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Mass wasting

earth science Maturity 9-11 Next article →

Mass wasting, also called mass movement, is a geological process where rock and soil move down a slope. This movement is driven by the force of gravity. It is a specific type of erosion. In other erosion processes, a moving medium like wind, water, or ice carries the debris. In mass wasting, the material is not entrained in such a medium. While water often helps the process, it is not abundant enough to act as the main transporter. This creates a thin line between a mudflow and a very muddy stream.

Mass Waste Palo Duro 2002
Mass Waste Palo Duro 2002

Mass wasting can be classified by how the material moves. One major category is creep. Soil creep is a slow, long-term movement. Gravity pulls soil or rock gradually downslope through small movements in different directions. The steeper the slope, the faster this creep occurs. It can cause trees to grow with curved trunks as they try to stay upright. It can also tilt fences or telephone poles. Over time, this movement can form terracettes on the surface.

Grand mesa creep
Grand mesa creep

Another type of slow movement is solifluction. This is a specific form of creep found in arctic or alpine climates. It occurs on moderate slopes that are mostly free of vegetation. These slopes are underlain by permafrost, which is ground that stays frozen. During the summer, the top layer of soil thaws and becomes saturated with moisture. This wet soil then creeps downhill. Solifluction can create large landforms like stone rivers or terrace-like shapes.

Thistle 2010 from US6 rest area
Thistle 2010 from US6 rest area

Landslides represent a much faster type of mass wasting. A landslide is the rapid movement of a large mass of earth and rocks down a mountainside. These can be classified by how much water is involved. A landslide might involve relatively dry debris on steep slopes. As water content increases, the movement becomes a debris avalanche. With even more water, it becomes an earthflow or a mudflow. If the water content increases further, it becomes a sheetflood, which is actually a form of sheet erosion.

GCRockfall
GCRockfall

There are different causes for these movements, divided into passive and activating causes. Passive causes are permanent conditions that make a slope susceptible. These include steep topography, weak rock lithology, or faults that weaken the ground. A lack of vegetation also makes a slope less stable. Activating causes are events that trigger the movement. These include earthquakes, increased soil moisture, or the weight of new structures. Even undercutting a slope through excavation can start a slide.

TalusConesIsfjorden
TalusConesIsfjorden

Mass wasting is a common phenomenon throughout our Solar System. It occurs on both terrestrial and submarine slopes on Earth. Submarine mass wasting is common along coastlines where glaciers are retreating. These underwater slides can move huge volumes of sediment over hundreds of kilometers in just a few hours. Scientists have observed mass wasting on Mars, Venus, and Jupiter's moon Io. It has also been seen on Triton. It may even occur on Europa and Ganymede.

TalusConesIsfjorden
TalusConesIsfjorden

These events can have serious consequences for humans and the environment. Rapid landslides can be deadly and destructive. In March 2014, a landslide in Oso, Washington, resulted in 43 fatalities. Landslides can also create landslide dams, as seen in Thistle, Utah, in 1983. They pose challenges to civil engineering by breaking pipelines or displacing roads. To mitigate these hazards, engineers use several methods. They might use afforestation to grow trees for stability. They also build walls, catchment dams, or improved drainage systems to control the movement.

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File:TalusConesIsfjorden.jpg
TalusConesIsfjorden.jpg
File:Mass Waste Palo Duro 2002.jpg
Mass Waste Palo Duro 2002.jpg
File:GCRockfall.JPG
GCRockfall.JPG
File:Grand mesa creep.jpg
Grand mesa creep.jpg
File:Thistle 2010 from US6 rest area.JPG
Thistle 2010 from US6 rest area.JPG
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