Editing Landslide (section)

====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|pages=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|pages=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|pages=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|pages=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}}</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|pages=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.]]