Mass Movements. Mass movement- The down slope movement of earth material under the influence of...
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Transcript of Mass Movements. Mass movement- The down slope movement of earth material under the influence of...
In order for the material to move down slope, it must overcome
1. Friction –surface resistance to relative motion.
2. Inertia – tendency of an object at rest to remain at rest.
2. Pyroclastic materials – Light colored tuff from Santorini produced 3500 year ago in Minoan eruption.
Internal problems caused by water1. Adds weight to a slope
8.34 lb/gallon 54 gal. = 457.36 lb!
54 gal.barrel
Some Factors Leading to Slope Failure1. Valley is a syncline2. Cavernous weathering of limestone rock3. Valley downcutting by river4. Slope saturation - water from reservoir and heavy rains.
Translational slide – landslide1. Mass moves
down and out.2. Moves far and
fast.3. Primary causes:
heavy rains or earthquakes.
Earthflow- Downslope movement of a fluid layer of mainly soil and weathered rock material that is saturated with water.
Key differences between earthflows and debris flows:
1. A debris flow moves faster; meters/second.2. A debris flow carries larger rock material.
Debris flows can carry large boulders because their density is 1.5 – 2.0 times that of water.
http://www.youtube.com/watch?v=8mKC3eID074
Causes of debris flows:
1. Most commonly heavy rains or rapid snow melt.
2. Volcanic eruptions – a lahar is a type of debris flow.
3. Earthquakes
• Debris avalanches http://www.youtube.com/watch?v=QOUH4daO4-4
http://www.youtube.com/watch?v=BKTG58Bpziw&feature=fvwrel
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.
Sturzstroms- Long-run out debris flows.
Blackhawk sturzstrom 300 million m3
Drop .75 mi. Flow 5.6 mi.
1970 subduction zone earthquake
100 million m3 of rock, ice glacial sediments, and water.
Speed 175 - 210mph
Devastated area 8.7 mi2
18,000 deaths
What kind of movement is this?
• http://www.youtube.com/watch?v=ZVYGJYnJTi0&feature=related