Download Mass Movements

Mass Movements
Section 5.3
Pages 143-147
Mass Movements
• Mass movement: The transfer of rock
and soil downslope due to gravity
• Triggered by:
– Water
– Oversteepened slopes (stable angle slopes
are 25-40 degrees)
– Vegetation loss or removal
– earthquakes
How Mass Movements are
classified
• Classified by:
– The kind of material that moves
– How it moves
– Speed of movement
Types of Mass Movements
• FIVE types:
– Rockfalls
– Slides
– Slumps
– Flows
– Creeps
Types of MM:
• Rockfalls: rocks fall through the air; rocks
fall off steep slopes
• Slides: blocks of material move suddenly
along a flat, inclined surface
– Rockslide: slides that include segments of
bedrock; fastest MM; often triggered by rain or
melting snow
Types of MM cont’d:
• Slumps: downward movement of a block
of material along a curved surface; slow
moving; leave crescent shaped cliff
• Flows: contain large amt of water; moves
downslope as a thick fluid
– Mudflow: mixture of soil, rock, water- like
concrete
– Earthflow: move slowly- may take years
Types of MM cont’d:
• Creep: slowest; freezing/thawing cycles
expands water and lifts soil particles;
usually not witnessed