Mass wasting explained

Mass wasting, also known as mass movement,[1] is a general term for the movement of rock or soil down slopes under the force of gravity. It differs from other processes of erosion in that the debris transported by mass wasting is not entrained in a moving medium, such as water, wind, or ice. Types of mass wasting include creep, solifluction, rockfalls, debris flows, and landslides, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years. Mass wasting occurs on both terrestrial and submarine slopes, and has been observed on Earth, Mars, Venus, Jupiter's moon Io, and on many other bodies in the Solar System.

Subsidence is sometimes regarded as a form of mass wasting. A distinction is then made between mass wasting by subsidence, which involves little horizontal movement, and mass wasting by slope movement.

Rapid mass wasting events, such as landslides, can be deadly and destructive. More gradual mass wasting, such as soil creep, poses challenges to civil engineering, as creep can deform roadways and structures and break pipelines. Mitigation methods include slope stabilization, construction of walls, catchment dams, or other structures to contain rockfall or debris flows, afforestation, or improved drainage of source areas.

Types

Mass wasting is a general term for any process of erosion that is driven by gravity and in which the transported soil and rock is not entrained in a moving medium, such as water, wind, or ice.[2] The presence of water usually aids mass wasting, but the water is not abundant enough to be regarded as a transporting medium. Thus, the distinction between mass wasting and stream erosion lies between a mudflow (mass wasting) and a very muddy stream (stream erosion), without a sharp dividing line.[3] Many forms of mass wasting are recognized, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years.[2]

Based on how the soil, regolith or rock moves downslope as a whole, mass movements can be broadly classified as either creeps or landslides.[4] Subsidence is sometimes also regarded as a form of mass wasting.[5] A distinction is then made between mass wasting by subsidence, which involves little horizontal movement, and mass wasting by slope movement.[6]

Creep

Soil creep is a slow and long term mass movement. The combination of small movements of soil or rock in different directions over time is directed by gravity gradually downslope. The steeper the slope, the faster the creep. The creep makes trees and shrubs curve to maintain their perpendicularity, and they can trigger landslides if they lose their root footing. The surface soil can migrate under the influence of cycles of freezing and thawing, or hot and cold temperatures, inching its way towards the bottom of the slope forming terracettes. Landslides are often preceded by soil creep accompanied with soil sloughing—loose soil that falls and accumulates at the base of the steepest creep sections.[7]

Solifluction

See main article: Solifluction. Solifluction is a form of creep characteristics of arctic or alpine climates. It takes place in soil saturated with moisture that thaws during the summer months to creep downhill. It takes place on moderate slopes, relatively free of vegetation, that are underlain by permafrost and receive a constant supply of new debris by weathering. Solifluction affects the entire slope rather than being confined to channels and can produce terrace-like landforms or stone rivers.

Landslide

See main article: Landslide. A landslide, also called a landslip, is a relatively rapid movement of a large mass of earth and rocks down a hill or a mountainside. Landslides can be further classified by the importance of water in the mass wasting process. In a narrow sense, landslides are rapid movement of large amounts of relatively dry debris down moderate to steep slopes. With increasing water content, the mass wasting takes the form of debris avalanches, then earthflows, then mudflows. Further increase in water content produces a sheetflood, which is a form of sheet erosion rather than mass wasting.

Occurrences

On Earth, mass wasting occurs on both terrestrial and submarine slopes.[8] Submarine mass wasting is particularly common along glaciated coastlines where glaciers are retreating and great quantities of sediments are being released. Submarine slides can transport huge volumes of sediments for hundreds of kilometers in a few hours.[9]

Mass wasting is a common phenomenon throughout the Solar System, occurring where volatile materials are lost from a regolith. Such mass wasting has been observed on Mars, Io, Triton, and possibly Europa and Ganymede.[10] Mass wasting also occurs in the equatorial regions of Mars, where stopes of soft sulfate-rich sediments are steepened by wind erosion.[11] Mass wasting on Venus is associated with the rugged terrain of tesserae.[12] Io shows extensive mass wasting of its volcanic mountains.[13]

Deposits and landforms

Mass wasting affects geomorphology, most often in subtle, small-scale ways, but occasionally more spectacularly.

Soil creep is rarely apparent but can produce such subtle effects as curved forest growth and tilted fences and telephone poles. It occasionally produces low scarps and shallow depressions. Solifluction produced lobed or sheetlike deposits, with fairly definite edges, in which clasts (rock fragments) are oriented perpendicular to the contours of the deposit.[14]

Rockfall can produce talus slopes at the feet of cliffs. A more dramatic manifestation of rockfall is rock glaciers, which form from rockfall from cliffs oversteepened by glaciers.

Landslides can produce scarps and step-like small terraces. Landslide deposits are poorly sorted. Those rich in clay may show stretched clay lumps (a phenomenon called boudinage) and zones of concentrated shear.[14]

Debris flow deposits take the form of long, narrow tracks of very poorly sorted material. These may have natural levees at the sides of the tracks, and sometimes consist of lenses of rock fragments alternating with lenses of fine-grained earthy material.[14] Debris flows often form much of the upper slopes of alluvial fans.[15]

Causes

Triggers for mass wasting can be divided into passive and activating (initiating) causes. Passive causes include:

Activating causes include:

Hazards and mitigation

Mass wasting causes problems for civil engineering, particularly highway construction. It can displace roads, buildings, and other construction and can break pipelines. Historically, mitigation of landslide hazards on the Gaillard Cut of the Panama Canal accounted for 73062600order=flipNaNorder=flip of the 168265924order=flipNaNorder=flip of material removed while excavating the cut.

Rockslides or landslides can have disastrous consequences, both immediate and delayed. The Oso disaster of March 2014 was a landslide that caused 43 fatalities in Oso, Washington, US.[17] Delayed consequences of landslides can arise from the formation of landslide dams, as at Thistle, Utah, in April 1983.[18] [19]

Volcano flanks can become over-steep resulting in instability and mass wasting. This is now a recognised part of the growth of all active volcanoes.[20] It is seen on submarine volcanoes as well as surface volcanoes:[21] Kamaʻehuakanaloa (formerly Loihi) in the Hawaiian–Emperor seamount chain[22] and Kick 'em Jenny in the Lesser Antilles Volcanic Arc[23] are two submarine volcanoes that are known to undergo mass wasting. The failure of the northern flank of Mount St. Helens in 1980 showed how rapidly volcanic flanks can deform and fail.[24]

Methods of mitigation of mass wasting hazards include:

See also

Further reading

External links

Notes and References

  1. Book: Allaby . Michael . A dictionary of geology and earth sciences . 2013 . Oxford University Press . Oxford . 9780199653065 . Fourth . mass movement.
  2. Book: Jackson . Julia A. . Glossary of geology. . 1997 . American Geological Institute . Alexandria, Virginia . 0922152349 . Fourth . Mass wasting.
  3. Book: Thornbury . William D. . Principles of geomorphology . 1969 . Wiley . New York . 0471861979 . 36 . 2d.
  4. Book: Allaby . Michael . A dictionary of geology and earth sciences . 2013 . Oxford University Press . Oxford . 9780199653065 . Fourth . mass-wasting.
  5. http://www.britannica.com/EBchecked/topic/368257/mass-movement Britannica
  6. Fleming . Robert W. . Varnes . David J. . Slope movements . The Heritage of Engineering Geology; the First Hundred Years . 1991 . 201–218 . 10.1130/DNAG-CENT-v3.201. 0813753031 .
  7. Web site: Indicators of potentially unstable slopes . 2019-01-22 . Sound Native Plants.
  8. Book: Yamada . Yasuhiro . Kawamura . Kiichiro . Ikehara . Ken . Ogawa . Yujiro . Urgeles . Roger . Mosher . David . Chaytor . Jason . Strasser . Michael . Submarine Mass Movements and Their Consequences . 2012 . 1–12 . 10.1007/978-94-007-2162-3_1. 978-94-007-2161-6 .
  9. Elverhøi . Anders . de Blasio . Fabio V. . Butt . Faisal A. . Issler . Dieter . Harbitz . Carl . Engvik . Lars . Solheim . Anders . Marr . Jeffrey . Submarine mass-wasting on glacially-influenced continental slopes: processes and dynamics . Geological Society, London, Special Publications . 2002 . 203 . 1 . 73–87 . 10.1144/GSL.SP.2002.203.01.05. 2002GSLSP.203...73E . 129761985 .
  10. Moore . Jeffrey M. . Mellon . Michael T. . Zent . Aaron P. . Mass Wasting and Ground Collapse in Terrains of Volatile-Rich Deposits as a Solar System-Wide Geological Process: The Pre-Galileo View . Icarus . July 1996 . 122 . 1 . 63–78 . 10.1006/icar.1996.0109. 1996Icar..122...63M .
  11. Thomas . M.F. . McEwen . A.S. . Dundas . C.M. . Present-day mass wasting in sulfate-rich sediments in the equatorial regions of Mars . Icarus . May 2020 . 342 . 113566 . 10.1016/j.icarus.2019.113566. 2020Icar..34213566T . 213058440 .
  12. Bindschadler . D. L. . Head . J. W. . Diffuse scattering of radar on the surface of Venus: Origin and implications for the distribution of soils . Earth, Moon, and Planets . August 1988 . 42 . 2 . 133–149 . 10.1007/BF00054542. 1988EM&P...42..133B . 120272183 .
  13. Turtle . Elizabeth P. . Keszthelyi . Laszlo P. . McEwen . Alfred S. . Radebaugh . Jani . Milazzo . Moses . Simonelli . Damon P. . Geissler . Paul . Williams . David A. . Perry . Jason . Jaeger . Windy L. . The final Galileo SSI observations of Io: orbits G28-I33 . Icarus . May 2004 . 169 . 1 . 3–28 . 10.1016/j.icarus.2003.10.014. 2004Icar..169....3T .
  14. Mücher . Herman . van Steijn . Henk . Kwaad . Frans . Colluvial and Mass Wasting Deposits . Interpretation of Micromorphological Features of Soils and Regoliths . 2018 . 21–36 . 10.1016/B978-0-444-63522-8.00002-4. 9780444635228 .
  15. Book: Blatt . Harvey . Middletone . Gerard . Murray . Raymond . Origin of sedimentary rocks . 1980 . Prentice-Hall . Englewood Cliffs, N.J. . 0136427103 . 631 . 2d.
  16. Parker . Robert N. . Densmore . Alexander L. . Rosser . Nicholas J. . de Michele . Marcello . Li . Yong . Huang . Runqiu . Whadcoat . Siobhan . Petley . David N. . Mass wasting triggered by the 2008 Wenchuan earthquake is greater than orogenic growth . Nature Geoscience . July 2011 . 4 . 7 . 449–452 . 10.1038/ngeo1154. 2011NatGe...4..449P . 140541040 .
  17. Iverson . R.M. . George . D.L. . Allstadt . K. . Kate Allstadt . Reid . M.E. . Collins . B.D. . Vallance . J.W. . Schilling . S.P. . Godt . J.W. . Cannon . C.M. . Magirl . C.S. . Baum . R.L. . Coe . J.A. . Schulz . W.H. . Bower . J.B. . February 2015 . Landslide mobility and hazards: implications of the 2014 Oso disaster . Earth and Planetary Science Letters . 412 . 197–208 . 2015E&PSL.412..197I . 10.1016/j.epsl.2014.12.020 . free.
  18. Book: Schuster . Robert L. . Landslide dams : processes, risk and mitigation : proceedings of a session . 1986 . ASCE . New York, N.Y. . 978-0-87262-524-2.
  19. Thistle Landslide Revisited, Utah County, Utah. Milligan. Mark. Survey Notes. 37. 2. May 2005. October 28, 2009.
  20. Moon . Vicki . Simpson . Christine J . Large-scale mass wasting in ancient volcanic materials . Engineering Geology . April 2002 . 64 . 1 . 41–64 . 10.1016/S0013-7952(01)00092-8. 2002EngGe..64...41M .
  21. Hildenbrand . A. . Marques . F. O. . Catalão . J. . Large-scale mass wasting on small volcanic islands revealed by the study of Flores Island (Azores) . Scientific Reports . December 2018 . 8 . 1 . 13898 . 10.1038/s41598-018-32253-0. 30224744 . 6141455 . 2018NatSR...813898H .
  22. Fornari . Daniel J. . Garcia . Michael O. . Tyce . Robert C. . Gallo . David G. . Morphology and structure of Loihi Seamount based on Seabeam Sonar Mapping . Journal of Geophysical Research: Solid Earth . 10 December 1988 . 93 . B12 . 15227–15238 . 10.1029/JB093iB12p15227. 1988JGR....9315227F .
  23. Carey . Steven . Ballard . Robert . Bell . Katherine L.C. . Bell . Richard J. . Connally . Patrick . Dondin . Frederic . Fuller . Sarah . Gobin . Judith . Miloslavich . Patricia . Phillips . Brennan . Roman . Chris . Seibel . Brad . Siu . Nam . Smart . Clara . Cold seeps associated with a submarine debris avalanche deposit at Kick'em Jenny volcano, Grenada (Lesser Antilles) . Deep Sea Research Part I: Oceanographic Research Papers . November 2014 . 93 . 156–160 . 10.1016/j.dsr.2014.08.002. 2014DSRI...93..156C .
  24. Glicken . Harry . 1996 . Rockslide-debris Avalanche of May 18, 1980, Mount St. Helens Volcano, Washington . U.S. Geological Survey Open-File Report . Open-File Report . 96-677 . 10.3133/ofr96677 . 25 November 2021. free .
  25. Book: van Beek . Rens . Cammeraat . Erik . Andreu . Vicente . Mickovski . Slobodan B. . Dorren . Luuk . Slope Stability and Erosion Control: Ecotechnological Solutions . Hillslope Processes: Mass Wasting, Slope Stability and Erosion . 2008 . 17–64 . 10.1007/978-1-4020-6676-4_3. 978-1-4020-6675-7 .
  26. Adu-Boahen . K. . Dadson . I.Y. . Yike . P . 2020 . Geomorphic Assessment of Residence Knowledge of Mass Wasting in the Weija Catchment of Ghana . ADRRI Journal (Multidisciplinary) . 29 . 1(6) . 89–112 . 26 November 2021.
  27. Book: De Blasio . Fabio Vittorio . Introduction to the physics of landslides : lecture notes on the dynamics of mass wasting . 2011 . Dordrecht . 9789400711228 . 280.
  28. Mulyono. A. Subardja. A. Ekasari. I. Lailati. M. Sudirja. R. Ningrum. W. February 2018. The Hydromechanics of Vegetation for Slope Stabilization. IOP Conference Series: Earth and Environmental Science. 118. 1. 012038. 10.1088/1755-1315/118/1/012038. 2018E&ES..118a2038M. 134151880. 1755-1307. free.

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