View source for Landslide

{{Short description|Natural hazard involving ground movement}}
{{About|the geological phenomenon}}
[[File:Landslide in Cusco, Peru - 2018.jpg|thumb|right|A landslide near [[Cusco, Peru]], in 2018]]
[[File:NASA Model Finds Landslide Threats in Near Real-Time During Heavy Rains.webm|thumb|A NASA model has been developed to look at how potential landslide activity is changing around the world.]]
[[File:Landslide_animation_San_Matteo_County.gif|thumb|Animation of a landslide in [[San Mateo County, California]]]]
[[File:Landslips.jpg|thumb|Landslips]]
[[File:Erosion de la riviere Sainte-Anne.jpg|thumb|[[Noire River (Sainte-Anne River tributary)|Noire River]] (Rivière Noire), [[Saint-Alban, Quebec|Saint-Alban]] landslide 1894, [[Quebec]], Canada<ref name="Annual report of the Quebec Bureau of Mines">{{cite web |author1= J. W. Laverdière, Abbé |title=Annual report of the Quebec Bureau of Mines |url=https://gq.mines.gouv.qc.ca/documents/examine/RASM1936D2(A)/RASM1936D2(A).pdf |website=Gouvernement of Quebec |publisher=Ministry of Natural Resources and Forests |access-date=3 November 2024 |page=33 |date=1936 |quote=The country in the vicinity of Sainte-Anne-de-la-Pérade, and stretching east and west of the Sainte-Anne river, is a clay plain, well suited for agriculture.}}</ref><ref name="Hydrological and multi-resource portrait of the Sainte-Anne River watershed.">{{cite web |author1=Bitzakidis, Stéfanos |author2=S. Gagné |author3=D. Genois |author4=C. Paradis |title=Hydrological and multi-resource portrait of the Sainte-Anne River watershed. |url=https://www.capsa-org.com/uploads/documents/BibliEAUtheque/Rapport-CAPSA/Portrait_hydrologique_et_multiressources_du_BV_Ste_Anne.pdf |publisher=CAPSA - Corporation d'aménagement et de protection de la Sainte-Anne |access-date=5 November 2024 |pages=19 of 237 |language=fr |date=April 2003 |quote=The river became larger and shallower, and the enormous amount of soil carried away (equivalent to natural contributions over a period of 5,000 years) began to settle 4 km upstream from the mouth to the St. Lawrence River.}}</ref>]]
'''Landslides''', also known as '''landslips''', '''rockslips''' or '''rockslides''',<ref>{{cite web|url=http://www.thesaurus.com/browse/landslide|title=Landslide synonyms|year=2013|series=Roget's 21st Century Thesaurus|website=thesaurus.com|access-date=16 March 2018|archive-date=24 September 2020|archive-url=https://web.archive.org/web/20200924234434/https://www.thesaurus.com/browse/landslide|url-status=live}}</ref><ref>McGraw-Hill Encyclopedia of Science & Technology, 11th Edition, {{ISBN|9780071778343}}, 2012</ref><ref>{{cite web|url=https://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html|title=USGS factsheet, Landslide Types and Processes, 2004.|access-date=2020-08-28|archive-date=2020-10-04|archive-url=https://web.archive.org/web/20201004122221/https://pubs.usgs.gov/fs/2004/3072/fs-2004-3072.html|url-status=live}}</ref> are several forms of [[mass wasting]] that may include a wide range of ground movements, such as [[rockfall]]s, [[mudflows]], shallow or deep-seated [[slope failure]]s and [[debris flow]]s.<ref name=":4">{{Cite journal|last1=Hungr|first1=Oldrich|last2=Leroueil|first2=Serge|last3=Picarelli|first3=Luciano|date=2014-04-01|title=The Varnes classification of landslide types, an update|journal=Landslides|language=en|volume=11|issue=2|pages=167–194|doi=10.1007/s10346-013-0436-y|bibcode=2014Lands..11..167H |s2cid=38328696|issn=1612-5118}}</ref> Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from [[mountain]] ranges to [[coast]]al [[cliff]]s or even underwater,<ref>{{Cite journal|last1=Haflidason|first1=Haflidi|last2=Sejrup|first2=Hans Petter|last3=Nygård|first3=Atle|last4=Mienert|first4=Jurgen|last5=Bryn|first5=Petter|last6=Lien|first6=Reidar|last7=Forsberg|first7=Carl Fredrik|last8=Berg|first8=Kjell|last9=Masson|first9=Doug|date=2004-12-15|title=The Storegga Slide: architecture, geometry and slide development|url=https://www.sciencedirect.com/science/article/pii/S0025322704002713|journal=Marine Geology|series=COSTA - Continental Slope Stability|language=en|volume=213|issue=1|pages=201–234|doi=10.1016/j.margeo.2004.10.007|bibcode=2004MGeol.213..201H|issn=0025-3227|url-access=subscription}}</ref> in which case they are called [[submarine landslides]].

[[Gravity]] is the primary driving force for a landslide to occur, but there are other factors affecting [[slope stability]] that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event (such as heavy [[rain]]fall, an [[earthquake]], a slope cut to build a road, and many others), although this is not always identifiable.

Landslides are frequently made worse by human development (such as [[urban sprawl]]) and resource exploitation (such as [[mining]] and [[deforestation]]). [[Land degradation]] frequently leads to less stabilization of soil by [[vegetation]].<ref name=":6" /> Additionally, global warming caused by [[climate change]] and other [[human impact on the environment]], can increase the frequency of natural events (such as [[extreme weather]]) which trigger landslides.<ref>{{Cite web |last=Merzdorf |first=Jessica |title=Climate Change Could Trigger More Landslides in High Mountain Asia |url=https://climate.nasa.gov/news/2951/climate-change-could-trigger-more-landslides-in-high-mountain-asia |access-date=2023-02-04 |website=Climate Change: Vital Signs of the Planet |publisher=NASA's Goddard Space Flight Center |archive-date=2023-02-04 |archive-url=https://web.archive.org/web/20230204130959/https://climate.nasa.gov/news/2951/climate-change-could-trigger-more-landslides-in-high-mountain-asia/ |url-status=live }}</ref> [[Landslide mitigation]] describes the policy and practices for reducing the risk of human impacts of landslides, reducing the risk of [[natural disaster]].

==Causes==
{{Main|Causes of landslides}}
[[Image:Mameyes.jpg|thumb|[[1985 Puerto Rico floods|The Mameyes Landslide]], in the Mameyes [[neighborhood]] of barrio [[Portugués Urbano]] in [[Ponce, Puerto Rico]], was caused by extensive accumulation of rains and, according to some sources, lightning. It buried more than 100 homes.]]
[[File:Landslide in Sweden (Surte) 1950, 2.jpg|thumb|The landslide at [[Surte]] in Sweden, 1950. It was a [[quick clay]] slide that killed one person.]]

Landslides occur when the slope (or a portion of it) undergoes some processes that change its condition from stable to unstable. This is essentially due to a decrease in the [[Shear strength (soil)|shear strength]] of the slope material, an increase in the [[shear stress]] borne by the material, or a combination of the two. A change in the stability of a slope can be caused by a number of factors, acting together or alone. Natural causes of landslides include:
* increase in water content (loss of suction) or saturation by rain water infiltration, snow melting, or [[glacier]]s melting;<ref>{{Cite journal|last1=Subramanian|first1=S. Siva|last2=Fan|first2=X.|last3=Yunus|first3=A. P.|last4=Asch|first4=T. van|last5=Scaringi|first5=G.|last6=Xu|first6=Q.|last7=Dai|first7=L.|last8=Ishikawa|first8=T.|last9=Huang|first9=R.|year=2020|title=A Sequentially Coupled Catchment-Scale Numerical Model for Snowmelt-Induced Soil Slope Instabilities|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JF005468|journal=Journal of Geophysical Research: Earth Surface|language=en|volume=125|issue=5|article-number=e2019JF005468|doi=10.1029/2019JF005468|bibcode=2020JGRF..12505468S|s2cid=218825257|issn=2169-9011|access-date=2021-02-23|archive-date=2022-03-06|archive-url=https://web.archive.org/web/20220306044629/https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JF005468|url-status=live|url-access=subscription}}</ref>
*rising of [[groundwater]] and increase of pore water pressure (e.g. due to [[aquifer]] recharge in rainy seasons, or by rain water infiltration);<ref name=":2">{{Cite journal|last1=Hu|first1=Wei|last2=Scaringi|first2=Gianvito|last3=Xu|first3=Qiang|last4=Van Asch|first4=Theo W. J.|date=2018-04-10|title=Suction and rate-dependent behaviour of a shear-zone soil from a landslide in a gently-inclined mudstone-sandstone sequence in the Sichuan basin, China|journal=Engineering Geology|language=en|volume=237|pages=1–11|doi=10.1016/j.enggeo.2018.02.005|bibcode=2018EngGe.237....1H |issn=0013-7952}}</ref>
*increase of hydrostatic pressure in cracks and fractures;<ref name=":2" /><ref name=":3">{{Cite journal|last1=Fan|first1=Xuanmei|last2=Xu|first2=Qiang|last3=Scaringi|first3=Gianvito|date=2017-12-01|title=Failure mechanism and kinematics of the deadly June 24th 2017 Xinmo landslide, Maoxian, Sichuan, China|journal=Landslides|language=en|volume=14|issue=6|pages=2129–2146|doi=10.1007/s10346-017-0907-7|bibcode=2017Lands..14.2129F |s2cid=133681894|issn=1612-5118}}</ref>
* loss or absence of vertical vegetative structure, [[soil nutrients]], and [[soil structure]] (e.g. after a wildfire);<ref>{{Cite journal|last1=Rengers|first1=Francis K.|last2=McGuire|first2=Luke A.|last3=Oakley|first3=Nina S.|last4=Kean|first4=Jason W.|last5=Staley|first5=Dennis M.|last6=Tang|first6=Hui|date=2020-11-01|title=Landslides after wildfire: initiation, magnitude, and mobility|journal=Landslides|language=en|volume=17|issue=11|pages=2631–2641|doi=10.1007/s10346-020-01506-3|s2cid=221110680|issn=1612-5118|doi-access=free|bibcode=2020Lands..17.2631R }}</ref>
*[[erosion]] of the top of a slope by rivers or sea [[wave]]s;<ref>{{Cite journal|last1=Edil|first1=T. B.|last2=Vallejo|first2=L. E.|date=1980-07-01|title=Mechanics of coastal landslides and the influence of slope parameters|journal=Engineering Geology|series=Special Issue Mechanics of Landslides and Slope Stability|language=en|volume=16|issue=1|pages=83–96|doi=10.1016/0013-7952(80)90009-5|bibcode=1980EngGe..16...83E |issn=0013-7952}}</ref>
*physical and chemical [[weathering]] (e.g. by repeated freezing and thawing, heating and cooling, salt leaking in the groundwater or mineral dissolution);<ref name=":0" /><ref name=":1" /><ref>{{Cite journal|last1=Fan|first1=Xuanmei|last2=Xu|first2=Qiang|last3=Scaringi|first3=Gianvito|last4=Li|first4=Shu|last5=Peng|first5=Dalei|date=2017-10-13|title=A chemo-mechanical insight into the failure mechanism of frequently occurred landslides in the Loess Plateau, Gansu Province, China|url=https://www.sciencedirect.com/science/article/pii/S001379521730889X|journal=Engineering Geology|language=en|volume=228|pages=337–345|doi=10.1016/j.enggeo.2017.09.003|bibcode=2017EngGe.228..337F |issn=0013-7952|url-access=subscription}}</ref>
* ground shaking caused by [[earthquake]]s, which can destabilize the slope directly (e.g., by inducing [[soil liquefaction]]) or weaken the material and cause movement that will eventually produce a landslide;<ref name=":3" /><ref>{{Cite journal|last1=Fan|first1=Xuanmei|last2=Scaringi|first2=Gianvito|last3=Domènech|first3=Guillem|last4=Yang|first4=Fan|last5=Guo|first5=Xiaojun|last6=Dai|first6=Lanxin|last7=He|first7=Chaoyang|last8=Xu|first8=Qiang|last9=Huang|first9=Runqiu|date=2019-01-09|title=Two multi-temporal datasets that track the enhanced landsliding after the 2008 Wenchuan earthquake |bibcode-access=free |url=https://www.earth-syst-sci-data.net/11/35/2019/essd-11-35-2019.html|journal=Earth System Science Data|language=en|volume=11|issue=1|pages=35–55|doi=10.5194/essd-11-35-2019|issn=1866-3508|bibcode=2019ESSD...11...35F|doi-access=free|access-date=2019-01-09|archive-date=2020-03-04|archive-url=https://web.archive.org/web/20200304105948/https://www.earth-syst-sci-data.net/11/35/2019/essd-11-35-2019.html|url-status=live}}</ref><ref>{{Cite journal|last1=Fan|first1=Xuanmei|last2=Xu|first2=Qiang|last3=Scaringi|first3=Gianvito|date=2018-01-26|title=Brief communication: Post-seismic landslides, the tough lesson of a catastrophe |bibcode-access=free |journal=Natural Hazards and Earth System Sciences|language=en|volume=18|issue=1|pages=397–403|doi=10.5194/nhess-18-397-2018|issn=1561-8633|bibcode=2018NHESS..18..397F|doi-access=free}}</ref>
* [[volcano|volcanic eruptions]];<ref>{{Cite journal|last1=Watt |first1=Sebastian F.L.|last2=Talling |first2=Peter J.|last3=Hunt |first3=James E. |s2cid-access=free |year=2014|title=New Insights into the Emplacement Dynamics of Volcanic Island Landslides|journal=Oceanography|volume=27|issue=2|pages=46–57|doi=10.5670/oceanog.2014.39|jstor=24862154|s2cid=55516702|issn=1042-8275|doi-access=free|bibcode=2014Ocgpy..27b..46W }}</ref>
* changes in pore fluid composition;<ref>{{Cite journal |last1=Di Maio |first1=C. |last2=Scaringi |first2=G. |date=2016-01-18 |title=Shear displacements induced by decrease in pore solution concentration on a pre-existing slip surface |url=https://www.sciencedirect.com/science/article/pii/S0013795215300922 |journal=Engineering Geology |language=en |volume=200 |pages=1–9 |doi=10.1016/j.enggeo.2015.11.007 |bibcode=2016EngGe.200....1D |issn=0013-7952|url-access=subscription }}</ref>
* changes in temperature (seasonal or induced by climate change).<ref>{{Cite journal |last1=Scaringi |first1=Gianvito |last2=Loche |first2=Marco |date=2022-03-15 |title=A thermo-hydro-mechanical approach to soil slope stability under climate change |journal=Geomorphology |language=en |volume=401 |article-number=108108 |doi=10.1016/j.geomorph.2022.108108 |bibcode=2022Geomo.40108108S |s2cid=245941223 |issn=0169-555X|doi-access=free }}</ref><ref>{{Cite journal |last1=Shibasaki |first1=Tatsuya |last2=Matsuura |first2=Sumio |last3=Okamoto |first3=Takashi |date=2016-07-16 |title=Experimental evidence for shallow, slow-moving landslides activated by a decrease in ground temperature: Landslides Affected by Ground Temperature |url=http://doi.wiley.com/10.1002/2016GL069604 |journal=Geophysical Research Letters |language=en |volume=43 |issue=13 |pages=6975–6984 |doi=10.1002/2016GL069604|s2cid=132940118 |url-access=subscription }}</ref>

Landslides are aggravated by human activities, such as:
* [[deforestation]], [[Tillage|cultivation]] and [[construction]];
* [[oscillation|vibrations]] from [[machinery]] or [[traffic]];<ref>{{Cite journal|last=Laimer|first=Hans Jörg|date=2017-05-18|title=Anthropogenically induced landslides – A challenge for railway infrastructure in mountainous regions|url=https://www.sciencedirect.com/science/article/pii/S0013795216307335|journal=Engineering Geology|language=en|volume=222|pages=92–101|doi=10.1016/j.enggeo.2017.03.015|bibcode=2017EngGe.222...92L |issn=0013-7952|url-access=subscription}}</ref>
* [[Explosive material|blasting]] and [[mining]];<ref>{{Cite journal|last1=Fan|first1=Xuanmei|last2=Xu|first2=Qiang|last3=Scaringi|first3=Gianvito|date=2018-10-24|title=The "long" runout rock avalanche in Pusa, China, on 28 August 2017: a preliminary report|journal=Landslides|language=en|volume=16|pages=139–154|doi=10.1007/s10346-018-1084-z|s2cid=133852769|issn=1612-5118}}</ref>
* [[Earthworks (engineering)|earthwork]] (e.g. by altering the shape of a slope, or imposing new loads);
* in shallow [[soil]]s, the removal of deep-[[root]]ed [[vegetation]] that binds [[colluvium]] to [[bedrock]];
* agricultural or forestry activities ([[logging]]), and [[urbanization]], which change the amount of water infiltrating the soil.
*temporal variation in [[land use]] and [[land cover]] (LULC): it includes the human abandonment of farming areas, e.g. due to the economic and social transformations which occurred in Europe after the Second World War. [[Land degradation]] and extreme rainfall can increase the frequency of [[soil erosion|erosion]] and landslide phenomena.<ref name=":6">{{cite journal | title = Investigation on Farmland Abandonment of Terraced Slopes Using Multitemporal Data Sources Comparison and Its Implication on Hydro-Geomorphological Processes | author = Giacomo Pepe | author2 = Andrea Mandarino | author3 = Emanuele Raso | author4 = Patrizio Scarpellini | author5 = Pierluigi Brandolini | author6 = Andrea Cevasco | journal = [[Water (journal)|Water]] | year = 2019 | oclc = 	8206777258 | issue = 11 | volume = 8 | page = 1552 | doi = 10.3390/w11081552 | publisher = [[MDPI]] | issn = 2073-4441 | doi-access = free | bibcode = 2019Water..11.1552P | hdl = 11567/968956 | hdl-access = free }}, at the introductory section.</ref>

==Types==
{{Main|Landslide classification}}
[[File:Major types of landslide movement.jpg|thumb|upright=1.85|Types of landslide]]

===Hungr-Leroueil-Picarelli classification===

In traditional usage, the term landslide has at one time or another been used to cover almost all forms of [[mass movement (geology)|mass movement]] of rocks and [[regolith]] at the Earth's surface. In 1978, geologist David Varnes noted this imprecise usage and proposed a new, much tighter scheme for the classification of mass movements and [[subsidence]] processes.<ref name="Varnes">Varnes D. J., Slope movement types and processes. In: Schuster R. L. & Krizek R. J. Ed., Landslides, analysis and control. Transportation Research Board Sp. Rep. No. 176, Nat. Acad. oi Sciences, pp. 11–33, 1978.</ref> This scheme was later modified by Cruden and Varnes in 1996,<ref name='CrudenVarnes'>Cruden, David M., and David J. Varnes. "Landslides: investigation and mitigation. Chapter 3-Landslide types and processes." Transportation research board special report 247 (1996).</ref> and refined by Hutchinson (1988),<ref name='Hutchinson'>Hutchinson, J. N. "General report: morphological and geotechnical parameters of landslides in relation to geology and hydrogeology." International symposium on landslides. 5. 1988.</ref> Hungr et al. (2001),<ref name="Hungr">Hungr O, Evans SG, Bovis M, and Hutchinson JN (2001) Review of the classification of landslides of the flow type. Environmental and Engineering Geoscience VII, 221–238.</ref> and finally by Hungr, Leroueil and Picarelli (2014).<ref name=":4" /> The classification resulting from the latest update is provided below.
{| class="wikitable"
|+
!Type of movement
!Rock
!Soil
|-
|Fall
|''Rock/ice'' fall
|''Boulder/debris/silt'' fall
|-
| rowspan="2" |Topple
|Rock block topple
| rowspan="2" |''Gravel/sand/silt'' topple
|-
|Rock flexural topple
|-
| rowspan="5" |Slide
|Rock rotational slide
|''Clay/silt'' rotational slide
|-
|Rock planar slide
|''Clay/silt'' planar slide
|-
|Rock wedge slide
|''Gravel/sand/debris'' slide
|-
|Rock compound slide
| rowspan="2" |''Clay/silt'' compound slide
|-
|Rock irregular slide
|-
| rowspan="2" |Spread
| rowspan="2" |Rock slope spread
|''Sand/silt'' liquefaction spread
|-
|Sensitive clay spread
|-
| rowspan="9" |Flow
| rowspan="9" |''Rock/ice'' avalanche
|''Sand/silt/debris'' dry flow
|-
|''Sand/silt/debris'' flowslide
|-
|Sensitive clay flowslide
|-
|Debris flow
|-
|Mud flow
|-
|Debris flood
|-
|Debris avalanche
|-
|Earthflow
|-
|Peat flow
|-
| rowspan="3" |Slope deformation
|Mountain slope deformation
|Soil slope deformation
|-
| rowspan="2" |Rock slope deformation
|Soil creep
|-
|Solifluction
|-
| colspan="3" |Note: the words in ''italics'' are placeholders. Use only one.
|}
Under this classification, six types of movement are recognized. Each type can be seen both in rock and in soil. A fall is a movement of isolated blocks or chunks of soil in free-fall. The term topple refers to blocks coming away by rotation from a vertical face. A slide is the movement of a body of material that generally remains intact while moving over one or several inclined surfaces or thin layers of material (also called shear zones) in which large deformations are concentrated. Slides are also sub-classified by the form of the surface(s) or shear zone(s) on which movement happens. The planes may be broadly parallel to the surface ("planar slides") or spoon-shaped ("rotational slides"). Slides can occur catastrophically, but movement on the surface can also be gradual and progressive. Spreads are a form of subsidence, in which a layer of material cracks, opens up, and expands laterally. Flows are the movement of fluidised material, which can be both dry or rich in water (such as in mud flows). Flows can move imperceptibly for years, or accelerate rapidly and cause disasters. Slope deformations are slow, distributed movements that can affect entire mountain slopes or portions of it. Some landslides are complex in the sense that they feature different movement types in different portions of the moving body, or they evolve from one movement type to another over time. For example, a landslide can initiate as a rock fall or topple and then, as the blocks disintegrate upon the impact, transform into a debris slide or flow. An avalanching effect can also be present, in which the moving mass entrains additional material along its path.

====Flows====
Slope material that becomes [[Aquifer|saturated]] with water may produce a [[debris flow]] or [[mudflow|mud flow]]. However, also dry debris can exhibit flow-like movement.<ref>{{Cite journal|last=Iverson|first=Richard M.|year=1997|title=The physics of debris flows|journal=Reviews of Geophysics|language=en|volume=35|issue=3|pages=245–296|doi=10.1029/97RG00426|bibcode=1997RvGeo..35..245I|s2cid=15955986|issn=1944-9208|doi-access=free}}</ref> Flowing debris or mud may pick up trees, houses and cars, and block bridges and rivers causing [[flooding]] along its path. This phenomenon is particularly hazardous in [[Alpine climate|alpine]] areas, where narrow gorges and steep valleys are conducive of faster flows. Debris and mud flows may initiate on the slopes or result from the fluidization of landslide material as it gains speed or incorporates further debris and water along its path. River blockages as the flow reaches a main stream can generate temporary dams. As the impoundments fail, a domino effect may be created, with a remarkable growth in the volume of the flowing mass, and in its destructive power.[[File:The Costa della Gaveta earthflow.jpg|thumb|The Costa della Gaveta earthflow in [[Potenza]], Italy. Even though it moves at a rate of just a few millimeters per year<ref name=":0">{{Cite journal|last1=Di Maio|first1=Caterina|last2=Vassallo|first2=Roberto|last3=Scaringi|first3=Gianvito|last4=De Rosa|first4=Jacopo|last5=Pontolillo|first5=Dario Michele|last6=Maria Grimaldi|first6=Giuseppe|date=2017-11-01|title=Monitoring and analysis of an earthflow in tectonized clay shales and study of a remedial intervention by KCl wells|url=https://www.researchgate.net/publication/321348162|journal=Rivista Italiana di Geotecnica|volume=51|issue=3|pages=48–63|doi=10.19199/2017.3.0557-1405.048|access-date=2018-05-26|archive-date=2021-04-03|archive-url=https://web.archive.org/web/20210403113248/https://www.researchgate.net/publication/321348162_Monitoring_and_analysis_of_an_earthflow_in_tectonized_clay_shales_and_study_of_a_remedial_intervention_by_KCl_wells|url-status=live}}</ref> and is hardly visible, this landslide causes progressive damage to the national road, the national highway, a flyover, and several houses that are built on it.]]
[[Image:slide-guerrero1.JPG|thumb|A rock slide in [[Guerrero]], Mexico]]

An [[earthflow]] is the downslope movement of mostly fine-grained material. Earthflows can move at speeds within a very wide range, from as low as 1&nbsp;mm/yr<ref name=":0"/><ref name=":1">{{Cite journal|last1=Di Maio|first1=Caterina|last2=Scaringi|first2=Gianvito|last3=Vassallo|first3=R|date=2014-01-01|title=Residual strength and creep behaviour on the slip surface of specimens of a landslide in marine origin clay shales: influence of pore fluid composition|url=https://www.researchgate.net/publication/271630325|journal=Landslides|volume=12|issue=4|pages=657–667|doi=10.1007/s10346-014-0511-z|s2cid=127489377|access-date=2018-05-26|archive-date=2021-03-30|archive-url=https://web.archive.org/web/20210330131020/https://www.researchgate.net/publication/271630325_Residual_strength_and_creep_behaviour_on_the_slip_surface_of_specimens_of_a_landslide_in_marine_origin_clay_shales_influence_of_pore_fluid_composition|url-status=live}}</ref> to many km/h. Though these are a lot like [[mudflow]]s, overall they are more slow-moving and are covered with solid material carried along by the flow from within. Clay, fine sand and silt, and fine-grained, pyroclastic material are all susceptible to earthflows. These flows are usually controlled by the pore water pressures within the mass, which should be high enough to produce a low shearing resistance. On the slopes, some earthflow may be recognized by their elongated shape, with one or more lobes at their toes. As these lobes spread out, drainage of the mass increases and the margins dry out, lowering the overall velocity of the flow. This process also causes the flow to thicken. Earthflows occur more often during periods of high precipitation, which saturates the ground and builds up water pressures. However, earthflows that keep advancing also during dry seasons are not uncommon. Fissures may develop during the movement of clayey materials, which facilitate the intrusion of water into the moving mass and produce faster responses to precipitation.<ref name="b1">{{cite book|last=Easterbrook|first=Don J.|title=Surface Processes and Landforms|location=[[Upper Saddle River]]|publisher=Prentice-Hall|year=1999|isbn=978-0-13-860958-0}}</ref>

{{anchor|Debris avalanche}}

A rock avalanche, sometimes referred to as [[sturzstrom]], is a large and fast-moving landslide of the flow type. It is rarer than other types of landslides but it is often very destructive. It exhibits typically a long runout, flowing very far over a low-angle, flat, or even slightly uphill terrain. The mechanisms favoring the long runout can be different, but they typically result in the weakening of the sliding mass as the speed increases.<ref>{{Cite journal|last1=Hu|first1=Wei|last2=Scaringi|first2=Gianvito|last3=Xu|first3=Qiang|last4=Huang|first4=Runqiu|date=2018-06-05|title=Internal erosion controls failure and runout of loose granular deposits: Evidence from flume tests and implications for post-seismic slope healing|url=https://www.researchgate.net/publication/325582900|journal=Geophysical Research Letters|volume=45|issue=11|page=5518|bibcode=2018GeoRL..45.5518H|doi=10.1029/2018GL078030|s2cid=135013342|doi-access=free}}</ref><ref>{{Cite journal|last1=Hu|first1=Wei|last2=Xu|first2=Qiang|last3=Wang|first3=Gonghui|last4=Scaringi|first4=Gianvito|last5=McSaveney|first5=Mauri|last6=Hicher|first6=Pierre-Yves|date=2017-10-31|title=Shear Resistance Variations in Experimentally Sheared Mudstone Granules: A Possible Shear-Thinning and Thixotropic Mechanism|url=https://www.researchgate.net/publication/320744311|journal=Geophysical Research Letters|volume=44|issue=21|pages=11,040|bibcode=2017GeoRL..4411040H|doi=10.1002/2017GL075261|s2cid=135078422|doi-access=free}}</ref><ref name=":5">{{Cite journal|last1=Scaringi|first1=Gianvito|last2=Hu|first2=Wei|last3=Xu|first3=Qiang|last4=Huang|first4=Runqiu|date=2017-12-20|title=Shear-Rate-Dependent Behavior of Clayey Bimaterial Interfaces at Landslide Stress Levels|url=https://www.researchgate.net/publication/321961897|journal=Geophysical Research Letters|volume=45|issue=2|page=766|bibcode=2018GeoRL..45..766S|doi=10.1002/2017GL076214|doi-access=free}}</ref> The causes of this weakening are not completely understood. Especially for the largest landslides, it may involve the very quick heating of the shear zone due to friction, which may even cause the water that is present to vaporize and build up a large pressure, producing a sort of hovercraft effect.<ref>{{Cite journal|last1=Deng|first1=Yu|last2=Yan|first2=Shuaixing|last3=Scaringi|first3=Gianvito|last4=Liu|first4=Wei|last5=He|first5=Siming|year=2020|title=An Empirical Power Density-Based Friction Law and Its Implications for Coherent Landslide Mobility|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL087581|journal=Geophysical Research Letters|language=en|volume=47|issue=11|article-number=e2020GL087581|doi=10.1029/2020GL087581|bibcode=2020GeoRL..4787581D|s2cid=219437216|issn=1944-8007|access-date=2021-02-23|archive-date=2022-03-06|archive-url=https://web.archive.org/web/20220306051102/https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020GL087581|url-status=live}}</ref> In some cases, the very high temperature may even cause some of the minerals to melt.<ref>{{Cite journal|last1=Deng|first1=Yu|last2=He|first2=Siming|last3=Scaringi|first3=Gianvito|last4=Lei|first4=Xiaoqin|year=2020|title=Mineralogical Analysis of Selective Melting in Partially Coherent Rockslides: Bridging Solid and Molten Friction|url=https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JB019453|journal=Journal of Geophysical Research: Solid Earth|language=en|volume=125|issue=8|article-number=e2020JB019453|doi=10.1029/2020JB019453|bibcode=2020JGRB..12519453D|s2cid=225509252|issn=2169-9356|access-date=2021-02-23|archive-date=2021-10-12|archive-url=https://web.archive.org/web/20211012104536/https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020JB019453|url-status=live|url-access=subscription}}</ref> During the movement, the rock in the shear zone may also be finely ground, producing a nanometer-size mineral powder that may act as a lubricant, reducing the resistance to motion and promoting larger speeds and longer runouts.<ref>{{Cite journal|last1=Rowe|first1=Christie D.|last2=Lamothe|first2=Kelsey|last3=Rempe|first3=Marieke|last4=Andrews|first4=Mark|last5=Mitchell|first5=Thomas M.|last6=Di Toro|first6=Giulio|last7=White|first7=Joseph Clancy|last8=Aretusini|first8=Stefano|date=2019-01-18|title=Earthquake lubrication and healing explained by amorphous nanosilica|journal=Nature Communications|language=en|volume=10|issue=1|page=320|doi=10.1038/s41467-018-08238-y|issn=2041-1723|pmc=6338773|pmid=30659201|bibcode=2019NatCo..10..320R}}</ref> The weakening mechanisms in large rock avalanches are similar to those occurring in seismic faults.<ref name=":5" />
[[File:Landslide in Peru 2 (1063).jpg|thumb|Landslide in Peru after flash flooding in 2013.]]

==== Slides ====
Slides can occur in any rock or soil material and are characterized by the movement of a mass over a planar or curvilinear surface or shear zone.

A debris slide is a type of slide characterized by the chaotic movement of material mixed with water and/or ice. It is usually triggered by the saturation of thickly vegetated slopes which results in an incoherent mixture of broken timber, smaller vegetation and other debris.<ref name="b1" /> Debris flows and avalanches differ from debris slides because their movement is fluid-like and generally much more rapid. This is usually a result of lower shear resistances and steeper slopes. Typically, debris slides start with the detachment of large rock fragments high on the slopes, which break apart as they descend.

Clay and silt slides are usually slow but can experience episodic acceleration in response to heavy rainfall or rapid snowmelt. They are often seen on gentle slopes and move over planar surfaces, such as over the underlying bedrock. Failure surfaces can also form within the clay or silt layer itself, and they usually have concave shapes, resulting in rotational slides.

===Shallow and deep-seated landslides===
[[File:Limone sul Garda Hotel 001.JPG|thumb|Hotel Panorama at [[Lake Garda]]. Part of a hill of [[Devonian]] [[shale]] was removed to make the road, forming a dip-slope. The upper block detached along a bedding plane and is sliding down the hill, forming a jumbled pile of rock at the toe of the slide.]]

Slope failure mechanisms often contain large uncertainties and could be significantly affected by heterogeneity of soil properties.<ref>{{Cite journal |last1=Liu |first1=Xin |last2=Wang |first2=Yu |last3=Li |first3=Dian-Qing |date=2019 |title=Investigation of slope failure mode evolution during large deformation in spatially variable soils by random limit equilibrium and material point methods |url=https://linkinghub.elsevier.com/retrieve/pii/S0266352X19300977 |journal=Computers and Geotechnics |language=en |volume=111 |pages=301–312 |doi=10.1016/j.compgeo.2019.03.022 |bibcode=2019CGeot.111..301L |s2cid=145994705 |access-date=2023-04-10 |archive-date=2022-08-08 |archive-url=https://web.archive.org/web/20220808214316/https://linkinghub.elsevier.com/retrieve/pii/S0266352X19300977 |url-status=live |url-access=subscription }}</ref> A landslide in which the sliding surface is located within the [[soil]] mantle or [[weathering|weathered]] [[bedrock]] (typically to a depth from few decimeters to some meters) is called a shallow landslide. Debris slides and [[debris flow]]s are usually shallow. Shallow landslides can often happen in areas that have slopes with high permeable soils on top of low permeable soils. The low permeable soil traps the water in the shallower soil generating high water pressures. As the top soil is filled with water, it can become unstable and slide downslope.[[File:Kihotown Sehara Miepref No,3.jpg|thumb|Deep-seated landslide on a mountain in Sehara, [[Kihō, Mie|Kihō]], Japan caused by torrential rain of [[Tropical Storm Talas (2011)|Tropical Storm Talas]]]]
[[Image:Landslide 2.jpg|thumb|Landslide of soil and [[regolith]] in [[Pakistan]] ]]

Deep-seated landslides are those in which the sliding surface is mostly deeply located, for instance well below the maximum rooting depth of trees. They usually involve deep [[regolith]], weathered rock, and/or [[bedrock]] and include large slope failures associated with translational, rotational, or complex movements.<ref>{{Cite journal |last1=Liu |first1=Xin |last2=Wang |first2=Yu |last3=Li |first3=Dian-Qing |date=2020 |title=Numerical simulation of the 1995 rainfall-induced Fei Tsui Road landslide in Hong Kong: new insights from hydro-mechanically coupled material point method |url=https://link.springer.com/10.1007/s10346-020-01442-2 |journal=Landslides |language=en |volume=17 |issue=12 |pages=2755–2775 |doi=10.1007/s10346-020-01442-2 |bibcode=2020Lands..17.2755L |s2cid=219948261 |issn=1612-510X|url-access=subscription }}</ref> They tend to form along a plane of weakness such as a [[Fault (geology)|fault]] or [[bedding plane]]. They can be visually identified by concave [[Fault scarp|scarps]] at the top and steep areas at the toe.<ref>{{cite web |last=Johnson |first=B.F. |date=June 2010 |url=http://www.earthmagazine.org/article/slippery-slopes-how-do-we-insure-against-landslides |title=Slippery slopes |work=Earth magazine |pages=48–55 |access-date=2013-08-28 |archive-date=2014-02-22 |archive-url=https://web.archive.org/web/20140222052004/http://www.earthmagazine.org/article/slippery-slopes-how-do-we-insure-against-landslides |url-status=live }}</ref> Deep-seated landslides also shape [[landscapes]] over geological timescales and produce sediment that strongly alters the course of [[Fluvial landforms of streams|fluvial streams]].<ref>{{cite journal | last1 = Campforts | first1 = B | year = 2022 | title = The Art of Landslides: How Stochastic Mass Wasting Shapes Topography and Influences Landscape Dynamics | journal = Journal of Geophysical Research: Earth Surface | volume = 127 | issue = 8 | pages = 1–23 | article-number = e2022JF006745 | doi=10.1029/2022JF006745 | bibcode = 2022JGRF..12706745C | doi-access = free }}</ref>

==Related phenomena==
* An [[avalanche]], similar in mechanism to a landslide, involves a large amount of ice, snow and rock falling quickly down the side of a mountain.
* A [[pyroclastic flow]] is caused by a collapsing cloud of hot [[volcanic ash|ash]], gas and rocks from a volcanic explosion that moves rapidly down an erupting [[volcano]].
* Extreme precipitation and flow can cause [[Gully|gully formation]] in flatter environments not susceptible to landslides.

=== Resulting tsunamis ===
{{see also|Tsunami#Tsunami generated by landslides}}
Landslides that occur undersea, or have impact into water e.g. significant rockfall or [[volcanic landslide|volcanic collapse]] into the sea,<ref>{{Cite news |title=Ancient Volcano Collapse Caused A Tsunami With An 800-Foot Wave |language=en |work=Popular Science |url=https://www.popsci.com/ancient-volcano-collapse-caused-megatsunami-with-an-800-foot-wave |access-date=2017-10-20 |archive-date=2017-08-29 |archive-url=https://web.archive.org/web/20170829174646/http://www.popsci.com/ancient-volcano-collapse-caused-megatsunami-with-an-800-foot-wave |url-status=live }}</ref> can generate [[tsunami]]s. Massive landslides can also generate [[megatsunami]]s, which are usually hundreds of meters high. In 1958, one such [[1958 Lituya Bay megatsunami|tsunami]] occurred in [[Lituya Bay]] in Alaska.<ref name="Le Bas">{{Citation |last=Le Bas |first=T.P. |title=Submarine mass movements and their consequences: 3rd international symposium |year=2007 |editor-last=Lykousis, Vasilios |chapter=Slope Failures on the Flanks of Southern Cape Verde Islands |publisher=Springer |isbn=978-1-4020-6511-8}}</ref><ref>{{cite journal |last1=Mitchell |first1=N |year=2003 |title=Susceptibility of mid-ocean ridge volcanic islands and seamounts to large scale landsliding |journal=Journal of Geophysical Research |volume=108 |issue=B8 |pages=1–23 |article-number=2002JB001997 |bibcode=2003JGRB..108.2397M |doi=10.1029/2002jb001997 |doi-access=free}}</ref>

==Landslide prediction mapping==
{{see also|Slope stability analysis}}
Landslide hazard analysis and mapping can provide useful information for catastrophic loss reduction, and assist in the development of guidelines for sustainable [[land-use planning]]. The analysis is used to identify the factors that are related to landslides, estimate the relative contribution of factors causing slope failures, establish a relation between the factors and landslides, and to predict the landslide hazard in the future based on such a relationship.<ref>{{cite journal|last1=Chen|first1=Zhaohua|last2=Wang|first2=Jinfei|title=Landslide hazard mapping using logistic regression model in Mackenzie Valley, Canada|journal=Natural Hazards|volume=42|pages=75–89|year=2007|issue=1 |doi=10.1007/s11069-006-9061-6|bibcode=2007NatHa..42...75C |s2cid=128608263}}</ref> The factors that have been used for landslide hazard analysis can usually be grouped into [[geomorphology]], [[geology]], land use/land cover, and [[hydrogeology]]. Since many factors are considered for landslide hazard mapping, [[geographic information system]] (GIS) is an appropriate tool because it has functions of collection, storage, manipulation, display, and analysis of large amounts of spatially referenced data which can be handled fast and effectively.<ref>{{cite journal|last1=Clerici|first1=A|last2=Perego|first2=S|last3=Tellini|first3=C|last4=Vescovi|first4=P|title=A procedure for landslide susceptibility zonation by the conditional analysis method1 |journal=Geomorphology |volume=48 |pages=349–364 |year=2002 |doi=10.1016/S0169-555X(02)00079-X |issue=4|bibcode = 2002Geomo..48..349C }}</ref> Cardenas reported evidence on the exhaustive use of GIS in conjunction of uncertainty modelling tools for landslide mapping.<ref>{{cite journal |last=Cardenas |first=IC|title=Landslide susceptibility assessment using Fuzzy Sets, Possibility Theory and Theory of Evidence. Estimación de la susceptibilidad ante deslizamientos: aplicación de conjuntos difusos y las teorías de la posibilidad y de la evidencia. |journal=Ingenieria e Investigación |year=2008 |volume=28 |issue=1 |url=https://www.researchgate.net/publication/232301120}}</ref><ref>{{cite journal|last=Cardenas|first=IC|title=Non-parametric modeling of rainfall in Manizales City (Colombia) using multinomial probability and imprecise probabilities. Modelación no paramétrica de lluvias para la ciudad de Manizales, Colombia: una aplicación de modelos multinomiales de probabilidad y de probabilidades imprecisas|journal=Ingenieria e Investigación |year=2008|volume=28|issue=2|url=https://www.researchgate.net/publication/232301359}}</ref> [[Remote sensing]] techniques are also highly employed for landslide hazard assessment and analysis. Before and after aerial photographs and satellite imagery are used to gather landslide characteristics, like distribution and classification, and factors like slope, [[lithology]], and land use/land cover to be used to help predict future events.<ref>{{cite journal|last1=Metternicht|first1=G|author-link=Graciela Metternicht|last2=Hurni|first2=L|last3=Gogu|first3=R|year=2005|title=Remote sensing of landslides: An analysis of the potential contribution to geo-spatial systems for hazard assessment in mountainous environments|journal=Remote Sensing of Environment|volume=98|issue=2–3|pages=284–303|bibcode=2005RSEnv..98..284M|doi=10.1016/j.rse.2005.08.004}}</ref> Before and after imagery also helps to reveal how the landscape changed after an event, what may have triggered the landslide, and shows the process of regeneration and recovery.<ref>{{cite journal |last1=De La Ville|first1=Noemi|last2=Chumaceiro Diaz|first2=Alejandro|last3=Ramirez|first3=Denisse|url=http://www.vliz.be/imisdocs/publications/35254.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.vliz.be/imisdocs/publications/35254.pdf |archive-date=2022-10-09 |url-status=live|title=Remote Sensing and GIS Technologies as Tools to Support Sustainable Management of Areas Devastated by Landslides|journal=Environment, Development and Sustainability|volume=4|pages=221–229|year=2002|doi=10.1023/A:1020835932757|issue=2|bibcode=2002EDSus...4..221D |s2cid=152358230}}</ref>

Using satellite imagery in combination with GIS and on-the-ground studies, it is possible to generate maps of likely occurrences of future landslides.<ref>{{Cite book |title=Advances in remote sensing for infrastructure monitoring |date=2021 |publisher=Springer |isbn=978-3-030-59109-0 |editor-last=Singhroy |editor-first=Vernon |series=Springer remote sensing/photogrammetry |location=Cham}}</ref><ref>{{cite journal|last1=Fabbri|first1=Andrea G.|last2=Chung|first2=Chang-Jo F.|last3=Cendrero|first3=Antonio|last4=Remondo|first4=Juan|title=Is Prediction of Future Landslides Possible with a GIS?|journal=Natural Hazards|volume=30|pages=487–503|year=2003|doi=10.1023/B:NHAZ.0000007282.62071.75|issue=3|bibcode=2003NatHa..30..487F |s2cid=129661820}}</ref> Such maps should show the locations of previous events as well as clearly indicate the probable locations of future events. In general, to predict landslides, one must assume that their occurrence is determined by certain geologic factors, and that future landslides will occur under the same conditions as past events.<ref>{{cite journal|last1=Lee|first1=S|last2=Talib|first2=Jasmi Abdul|title=Probabilistic landslide susceptibility and factor effect analysis|journal=Environmental Geology|volume=47|pages=982–990|year=2005|doi=10.1007/s00254-005-1228-z|issue=7|s2cid=128534998}}</ref> Therefore, it is necessary to establish a relationship between the geomorphologic conditions in which the past events took place and the expected future conditions.<ref>{{cite journal|last1=Ohlmacher|first1=G|title=Using multiple logistic regression and GIS technology to predict landslide hazard in northeast Kansas, USA|journal=Engineering Geology|volume=69|pages=331–343|year=2003|doi=10.1016/S0013-7952(03)00069-3|issue=3–4|bibcode=2003EngGe..69..331O}}</ref>

[[Natural disasters]] are a dramatic example of people living in conflict with the environment. Early predictions and warnings are essential for the reduction of property damage and loss of life. Because landslides occur frequently and can represent some of the most destructive forces on earth, it is imperative to have a good understanding as to what causes them and how people can either help prevent them from occurring or simply avoid them when they do occur. [[Sustainable land management]] and development is also an essential key to reducing the negative impacts felt by landslides.

[[File:SlideMinder Extensometer.png|thumb|A Wireline [[extensometer]] monitoring slope displacement and transmitting data remotely via radio or Wi-Fi. In situ or strategically deployed extensometers may be used to provide early warning of a potential landslide.<ref>{{cite journal |last1=Rose |first1=Nick D. |last2=Hunger |first2=Oldrich |url=http://www.engr.usask.ca/classes/GEOE/315/notes/SlopeFailure_Velocity.pdf |title=Forecasting potential slope failure in open pit mines |archive-url=https://web.archive.org/web/20170713063040/http://www.engr.usask.ca/classes/GEOE/315/notes/SlopeFailure_Velocity.pdf |archive-date=2017-07-13 |journal=Journal of Rock Mechanics & Mining Sciences |date=17 February 2006 |access-date=20 August 2015}}</ref>]]

GIS offers a superior method for landslide analysis because it allows one to capture, store, manipulate, analyze, and display large amounts of data quickly and effectively. Because so many variables are involved, it is important to be able to overlay the many layers of data to develop a full and accurate portrayal of what is taking place on the Earth's surface. Researchers need to know which variables are the most important factors that trigger landslides in any given location. Using GIS, extremely detailed maps can be generated to show past events and likely future events which have the potential to save lives, property, and money.

Since the '90s, GIS have been also successfully used in conjunction to [[decision support system]]s, to show on a map real-time risk evaluations based on monitoring data gathered in the area of the [[Val Pola landslide|Val Pola disaster]] (Italy).<ref>{{Cite journal|last1=Lazzari|first1=M.|last2=Salvaneschi|first2=P.|year=1999|title=Embedding a Geographic Information System in a Decision Support System for Landslide Hazard Monitoring|url=https://dinamico2.unibg.it/lazzari/doc/embedding-authors-copy.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://dinamico2.unibg.it/lazzari/doc/embedding-authors-copy.pdf |archive-date=2022-10-09 |url-status=live|journal=Natural Hazards|volume=20|issue=2–3|pages=185–195|doi=10.1023/A:1008187024768|bibcode=1999NatHa..20..185L |s2cid=1746570}}</ref>

<gallery widths="200px" heights="155px" class="center">
Image:Global Landslide Risks.jpg|Global landslide risks
File:2024 United States landslide map.jpg|2024 United States landslide risk map
File:Ferguson-slide.jpg|[[Ferguson landslide|Ferguson Slide]] on [[California State Route 140]] in June 2006
File:Rock_slide_detector_UPRR_Sierra_grade_at_"Cape_Horn",_Colfax,_CA.jpg|Trackside rock slide detector on the [[Union Pacific Railroad|UPRR]] Sierra grade near [[Colfax, California|Colfax, CA]]
</gallery>

== Prehistoric landslides ==
[[Image:Rhine cutting through Flims Rockslide debris.jpg|thumb|[[Rhine]] cutting through [[Flims Rockslide]] debris, Switzerland]]

* [[Storegga Slide]], some 8,000 years ago off the western coast of [[Norway]]. Caused massive [[tsunamis]] in [[Doggerland]] and other areas connected to the [[North Sea]]. A total volume of {{convert|3,500|km3|abbr=on}} debris was involved; comparable to a {{convert|34|m|ft|abbr=on}} thick area the size of Iceland. The submarine landslide is thought to be among the largest in history.<ref>{{Cite journal |last1=Bugge |first1=Tom |last2=Befring |first2=Stein |last3=Belderson |first3=Robert H. |last4=Eidvin |first4=Tor |last5=Jansen |first5=Eystein |last6=Kenyon |first6=Neil H. |last7=Holtedahl |first7=Hans |last8=Sejrup |first8=Hans Petter |date=December 1987 |title=A giant three-stage submarine slide off Norway |url=http://link.springer.com/10.1007/BF02242771 |journal=Geo-Marine Letters |language=en |volume=7 |issue=4 |pages=191–198 |doi=10.1007/BF02242771 |bibcode=1987GML.....7..191B |issn=0276-0460|url-access=subscription }}</ref>
* Landslide which moved [[Heart Mountain (Wyoming)|Heart Mountain]] to its current location, the largest continental landslide discovered so far. In the 48&nbsp;million years since the slide occurred, erosion has removed most of the portion of the slide.
* [[Flims Rockslide]], about {{convert|12|km3|mi3|abbr=on}}, Switzerland, some 10,000 years ago in post-glacial [[Pleistocene]]/[[Holocene]], the largest so far described in the Alps and on dry land that can be easily identified in a modestly eroded state.<ref>[http://www.angewandte-geologie.ch/Archiv/Volumes/vol112.htm Weitere Erkenntnisse und weitere Fragen zum Flimser Bergsturz] {{webarchive|url=https://web.archive.org/web/20110706221400/http://www.angewandte-geologie.ch/Archiv/Volumes/vol112.htm |date=2011-07-06 }} A.v. Poschinger, Angewandte Geologie, Vol. 11/2, 2006</ref>
* The landslide around 200&nbsp;BC which formed [[Lake Waikaremoana]] on the [[North Island]] of New Zealand, where a large block of the Ngamoko Range slid and dammed a gorge of Waikaretaheke River, forming a natural reservoir up to {{convert|256|m}} deep.
* [[Cheekye Fan]], [[British Columbia]], Canada, about {{convert|25|km2|mi2|abbr=on}}, [[Late Pleistocene]] in age.
* The Manang-Braga rock avalanche/debris flow may have formed Marsyangdi Valley in the Annapurna Region, [[Nepal]], during an interstadial period belonging to the last glacial period.<ref>{{Cite journal|title=Two large late quaternary rock slope failures and their geomorphic significance, Annapurna, Himalayas (Nepal)|journal=Geografia Fisica e Dinamica Quaternaria|volume=34 |year=2011|pages=5–16|author=Fort, Monique|url=https://www.researchgate.net/publication/235964481}}</ref> Over {{cvt|15|km3}} of material are estimated to have been moved in the single event, making it one of the largest continental landslides.{{Citation needed|date=October 2022}}
* [[Tsergo Ri landslide]], a massive slope failure {{cvt|60|km}} north of Kathmandu, Nepal, involving an estimated {{cvt|10|to|15|km3}}.<ref>{{Cite journal|last1=Weidinger|first1=Johannes T.|last2=Schramm|first2=Josef-Michael|last3=Nuschej|first3=Friedrich|date=2002-12-30|title=Ore mineralization causing slope failure in a high-altitude mountain crest—on the collapse of an 8000 m peak in Nepal|journal=Journal of Asian Earth Sciences|volume=21|issue=3|pages=295–306|doi=10.1016/S1367-9120(02)00080-9|bibcode=2002JAESc..21..295W}}</ref> Prior to this landslide the mountain may have been the world's 15th mountain above {{cvt|8000|m|ft|0}}.

==Historical landslides==
{{main|List of landslides}}
* The [[1806 Goldau landslide]] on 2 September 1806
* The Cap Diamant [[Québec rockslide]] on 19 September 1889
* [[Frank Slide]], Turtle Mountain, [[Alberta]], Canada, on 29 April 1903
* [[Khait landslide]], Khait, [[Tajik Soviet Socialist Republic|Tajikistan]], Soviet Union, on 10 July 1949
* A [[1959 Hebgen Lake earthquake|magnitude 7.5 earthquake]] in Yellowstone Park (17 August 1959) caused a landslide that blocked the Madison River, and created Quake Lake.
* [[Monte Toc]] landslide ({{convert|260|e6m3|abbr=off|disp=semicolon}}) falling into the [[Vajont Dam]] basin in Italy, causing a [[megatsunami]] and about 2000 deaths, on 9 October 1963
* [[Hope Slide]] landslide ({{convert|46|e6m3|abbr=off|disp=semicolon}}) near [[Hope, British Columbia]] on 9 January 1965.<ref>{{Cite bcgnis|id=53154 |title=Hope Slide}}</ref>
* The 1966 [[Aberfan disaster]]
* [[Tuve landslide]] in [[Gothenburg]], Sweden on 30 November 1977.
* The [[1979 Abbotsford landslip]], [[Dunedin]], New Zealand on 8 August 1979.
* The [[1980 eruption of Mount St. Helens|eruption of Mount St. Helens]] (18 May 1980) caused an enormous landslide when the top 1300 feet of the volcano suddenly gave way.
* [[Val Pola landslide]] during [[Valtellina disaster]] (1987) Italy
* [[1997 Thredbo landslide|Thredbo landslide]], Australia on 30 July 1997, destroyed hostel.
* [[1999 Vargas mudslides|Vargas mudslides]], due to heavy rains in [[Vargas State]], Venezuela, in December, 1999, causing tens of thousands of deaths.
* [[2005 La Conchita landslide]] in Ventura, [[California]] causing 10 deaths.
* [[2006 Southern Leyte mudslide]] in [[Saint Bernard, Southern Leyte]], causing 1,126 deaths and buried the village of Guinsaugon.
* [[2007 Chittagong mudslide]], in [[Chittagong]], Bangladesh, on 11 June 2007.
* [[2008 Cairo landslide]] on 6 September 2008.
* [[:it:Alluvione di Messina del 2009|The 2009 Peloritani Mountains]] disaster caused 37 deaths, on October 1.<ref>{{Cite journal|last1=Peres|first1=D. J.|last2=Cancelliere|first2=A.|date=2016-10-01|title=Estimating return period of landslide triggering by Monte Carlo simulation|journal=Journal of Hydrology|series=Flash floods, hydro-geomorphic response and risk management|volume=541|pages=256–271|doi=10.1016/j.jhydrol.2016.03.036|bibcode=2016JHyd..541..256P}}</ref>
* The [[2010 Uganda landslide]] caused over 100 deaths following heavy rain in [[Bududa District|Bududa]] region.
* [[2010 Gansu mudslide|Zhouqu county mudslide]] in [[Gansu]], China on 8 August 2010.<ref>{{cite web |url=http://www.easyseosolution.com/blog/archives/932 |title=Large landslide in Gansu Zhouqu August 7 |publisher=Easyseosolution.com |date=19 August 2010 |archive-url=https://web.archive.org/web/20100824060054/http://www.easyseosolution.com/blog/archives/932 |archive-date=24 August 2010 }}</ref>
* [[Devil's Slide (California)|Devil's Slide]], an ongoing landslide in [[San Mateo County, California]]
* [[January 2011 Rio de Janeiro floods and mudslides|2011 Rio de Janeiro landslide]] in [[Rio de Janeiro State|Rio de Janeiro]], Brazil on 11 January 2011, causing 610 deaths.<ref>{{cite news |url=https://www.cbc.ca/news/world/brazil-mudslide-death-toll-passes-450-1.1035927 |title=Brazil mudslide death toll passes 450 |publisher=Canadian Broadcasting Corporation |date=13 January 2011 |access-date=13 January 2011 |archive-date=1 March 2011 |archive-url=https://web.archive.org/web/20110301033218/http://www.cbc.ca/news/world/story/2011/01/13/brazil-flood-deaths.html |url-status=live }}</ref>
* [[2014 Pune landslide]], in [[Pune]], India.
* [[2014 Oso mudslide]], in [[Oso, Washington]]
* [[2017 Mocoa landslide]], in [[Mocoa]], Colombia
* [[2022 Ischia landslide]]
* [[2024 Gofa landslides]], in [[Gofa Zuria|Gofa]], Ethiopia
* [[2024 Wayanad landslides]], in [[Wayanad district|Wayanad]], [[Kerala]], India
* 2025, in [[Blatten (Lötschen)]], Switzerland
* [[2025 Tarasin landslide]], [[Sudan]]

==Extraterrestrial landslides==
Evidence of past landslides has been detected on many bodies in the [[Solar System]], but since most observations are made by probes that only observe for a limited time and most bodies in the Solar System appear to be geologically inactive not many landslides are known to have happened in recent times. Both Venus and Mars have been subject to long-term mapping by orbiting satellites, and examples of landslides have been observed on both planets.

<gallery widths="200px" heights="160px" class="center">
Image:Venus-Landslide.jpg|Before and after radar images of a landslide on Venus. In the center of the image on the right, the new landslide, a bright, flow-like area, can be seen extending to the left of a bright fracture. 1990 image.
Image:Avalanche on Mars February 19th 2008 01.jpg|Landslide in progress on Mars, 2008-02-19
</gallery>

== Landslide mitigation ==
{{excerpt|Landslide mitigation}}

==Landslide monitoring==
The monitoring of landslides is essential for estimating the dangerous situations, making it possible to issue alerts on time, to avoid loses of lives and property, and to have proper planning and reducing measures in place. Currently, there exist different type of techniques aimed to monitor landslides:

=== [[Remote sensing]] techniques ===

* [[Interferometric synthetic-aperture radar|InSAR]] (Interferometric Synthetic Aperture Radar): This remote sensing technique measures ground displacement over time with high precision. It is ideal for large-scale monitoring.<ref>{{Cite journal |last1=Tomás |first1=Roberto |last2=Zeng |first2=Qiming |last3=Lopez-Sanchez |first3=Juan M. |last4=Zhao |first4=Chaoying |last5=Li |first5=Zhenhong |last6=Liu |first6=Xiaojie |last7=Navarro-Hernández |first7=María I. |last8=Hu |first8=Liuru |last9=Luo |first9=Jiayin |last10=Díaz |first10=Esteban |last11=Szeibert |first11=William T. |last12=Pastor |first12=José Luis |last13=Riquelme |first13=Adrián |last14=Yu |first14=Chen |last15=Cano |first15=Miguel |title=Advances on the investigation of landslides by space-borne synthetic aperture radar interferometry |journal=Geo-Spatial Information Science |date=2024-05-03 |volume=27 |issue=3 |pages=602–623 |url=https://www.tandfonline.com/doi/full/10.1080/10095020.2023.2266224 |doi=10.1080/10095020.2023.2266224 |bibcode=2024GSIS...27..602T |issn=1009-5020|hdl=10045/138430 |hdl-access=free }}</ref><ref name=":7">{{Cite journal |last1=Casagli |first1=N. |last2=Cigna |first2=F. |last3=Bianchini |first3=S. |last4=Hölbling |first4=D. |last5=Füreder |first5=P. |last6=Righini |first6=G. |last7=Del Conte |first7=S. |last8=Friedl |first8=B. |last9=Schneiderbauer |first9=S. |last10=Iasio |first10=C. |last11=Vlcko |first11=J. |last12=Greif |first12=V. |last13=Proske |first13=H. |last14=Granica |first14=K. |last15=Falco |first15=S. |date=2016-10-01 |title=Landslide mapping and monitoring by using radar and optical remote sensing: Examples from the EC-FP7 project SAFER |url=https://linkinghub.elsevier.com/retrieve/pii/S2352938516300635 |journal=Remote Sensing Applications: Society and Environment |volume=4 |pages=92–108 |doi=10.1016/j.rsase.2016.07.001 |bibcode=2016RSASE...4...92C |issn=2352-9385|hdl=2158/1045254 |hdl-access=free }}</ref>
* [[Lidar|LiDAR]] (Light Detection and Ranging): Provides detailed 3D models of terrain to detect changes over time by comparison of different point clouds acquired over time.<ref>{{Cite journal |last1=Tomás |first1=R. |last2=Abellán |first2=A. |last3=Cano |first3=M. |last4=Riquelme |first4=A. |last5=Tenza-Abril |first5=A. J. |last6=Baeza-Brotons |first6=F. |last7=Saval |first7=J. M. |last8=Jaboyedoff |first8=M. |date=2018-02-01 |title=A multidisciplinary approach for the investigation of a rock spreading on an urban slope |journal=Landslides |language=en |volume=15 |issue=2 |pages=199–217 |doi=10.1007/s10346-017-0865-0 |bibcode=2018Lands..15..199T |issn=1612-5118|doi-access=free |hdl=10045/73318 |hdl-access=free }}</ref><ref>{{Cite journal |last1=Jaboyedoff |first1=Michel |last2=Oppikofer |first2=Thierry |last3=Abellán |first3=Antonio |last4=Derron |first4=Marc-Henri |last5=Loye |first5=Alex |last6=Metzger |first6=Richard |last7=Pedrazzini |first7=Andrea |date=March 2012 |title=Use of LIDAR in landslide investigations: a review |journal=Natural Hazards |language=en |volume=61 |issue=1 |pages=5–28 |doi=10.1007/s11069-010-9634-2 |bibcode=2012NatHa..61....5J |issn=0921-030X|doi-access=free }}</ref>
* Optical satellite imagery: Useful for identifying surface changes, geomorphological features (e.g. cracks and scarps) and mapping landslide-prone areas.<ref name=":7" />
* [[Unmanned aerial vehicle|UAVs]] (Unmanned Aerial Vehicles): This technique captures high-resolution images and topographic data in inaccessible areas.<ref>{{Cite journal |last1=Sun |first1=Jianwei |last2=Yuan |first2=Guoqin |last3=Song |first3=Laiyun |last4=Zhang |first4=Hongwen |date=January 2024 |title=Unmanned Aerial Vehicles (UAVs) in Landslide Investigation and Monitoring: A Review |journal=Drones |language=en |volume=8 |issue=1 |page=30 |doi=10.3390/drones8010030 |doi-access=free |bibcode=2024Drone...8...30S |issn=2504-446X}}</ref>
* Thermal imaging: Thermal images enable to detects temperature variations that may indicate water movement or stress in the slope.<ref>{{Cite journal |last1=Cosentino |first1=Antonio |last2=Marmoni |first2=Gian Marco |last3=Fiorucci |first3=Matteo |last4=Mazzanti |first4=Paolo |last5=Scarascia Mugnozza |first5=Gabriele |last6=Esposito |first6=Carlo |date=January 2023 |title=Optical and Thermal Image Processing for Monitoring Rainfall Triggered Shallow Landslides: Insights from Analogue Laboratory Experiments |journal=Remote Sensing |language=en |volume=15 |issue=23 |page=5577 |doi=10.3390/rs15235577 |doi-access=free |bibcode=2023RemS...15.5577C |issn=2072-4292|hdl=11573/1707707 |hdl-access=free }}</ref>

=== Ground-based techniques ===

* [[Global Positioning System|GPS]] (Global Positioning System): Tracks ground movements at specific points over time using a constellation of satellites orbiting around the Earth.
* [[Topographic survey]]s: Measures displacements of marked targets on a slope.
* [[Ground-Based Radar Prototype|Ground-based radar]] (GB-SAR): Continuously monitors surface deformation using a SAR sensor and detects movement in real-time. It follows the same principle than InSAR.<ref>{{Cite journal |last1=Noferini |first1=Linhsia |last2=Pieraccini |first2=Massimiliano |last3=Mecatti |first3=Daniele |last4=Macaluso |first4=Giovanni |last5=Atzeni |first5=Carlo |last6=Mantovani |first6=Matteo |last7=Marcato |first7=Gianluca |last8=Pasuto |first8=Alessandro |last9=Silvano |first9=Sandro |last10=Tagliavini |first10=Fabrizio |date=2007-12-07 |title=Using GB-SAR technique to monitor slow moving landslide |url=https://linkinghub.elsevier.com/retrieve/pii/S0013795207001822 |journal=Engineering Geology |volume=95 |issue=3 |pages=88–98 |doi=10.1016/j.enggeo.2007.09.002 |bibcode=2007EngGe..95...88N |issn=0013-7952|url-access=subscription }}</ref>

=== Geotechnical instrumentation ===

* [[Piezometers]]: Monitors groundwater levels and pore water pressure, which are critical triggers for landslides.
* [[Load cell]]s: Measures stress changes in retaining structures or anchors.
* [[Tiltmeter]]s: Detects small angular changes in the slope surface or retaining walls. 
* [[Extensometer]]s: Measures displacement along cracks or tension zones.
* [[Inclinometer]]s: Detects subsurface movements by monitoring changes in the inclination of a borehole.<ref>{{Cite journal |last1=Bordoni |first1=Massimiliano |last2=Vivaldi |first2=Valerio |last3=Bonì |first3=Roberta |last4=Spanò |first4=Simone |last5=Tararbra |first5=Mauro |last6=Lanteri |first6=Luca |last7=Parnigoni |first7=Matteo |last8=Grossi |first8=Alessandra |last9=Figini |first9=Silvia |last10=Meisina |first10=Claudia |date=2023-01-01 |title=A methodology for the analysis of continuous time-series of automatic inclinometers for slow-moving landslides monitoring in Piemonte region, northern Italy |journal=Natural Hazards |language=en |volume=115 |issue=2 |pages=1115–1142 |doi=10.1007/s11069-022-05586-3 |bibcode=2023NatHa.115.1115B |issn=1573-0840|doi-access=free }}</ref>

=== Seismic techniques ===
•Geophones and accelerometers: Detect seismic vibrations or movements that might indicate slope instability.

== Climate-change impact on landslides ==
Climate-change impact on temperature, both average rainfall and rainfall extremes, and evapotranspiration may affect landslide distribution, frequency and intensity.<ref>62. Gariano, S.L.; Guzzetti F. (2016). "Landslides in a Changing Climate". ''Earth-Science Reviews'', 162, 227–252. {{doi|10.1016/j.earscirev.2016.08.011}}</ref> However, this impact shows strong variability in different areas.<ref name=":8">63. Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge and New York, pp. 1767–1926. {{doi|10.1017/9781009157896.014}}.</ref> Therefore, the effects of climate change on landslides need to be studied on a regional scale.  Climate change can have both positive and negative impacts on landslides. Temperature rise may increase evapotranspiration, leading to a reduction in soil moisture and stimulate vegetation growth, also due to a CO<sub>2</sub> increase in the atmosphere. Both effects may reduce landslides in some conditions. On the other side, temperature rise causes an increase of landslides due to
* the acceleration of snowmelt and an increase of rain on snow during spring, leading to strong infiltration events.<ref>64. Cardinali, M., Ardizzone, F., Galli, M., Guzzetti, F., & Reichenbach, P. (2000, January). "[https://geomorphology.irpi.cnr.it/publications/repository/public/proceedings/2000/landslides-triggered-by-rapid-snow-melting-the-december-1996-january-1997-event-in-central-italy.pdf Landslides triggered by rapid snow melting: the December 1996–January 1997 event in Central Italy]". In ''Proceedings 1st Plinius Conference on Mediterranean Storms'' (pp. 439–448).</ref>
* Permafrost degradation that reduces the cohesion of soils and rock masses due to the loss of interstitial ice.<ref>65.Krautblatter, M., Funk, D., & Günzel, F. K. (2013). "Why permafrost rocks become unstable: a rock–ice‐mechanical model in time and space". ''Earth Surface Processes and Landforms'', 38(8), 876–887.  {{doi|10.1002/esp.3374}}</ref> This mainly occurs at high elevation.  
* Glacier retreat that has the dual effect of relieving mountain slopes and increasing their steepness.

Since the average precipitation is expected to decrease or increase regionally,<ref name=":8" /> rainfall induced landslides may change accordingly, due to changes in infiltration, groundwater levels and river bank erosion. Weather extremes are expected to increase due to climate change including heavy precipitation.<ref name=":8" /> This yields negative effects on landslides due to focused infiltration in soil and rock<ref>66. Ciabatta, L., Camici, S., Brocca, L., Ponziani, F., Stelluti, M., Berni, N., & Moramarco, T.J.J.O.H. (2016). "Assessing the impact of climate-change scenarios on landslide occurrence in Umbria Region, Italy". ''Journal of Hydrology'', 541, 285–295. {{doi|10.1016/j.jhydrol.2016.02.007}}</ref> and an increase of runoff events, which may trigger debris flows.

== See also ==
{{colbegin}}
* [[Avalanche]]
* [[California landslides]]
* [[Deformation monitoring]]
* [[Earthquake engineering]]
* [[Geotechnical engineering]]
* [[Huayco]]
* [[Landslide dam]]
* [[Natural disaster]]
* [[Railway slide fence]]
* [[Rockslide]]
* [[Sector collapse]]
* [[Slump (geology)]]
* [[Urban search and rescue]]
* [[Washaway]]
{{colend}}

==References==
{{reflist}}
==External links==
{{Commons category|Landslides}}
* [https://web.archive.org/web/20020325150633/http://landslides.usgs.gov/ United States Geological Survey site] (archived 25 March 2002)
* [http://www.bgs.ac.uk/landslides/ British Geological Survey landslides site]
* [http://www.bgs.ac.uk/landslides/NLD.html British Geological Survey National Landslide Database]
* [http://icl.iplhq.org/ International Consortium on Landslides]{{Dead link|date=February 2025 |bot=InternetArchiveBot |fix-attempted=yes }}

{{Geotechnical engineering|state=collapsed}}
{{Natural disasters}}
{{sediment transport}}

{{Authority control}}

[[Category:Landslides| ]]
[[Category:Environmental soil science]]
[[Category:Hazards of outdoor recreation]]
[[Category:Natural disasters]]

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