–217 (Abstract).
Stepinski, T.F.; Coradetti, S. (2004). "Comparing morphologies of drainage basins on Mars and Earth using integral-geometry and neural maps". Geophysical Research Letters. 31 (15): L15604. Bibcode:2004GeoRL..3115604S. doi:10.1029/2004GL020359.
Lou, W. (2000). "Quantifying Groundwater-sapping Landforms with a Hyposemetric Technique". Journal of Geophysical Research. 105 (1): 1685–1694. Bibcode:2000JGR...105.1685L. doi:10.1029/1999je001096.
October 17, 2023
groundwater, sapping, geomorphic, erosion, process, that, results, headward, migration, channels, response, near, constant, fluid, discharge, fixed, point, consistent, flow, water, displaces, fine, sediments, which, physically, chemically, weathers, rocks, val. Groundwater sapping is a geomorphic erosion process that results in the headward migration of channels in response to near constant fluid discharge at a fixed point The consistent flow of water displaces fine sediments which physically and chemically weathers rocks 1 Valleys that appear to have been created by groundwater sapping occur throughout the world in areas such as England Colorado Hawai i New Zealand and many other places 2 However it is difficult to characterize a landform as being formed exclusively by groundwater sapping due to phenomena such as pluvial runoff plunge pool undercutting changes in water table level and inconsistent groundwater flow 1 An example of drainage ways created purely by the outflow of subsurface fluids can be seen on the foreshores of beaches As the surge of water and sand brought to land by a wave retreats seaward the film of water becomes thinner until it forms rhomboid shaped patterns in the sand Small fans form at the apex of the rhombic features which are eventually fed by the remaining backflow of water traveling downslope Channels begin to form headward in the form of millimeter wide rills along the sides of the fans the creation of these small channel networks culminates when the last of the backwash dissipates 1 This is one of the processes involved in the formation of gullies such as lavaka Erosion by sapping tends to produce steep sided U shaped valleys of fairly uniform width with box like theater shaped headwalls This contrasts with the more common branching or dendritic pattern of V shaped valleys produced by overland flows that become wider with distance from their source Groundwater sapping has been suggested as the cause for erosion of the valley and channel networks on Mars although studies show that groundwater alone can not excavate and transport the material required to create these canyons 3 Scientists believe that groundwater sapping created these gullies in Noachis Terra on Mars citation needed NASA image Contents 1 Geomorphology and geology 2 Characteristic landforms 3 Notable landmarks 3 1 Colorado Plateau 3 2 Mars 4 See also 5 References 6 External linksGeomorphology and geology EditSapping typically occurs in permeable sandstones associated with high water tables underlain by an impermeable layer Limited in its ability to travel vertically water is forced to travel laterally where it eventually seeps out of the ground Limestones siltstones and shales can be found in valleys created by groundwater sapping as well 4 Characteristic landforms EditCharacteristic landforms caused by groundwater sapping are theater shaped channel heads and U shaped valleys which have a consistent width and steep valley walls 5 Weakened basal rocks are unable to support more resistant upper layers causing valley head and sidewalls to collapse inwards 5 Theater shaped channel heads are characterized by overhanging sidewalls that are relatively dry compared to the lower level rocks below the zone of seepage 2 The development of theater heads has been related to ground water flow direction jointing and faulting permeability contrasts formation slope and dip angles and formation cohesion 4 The morphology of channels and valleys created by sapping are highly dependent on regional scale geology and can be hard to distinguish from features created through alternative processes Chemical precipitates can be used as indicators of groundwater water discharge implying that a valley or channel may have been formed as a result of sapping These sorts of clues are important in areas where water is not currently being discharged 4 Notable landmarks Edit nbsp The two canyons at center left in this photo from Canyonlands National Park in Utah have the theater shaped heads typical of valley features shaped by groundwater sapping The Green River is at right Colorado Plateau Edit Main article Colorado Plateau Many natural amphitheaters can be found near the Colorado River It is thought that sapping may have been more common in this area in the past when there was a higher water table A shift in the climate and associated precipitation or the incision of the Colorado River are two factors that may have caused a change in the water table level 4 Mars Edit Main article Mars Short stream like deep channels have been observed on Mars Very similar to valleys created by groundwater sapping here on Earth the discovery of the Martian valleys has prompted numerous studies that aim to better understand the process of sapping 6 See also EditHeadward erosion Groundwater discharge Valley networks Mars References Edit a b c Higgins C G 1984 Piping and Sapping Development of Landforms by Groundwater Outflow In LaFleur R G ed Groundwater as a Geologic Agent Boston MA Allen and Unwin pp 18 58 a b Nash D J 1996 Groundwater Sapping and Valley Development in the Hackness Hills North Yorkshire England Earth Surface Processes and Landforms 9 ed 21 9 781 795 Bibcode 1996ESPL 21 781N doi 10 1002 sici 1096 9837 199609 21 9 lt 781 aid esp616 gt 3 0 co 2 o Lamb M P Dietrich W E Aciego S M Depaolo D J Manga M 2008 Formation of Box Canyon Idaho by Megaflood Implications for Seepage Erosion on Earth and Mars PDF Science 320 5879 1067 1070 Bibcode 2008Sci 320 1067L doi 10 1126 science 1156630 PMID 18497296 S2CID 30609556 a b c d Rosenberry Donald University of Colorado Ground water Sapping and the Generation of Natural Ampitheaters a b Kochel R C Piper J F 1986 Morphology of Large Valleys on Hawaii Evidence for Groundwater Sapping and Comparisons with Martian Valleys Journal of Geophysical Research 91 B13 175 192 Bibcode 1986JGR 91E 175K doi 10 1029 jb091ib13p0e175 Gulick V C 2001 Origin of the Valley Networks on Mars a Hydrological Perspective Geomorphology 37 3 4 241 268 Bibcode 2001Geomo 37 241G doi 10 1016 s0169 555x 00 00086 6 hdl 2060 20000092094 External links EditSimulation of Groundwater Sapping Alan D Howard Introduction Groundwater Sapping on Mars and Earth in Sapping Features of the Colorado Plateau edited by A D Howard R C Kochel and H R Holt NASA SP 491 p 1 5 1988 Julie E Laity and Michael C Malin Sapping processes and the development of theater headed valley networks on the Colorado Plateau Geological Society of America Bulletin Vol 96 No 2 1985 pp 203 217 Abstract Stepinski T F Coradetti S 2004 Comparing morphologies of drainage basins on Mars and Earth using integral geometry and neural maps Geophysical Research Letters 31 15 L15604 Bibcode 2004GeoRL 3115604S doi 10 1029 2004GL020359 Lou W 2000 Quantifying Groundwater sapping Landforms with a Hyposemetric Technique Journal of Geophysical Research 105 1 1685 1694 Bibcode 2000JGR 105 1685L doi 10 1029 1999je001096 Retrieved from https en wikipedia org w index php title Groundwater sapping amp oldid 1171078845, wikipedia, wiki, book, books, library,
