Water seeps into cracks in rocks, freezes, and expands, causing further breakdown of rocks. Biological weathering is caused by plants and animals and also contributes to the breaking down of rocks and landforms. These weathering processes cause rocks and landforms to fragment, crack, and breakdown.

Weathering is the physical disintegration or chemical alteration of rocks at or near the Earth‟s surface. Erosion is the physical removal and transportation of weathered material by water, wind, ice, or gravity. Mass wasting is the transfer or movement of rock or soil down slope primarily by gravity.

Once rock material has been broken down into smaller, unstable pieces by weathering, the material has the potential to move down slope called mass wasting (also called a mass movement or a landslide) because of gravity. The steeper the slope, the greater potential for gravity to pull objects down.

There are four different types of mass movement:

• Rockfall. Bits of rock fall off the cliff face, usually due to freeze-thaw weathering.
• Mudflow. Saturated soil (soil filled with water) flows down a slope.
• Landslide. Large blocks of rock slide downhill.
• Rotational slip. Saturated soil slumps down a curved surface.

Mass wasting is the movement of rock and soil down slope under the influence of gravity. Rock falls, slumps, and debris flows are all examples of mass wasting.

The slowest type of mass movement is creep. This occurs on slopes where there is significant plant or tree growth.

Falls are abrupt movements of masses of geologic materials, such as rocks and boulders, that become detached from steep slopes or cliffs. Separation occurs along discontinuities such as fractures, joints, and bedding planes, and movement occurs by free-fall, bouncing, and rolling.

Mass Movement Types

c) Slides: A slide is the downslope movement of a soil or rock mass occurring dominantly on the surface of rupture or relatively thin zones of intense shear strain. d) Flows: A flow is a spatially continuous movement in which shear surfaces are short lived, closely spaced and usually not preserved after the event.

Gravity

Mass movements affect the following elements of the environment: (1) the topography of the earth’s surface, particularly the morphologies of mountain and valley systems, both on the continents and on the ocean floors; (2) the character/quality of rivers and streams and groundwater flow; (3) the forests that cover much …

Mass movement control must be primarily preventive: e.g., mapping vulnerable zones, drawing up a land use plan, banning building work or any modification of slopes, and protection in the form of coppice forests.

Human activity is one of the causes of mass movement. Increased human activity would increase the driving forces of mass movement. The density of the human activity, such as infrastracture, plus the pull of gravity would increase the likelihood of a landslide or a mudslide, or weaken a part of the slope.

Movement by mass wasting can be slow or rapid. Rapid movement can be dangerous, such as during debris flows. Areas with steep topography and rapid rainfall, such as the California coast, Rocky Mountain Region, and Pacific Northwest, are particularly susceptible to hazardous mass-wasting events.

Creation of lakes. Mounds of debris or blocks of rocks have dammed river courses creating temporary lakes. Areas affected by mass wasting have become centres of research and study on the dynamics of stability of the earth layers.

Types of mass wasting include creep, slides, flows, topples, and falls, each with its own characteristic features, and taking place over timescales from seconds to hundreds of years.

Mass wasting – is movement in which bed rock, rock debris, or soil moves downslope in bulk, or as a mass, because of the pull of gravity. Flow – The debris is moving downslope as a viscous fluid. A mudflow is a flowing mixture of debris and water, usually moving down a channel.

Engineering solutions include barriers and retaining walls, drainage pipes, terracing the slope to reduce the steepness of the cuts, and immediate revegetation. Rockfalls can be controlled or eliminated by the use of rock bolts, cables, and screens and by cutting back slopes to lesser gradients.

Debris flows differ from slides because they are made up of “loose” particles that move independently within the flow. A slide is a coherent block of material that “slides” over a failure surface. Debris flows have larger particles – at least 50% of a debris flow is made up of sand-size or larger particles.

It’s lumpy, lobe-shaped, and rocky. It’s muddy, lobe-shaped, and smooth. It has scarps near the top and a rounded, lumpy lower end.