Mass movement, often called mass wasting, is the downslope movement of a mass of surface materials, such as soil, rock or mud. This mass movement typically occurs
along hillsides and mountains
due to the influence of gravity and can happen very slowly or very quickly.
Where does mass movement usually occur in general?
They usually occur at
very steep slopes such as a cliff face
. The rock material may be loosened by earthquakes, rain, plant-root wedging and expanding ice, among other things. The accumulation of rock material that has fallen and resides at the base of the structure is known as talus.
Where do rapid mass movements occur?
In rapid mass movements, perceptible motion occurs. The events are briefer in duration, more damaging, and occur
on relatively steep slopes
. Produced by rocks falling from near vertical cliffs, the rockfall is the smallest, most common, and most rapid from of mass wasting.
What can trigger a mass movement?
Such factors include:
weathering or erosional debris cover on slopes
, which is usually liable to mass movement; the character and structure of rocks, such as resistant permeable beds prone to sliding because of underlying impermeable rocks; the removal of the vegetation cover, which increases the slope’s susceptibility …
What are the 4 main mass movements?
- 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.
Which type of mass movement is the fastest?
Rockfalls
occur when rock fragments fall from steep cliffs. This is the fastest type of mass movement. The fragments may be as tiny as pebbles or as huge as giant boulders.
How do humans affect mass movement?
Humans can contribute to mass wasting in a few different ways:
Excavation of slope or its toe
.
Loading of slope
or its crest. Drawdown (of reservoirs)
What is the most important factor in causing mass movements?
Gravity
is the main force responsible for mass movements. Gravity is a force that acts everywhere on the Earth’s surface, pulling everything in a direction toward the center of the Earth.
What are examples of mass movement?
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. Often lubricated by rainfall or agitated by seismic activity, these events may occur very rapidly and move as a flow.
How can we prevent mass movement?
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.
What is the slowest type of mass movement?
The slowest type of mass movement is
creep
. This occurs on slopes where there is significant plant or tree growth.
Which mass movement is the most destructive?
The most destructive type of mass movement is
a landslide
, which occurs when rock and soil slide quickly down a steep slope. Some landslides may contain huge masses of rock, while others may contain only a small amount of rock and soil.
What force must be overcome in order for mass wasting to occur in most cases?
For mass wasting to operate on a sloped surface
the gravitational force
must be resolved into two vectors (Figure 7). One must be the downward force acting perpendicular to the sloped surface. This is the “Stay Force” component of the vertical pull of gravity.
What is fall in mass movement?
Types of mass movement
A fall or
topple happens when rocks and other sediments fall through the air and land at the bottom of a slope
. Falls and topples. Flows are a mixture of water, rock and sediment. They move very quickly.
What are the six types of mass movement?
Types of Mass Movement:
Creep; Fall, Slip, Flow; Solifluction
; Rock Glaciers; Slumping (Earthflow); Mudflow (lahar); Debris Flow, Debris Slide, Debris Avalanche; Rockslide; Rockfall; Debris Fall.
What type of mass movement is flow?
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. Slump – involves movement along a curved surface, the upper part moving downward while the lower part moves outward.
