Mass wasting, also known as mass movement, is a general term for the movement of

rock Rock most often refers to: * Rock (geology), a naturally occurring solid aggregate of minerals or mineraloids * Rock music, a genre of popular music Rock or Rocks may also refer to: Places United Kingdom * Rock, Caerphilly, a location in Wales ...

soil Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...

down slopes under the force of

gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...

. It differs from other processes of

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

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 Solifluction is a collective name for gradual processes in which a mass moves down a slope ("mass wasting") related to freeze-thaw activity. This is the standard modern meaning of solifluction, which differs from the original meaning given to it ...

rockfall A rockfall or rock-fallWhittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984. . is a quantity/sheets of rock that has fallen freely from a cliff face. The term is also used for collapse of rock from roof or walls of min ...

debris flow Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally ...

s, and

landslide Landslides, also known as landslips, are several forms of mass wasting that may include a wide range of ground movements, such as rockfalls, deep-seated grade (slope), slope failures, mudflows, and debris flows. Landslides occur in a variety of ...

s, 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 Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury (planet), Mercury. In the English language, Mars is named for the Mars (mythology), Roman god of war. Mars is a terr ...

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never fa ...

, Jupiter's moons Io, and on many other bodies in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar S ...

Subsidence Subsidence is a general term for downward vertical movement of the Earth's surface, which can be caused by both natural processes and human activities. Subsidence involves little or no horizontal movement, which distinguishes it from slope move ...

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 Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including public works such as roads, bridges, canals, dams, airports, sewage ...

, as creep can deform roadways and structures and break pipelines. Mitigation methods include

slope stabilization Slope stability analysis is a static or dynamic, analytical or empirical method to evaluate the stability of earth and rock-fill dams, embankments, excavated slopes, and natural slopes in soil and rock. Slope stability refers to the condition of i ...

, construction of walls, catchment dams, or other structures to contain rockfall or debris flows,

afforestation Afforestation is the establishment of a forest or stand of trees (forestation) in an area where there was no previous tree cover. Many government and non-governmental organizations directly engage in afforestation programs to create forests a ...

, or improved drainage of source areas.

Types

Mass wasting is a general term for any process of

that is driven by

and in which the transported soil and rock is not entrained in a moving medium, such as water, wind, or ice. 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 A mudflow or mud flow is a form of mass wasting involving fast-moving flow of debris that has become liquified by the addition of water. Such flows can move at speeds ranging from 3 meters/minute to 5 meters/second. Mudflows contain a significa ...

(mass wasting) and a very muddy

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...

(stream erosion), without a sharp dividing line. Many forms of mass wasting are recognized, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years. Based on how the soil, regolith or rock moves downslope as a whole, mass movements can be broadly classified as either creeps or

is sometimes also 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.

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

terracette A terracette is a landform consisting of a hillside ridge arranged as part of sub-parallel "step-like sequences" of such ridges. Terracette occur on step hillsides and are regularly spaced. Various causes have been suggested to explain their origi ...

s. 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.

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 Permafrost is ground that continuously remains below 0 °C (32 °F) for two or more years, located on land or under the ocean. Most common in the Northern Hemisphere, around 15% of the Northern Hemisphere or 11% of the global surface ...

and receive a constant supply of new debris by

weathering Weathering is the deterioration of rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little or no movement), ...

. Solifluction affects the entire slope rather than being confined to channels and can produce terrace-like landforms or

stone rivers A stone run (called also ''stone river'', ''stone stream'' or ''stone sea'' 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 avalanche Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generally ...

s, then earthflows, then

s. Further increase in water content produces a sheetflood, which is a form of

sheet erosion Sheet erosion or sheet wash is the even erosion of substrate along a wide area. It occurs in a wide range of settings such as coastal plains, hillslopes, floodplains, beaches, savanna plains and semi-arid plains. Water moving fairly uniformly with ...

rather than mass wasting.

Occurrences

, mass wasting occurs on both terrestrial and submarine slopes. 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. Mass wasting is a common phenomenon throughout the Solar System, occurring where volatile materials are lost from a

regolith Regolith () is a blanket of unconsolidated, loose, heterogeneous superficial deposits covering solid rock. It includes dust, broken rocks, and other related materials and is present on Earth, the Moon, Mars, some asteroids, and other terrestria ...

. Such mass wasting has been observed on

, Io,

Triton Triton commonly refers to: * Triton (mythology), a Greek god * Triton (moon), a satellite of Neptune Triton may also refer to: Biology * Triton cockatoo, a parrot * Triton (gastropod), a group of sea snails * ''Triton'', a synonym of ''Triturus' ...

, and possibly

Europa Europa may refer to: Places * Europe * Europa (Roman province), a province within the Diocese of Thrace * Europa (Seville Metro), Seville, Spain; a station on the Seville Metro * Europa City, Paris, France; a planned development * Europa Cliff ...

and Ganymede. Mass wasting also occurs in the equatorial regions of

, where stopes of soft

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...

-rich sediments are steepened by wind erosion. Mass wasting on

is associated with the rugged terrain of

tessera A tessera (plural: tesserae, diminutive ''tessella'') is an individual tile, usually formed in the shape of a square, used in creating a mosaic. It is also known as an abaciscus or abaculus. Historical tesserae The oldest known tesserae ...

e. Io shows extensive mass wasting of its volcanic mountains.

Deposits and landforms

Mass wasting affects

geomorphology Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n ...

, 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 Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...

(rock fragments) are oriented perpendicular to the contours of the deposit. Rockfall can produce

talus slope Scree is a collection of broken rock fragments at the base of a cliff or other steep rocky mass that has accumulated through periodic rockfall. Landforms associated with these materials are often called talus deposits. Talus deposits typically h ...

s at the feet of cliffs. A more dramatic manifestation of rockfall is

rock glacier Rock glaciers are distinctive geomorphological landforms, consisting either of angular rock debris frozen in interstitial ice, former "true" glaciers overlain by a layer of talus, or something in-between. Rock glaciers are normally found at high ...

s, 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 Boudinaged quartz vein in shear foliation, Starlight Pit, Fortnum Gold Mine, Western Australia. Boudinage is a geological term for structures formed by extension, where a rigid tabular body such as hornfels, is stretched and deformed amids ...

) and zones of concentrated shear. Debris flow deposits take the form of long, narrow tracks of very poorly sorted material. These may have natural

levee A levee (), dike (American English), dyke (English in the Commonwealth of Nations, Commonwealth English), embankment, floodbank, or stop bank is a structure that is usually soil, earthen and that often runs parallel (geometry), parallel to ...

s at the sides of the tracks, and sometimes consist of lenses of rock fragments alternating with lenses of fine-grained earthy material. Debris flows often form much of the upper slopes of

alluvial fan An alluvial fan is an accumulation of sediments that fans outwards from a concentrated source of sediments, such as a narrow canyon emerging from an escarpment. They are characteristic of mountainous terrain in arid to semiarid climates, but a ...

Causes

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

lithology The lithology of a rock unit is a description of its physical characteristics visible at outcrop, in hand or core samples, or with low magnification microscopy. Physical characteristics include colour, texture, grain size, and composition. Lit ...

. Unconsolidated or weak debris are more susceptible to mass wasting, as are materials that lose cohesion when wetted. *

Stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

, such as thinly bedded rock or alternating beds of weak and strong or impermeable or permiable rock lithologies. * Faults or other geologic structures that weaken the rock. *

Topography Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary sci ...

, such as steep slopes or cliffs. *

Climate Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...

, with large temperature swings, frequent freezing and thawing, or abundant rainfall * Lack of vegetation Activating causes include: * Undercutting of the slope by excavation or erosion * Increased overburden from structures * Increased soil moisture *

Earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

Hazards and mitigation

Mass wasting causes problems for

, particularly highway construction. It can displace roads, buildings, and other construction and can break pipelines. Historically, mitigation of landslide hazards on the

Gaillard Cut The Culebra Cut, formerly called Gaillard Cut, is an artificial valley that cuts through the Continental Divide in Panama. The cut forms part of the Panama Canal, linking Gatun Lake, and thereby the Atlantic Ocean, to the Gulf of Panama and hence ...

of the

Panama Canal The Panama Canal ( es, Canal de Panamá, link=no) is an artificial waterway in Panama that connects the Atlantic Ocean with the Pacific Ocean and divides North and South America. The canal cuts across the Isthmus of Panama and is a conduit ...

accounted for of the of material removed while excavating the cut.

Rockslide A rockslide is a type of landslide caused by rock failure in which part of the bedding plane of failure passes through compacted rock and material collapses ''en masse'' and not in individual blocks. Note that a rockslide is similar to an avalanc ...

s or

s can have disastrous consequences, both immediate and delayed. The

Oso disaster A major landslide occurred east of Oso, Washington, United States, on March 22, 2014, at 10:37 a.m. local time. A portion of an unstable hill collapsed, sending mud and debris to the south across the North Fork of the Stillaguamish River, ...

of March 2014 was a landslide that caused 43 fatalities in

Oso, Washington Oso is a census-designated place (CDP) in Snohomish County, Washington, United States. It is located to the west of Darrington, south of the North Fork of the Stillaguamish River and approximately 50 air miles (80 km) from Seattle. The popu ...

, US. Delayed consequences of landslides can arise from the formation of

landslide dam A landslide dam or barrier lake is the natural damming of a river by some kind of landslide, such as a debris flow, rock avalanche or volcanic eruption. If the damming landslide is caused by an earthquake, it may also be called a quake lake. Some ...

s, as at Thistle, Utah in April 1983. 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. It is seen on

submarine volcano Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. Many submarine volcanoes are located near areas of tectonic plate formation, known as mid-ocean ridges. The volcanoes at mid-ocean ridges ...

es as well as surface volcanoes: Kamaʻehuakanaloa (formerly Loihi) in the

Hawaiian–Emperor seamount chain The Hawaiian–Emperor seamount chain is a mostly undersea mountain range in the Pacific Ocean that reaches above sea level in Hawaii. It is composed of the Hawaiian ridge, consisting of the islands of the Hawaiian chain northwest to Kure Atoll, ...

and

Kick 'em Jenny Kick 'em Jenny (also: Kick-'em-Jenny or Mt. Kick-'Em-Jenny) is an active submarine volcano or seamount on the Caribbean Sea floor, located north of the island of Grenada and about west of Ronde Island in the Grenadines. Kick-'em-Jenny rises a ...

in the

Lesser Antilles Volcanic Arc The Lesser Antilles Volcanic Arc is a volcanic arc that forms the eastern boundary of the Caribbean Plate. It is part of a subduction zone, also known as the Lesser Antilles subduction zone, where the oceanic crust of the North American Plate is ...

are two submarine volcanoes that are known to undergo mass wasting. The failure of the northern flank of

Mount St. Helens Mount St. Helens (known as Lawetlat'la to the indigenous Cowlitz people, and Loowit or Louwala-Clough to the Klickitat) is an active stratovolcano located in Skamania County, Washington, in the Pacific Northwest region of the United St ...

in 1980 showed how rapidly volcanic flanks can deform and fail. Methods of mitigation of mass wasting hazards include: *

Afforestation Afforestation is the establishment of a forest or stand of trees (forestation) in an area where there was no previous tree cover. Many government and non-governmental organizations directly engage in afforestation programs to create forests a ...

* Construction of fences, walls, or ditches to contain rockfall * Construction of catchment dams to contain debris flows * Improved drainage of source areas *

Slope stabilization Slope stability analysis is a static or dynamic, analytical or empirical method to evaluate the stability of earth and rock-fill dams, embankments, excavated slopes, and natural slopes in soil and rock. Slope stability refers to the condition of i ...

References

External links

Georgia Perimeter College: Mass Wasting
* ttps://www.wfpa.org/forests-fish-law/steep-slopes/ WFPA: Steep Slopes: Geology, Topography, Storms and Landslides in Washington State
NPS.gov: Mass Wasting
{{DEFAULTSORT:Mass Wasting Environmental soil science Geological hazards Geomorphology