Types of Mass Movements
Mass Movement:
Mass movement is dependent on the development of instability on a hill slope when equilibrium has been disturbed.
Safety Factor is a measured by ratio of resistance which the slope offers against movement (sheer STRENGHT) to the force which is trying to enact that movement (sheer STRESS)
Factors affecting Sheer STRESS 1) Angle /Steepness of Slope: Inclination of slope will affect the magnitude of gravitational force enacting on the regolith. a. the larger the angle of inclination, the greater the magnitude of gravitational force b. mass movement when magnitude of gravitational force is able to overcome the frictional force opposing the motion of the regolith 2) Weight of regolith: the greater the weight of regolith the greater the magnitude of gravitational force
Note: Because gravitational force is stronger on steeper slopes, regoliths are pulled down faster, consequently, regoliths on steep slopes is likely to be thinner.
Factors affecting Sheer STRENGHT 1) Nature of slope –Shape and size of particles: a. A slope made up of large angular rocks is more stable than a slope made up of small circular rocks This is because larger rocks have a greater ANGLE OF REPOSE 2) Nature of slope-type of particles: clay and slit particle, sand v.s. snow (unstable) b. Slopes made up of sand and gravels has more friction and hence higher sheer strength c. Clay and slit are cohesive i. Mayback fire since retention of water increases weight d. Dependent on moisture – too much or too little decrease sheer strength e. Greatest internal strength due to effect of solidification and crystalisation which creates extremely strong chemical and physical bonds 3) Nature of slope – Ground cover f. Roots of vegetation hold loose material together reduces transportation.
Water Content
Encourages mass movement by increasing Sheer Stress and decreasing Sheer Strength
Period of
Mass movement is dependent on the development of instability on a hill slope when equilibrium has been disturbed.
Safety Factor is a measured by ratio of resistance which the slope offers against movement (sheer STRENGHT) to the force which is trying to enact that movement (sheer STRESS)
Factors affecting Sheer STRESS 1) Angle /Steepness of Slope: Inclination of slope will affect the magnitude of gravitational force enacting on the regolith. a. the larger the angle of inclination, the greater the magnitude of gravitational force b. mass movement when magnitude of gravitational force is able to overcome the frictional force opposing the motion of the regolith 2) Weight of regolith: the greater the weight of regolith the greater the magnitude of gravitational force
Note: Because gravitational force is stronger on steeper slopes, regoliths are pulled down faster, consequently, regoliths on steep slopes is likely to be thinner.
Factors affecting Sheer STRENGHT 1) Nature of slope –Shape and size of particles: a. A slope made up of large angular rocks is more stable than a slope made up of small circular rocks This is because larger rocks have a greater ANGLE OF REPOSE 2) Nature of slope-type of particles: clay and slit particle, sand v.s. snow (unstable) b. Slopes made up of sand and gravels has more friction and hence higher sheer strength c. Clay and slit are cohesive i. Mayback fire since retention of water increases weight d. Dependent on moisture – too much or too little decrease sheer strength e. Greatest internal strength due to effect of solidification and crystalisation which creates extremely strong chemical and physical bonds 3) Nature of slope – Ground cover f. Roots of vegetation hold loose material together reduces transportation.
Water Content
Encourages mass movement by increasing Sheer Stress and decreasing Sheer Strength
Period of