Mass Movements. Mass movement - The down slope movement of earth material under the influence of gravity. Figure 10.3. Key role in mass movement is gravity. In order for the material to move down slope, it must overcome Friction –surface resistance to relative motion.
Mass movement- The down slope movement of earth material under the influence of gravity.
Key role in mass movement is gravity
Inherently weak earth materials
Internal problems caused by water
1. Adds weight to a slope
54 gal. = 457.36 lb!
Low pore water pressure High pore water pressure
Vaiont, Italy 1963
Setting: Dam on river in a glacially carved canyon.
Earthflow- Downslope movement of a fluid layer of mainly soil and weathered rock material that is saturated with water.
Usually, like slumps, they do not move very fast.
Debris flow- Downslope movement of a fluid mixture of mud and larger rock debris.
Debris Avalanche- A very fast moving debris flow occurring on steep slopes.
2005 debris avalanche
Small mass movements usually move horizontally less than twice their vertical distance of fall.
With very large mass movements they may move up to 25 times the distance of their vertical fall.
Blackhawk sturzstrom 300 million m3
Drop .75 mi. Flow 5.6 mi.
100 million m3 of rock, ice glacial sediments, and water.
Speed 175 - 210mph
Devastated area 8.7 mi2