Classifications of Mass Wasting:
Four Main Types of Mass Wasting:
Flow
Flows are a mixture of water, rock and sediment. They move very quickly. Large flows can bury entire villages. Smaller flows can block roads.
Shear occurs throughout the moving mass and there is no well-defined shear plane. The shear is maximum at base of flow.
Some volcanoes are covered with snow and ice. If they erupt, melted snow and ice mixes with mud and volcanic ash and flows down mountain. Volcanic flows are called lahars.
Shear occurs throughout the moving mass and there is no well-defined shear plane. The shear is maximum at base of flow.
Some volcanoes are covered with snow and ice. If they erupt, melted snow and ice mixes with mud and volcanic ash and flows down mountain. Volcanic flows are called lahars.
Creep/Heave
Creep is a very slow mass movement that goes on for years or even centuries. Creep is nearly imperceptible to the naked eye as it is the slowest of all types of mass movement. Soil creep generally occurs in the top few meters of the surface and is accomplished by expansion and contraction of the soil. For instance, when water in the soil freezes the ice pushes soil particles outward perpendicular to the slope. Upon warming, the ice melts and the soil is pulled down slope under the influence of gravity. Over many freeze-thaw cycles soil moves slowly down slope. In many cases one might not be able to tell that soil creep is occurring by just examining the surface. However, trees growing on surfaces undergoing creep will have curved trunks or roots that are curved. Broken retaining walls and curved railroad tracks also indicate creep in action.
Slide
A slide is a sheet of material that slips over a failure plane ending anywhere from a meter to a kilometer down slope. Slides produce concave scars while slumps tend to produce a scarp or cliff exposure. Trees are broken and bent and the slide can bury the soil down slope. Digging into buried soils and analyzing their contents can tell us about the age and what the environment was like when the slide occurred.
A slide happens when a section of soil or rock suddenly gives way and moves down a slope. The material moves as a single mass along a slippery zone. The slippery zone is often made up of wet sediment.
La Conchita, California has experienced devastating landslides in recent years. Unstable slopes mobilized by rain water caused a landslide and debris flow. The city lies on a narrow strip of coast 250m (800ft) wide between the shoreline and a 180 m (600ft) bluff above it. Extraordinary rains and rising groundwater levels caused the slope to fail, fortunately no one was killed. However, in 2005, another year of abnormally high rain fall caused the slope to fail again, this time burying structures and killing 10 people. The images below are examples of the aftermath of such landslides.
A slide happens when a section of soil or rock suddenly gives way and moves down a slope. The material moves as a single mass along a slippery zone. The slippery zone is often made up of wet sediment.
La Conchita, California has experienced devastating landslides in recent years. Unstable slopes mobilized by rain water caused a landslide and debris flow. The city lies on a narrow strip of coast 250m (800ft) wide between the shoreline and a 180 m (600ft) bluff above it. Extraordinary rains and rising groundwater levels caused the slope to fail, fortunately no one was killed. However, in 2005, another year of abnormally high rain fall caused the slope to fail again, this time burying structures and killing 10 people. The images below are examples of the aftermath of such landslides.
Fall
Falls are usually the free-fall of pieces of rock from a mountain or cliff face. The size of the piece(s) can range from tiny grains to blocks weighing a ton or more. The debris and rock fragements from rock falls collect at the base of the slope as talus. This talus protects the base of the mountain from erosion. On mountains, ice wedging is the main contributor. As water from snowmelt finds its way into the cracks and joints of the rock face, it may refreeze and being to expand. This expansion widens the cracks in the rock. Over time, the cracks have been widened enough so that they are a point of structural weakness. Gravity takes over and the pieces of rock fall from the face of the mountain.