Mass movement
What is mass movement?
The general term for the downward movement of a section of land down a slope.
Two examples of rapid mass movements
Rockfall, landslide, mudflow
What is slow mass movement?
The downward slope of material down a slope over a long period of time.
The sudden movement of rock and soil down a slope.
Landslide
The rapid movement of a large mass of mud.
Mudflow
Three examples of mass movement.
rock fall, landslide, mudflow, soil creep
What is a rock fall?
A group of loose rocks that fall down a steep slope
What is a creep?
The downhill movement of weathered rock material.
A landslide in which material moves along a curved surface.
Slump
What is Lahar?
Mudflow of volcanic origin
The main force that causes all mass movement.
Gravity
List three (3) ways to prevent mass movement
Slope dewatering
Slope reduction
Building stabilizing structures
List at least three (3) individual measures to reduce the damage of mass movement
•Reinforce the house foundation and the walls of vulnerable areas
•Install good pipes to avoid gas or water leaks in the event of mass movement
•Evacuate immediately when warned
•Do not return until the proper authorities declare that it is safe to do so
•Keep emergency supplies such as food, water, ropes, buckets, flashlights, a portable radio and a first aid kit
Factors that increase the chances of a landslide
earthquakes, heavy rains, deforestation and construction on unstable slopes.
Areas where mudflows are common.
Mountainous regions
The most destructive kind of mass movement
Rapid mass movement
Occur on steep slopes exceeding 40°
Rockfalls
Ways water contributes to creep.
Water loosens soil and allows it to move freely
Faster than an earthflow and occurs on steeper slopes
Mudflow
Explain two causes of mass movement
•Mudflows can occur when the snow or ice cover of a volcano melts and mixes with the soil to form mud
•When water accumulates quickly in the ground, such as during heavy rainfall or rapid snowmelt, the earth can become a river of mud
•Earthquake tremors can cause sections of mountains or hills to break off and move down slope
•Human activities alter the vegetation cover and loosen the soil, making the earth more prone to mass movement
•Vibrations from machinery and traffic, and weight loading from accumulation of snow and stockpiling of ore can trigger mass movement