Describe the Picture: Use 5 observations (things you see) and 3 inferences
(conclusions drawn from knowledge)
Essential QuestionsWhat are mass movements?
What factors trigger mass movements?
Mass movements What is it?
movements of masses of bodies of soil, bed rock, rock debris, soil, or mud
usually occur along steep-sided hills and mountains
due to the pull of gravity
Seen as landslides, mud slides, and avalanches
Mass movements
What are the triggers of mass wasting? Infer two triggers of mass wasting
(besides water) Turn to a neighbor and discuss the
triggers you inferred
Mass movement triggers Triggers
Water saturationOversteepening of slopesRemoval of vegetationEarthquakes
Types of Movements Rockfalls Slides Slumps Flows Creep
Mass Movements Rockfalls
Occurs when rocks fall freely
Common on slopes that are too steep to retain loose materials
Frequently caused by frost-wedging British Columbia, Canada. (- Geoscape
Vancouver
Mass Movements Slides
Blocks of material move suddenly down flat, inclined surface
Exp: rock slidesOne of the fastest
mass movements The rock slide at Frank, Alberta, Canada (1903) moved 33 million m3 of rock from Turtle Mountain over the town of Frank in less than two minutes killing 70 people, NOAA
Mass Movements Slumps
Downward motion of block of material along curved slope
Not a large change in distance or fast
Common on oversteepened slopes with thick accumulations of clay
Berkeley, CAhttp://geology.about.com/od/naturalhazardsclimate/ig/Landslides/berklandslide1.htm
Mass Movements Flows
mass movements of material containing large amounts of water > move as thick fluids
Mudflows-can move up to 80 km/h○ Common in
semiarid mountainous regions
Mount St. Helen, WAhttp://www.sfu.ca/geog/geog351fall06/group06/Landslide1980.htm
Mass Movements Flows
Earthflows○ move 1 mm/day to
several meters/day○ Occur on hillsides in
wet regions○ Creates tounge-
shaped mass http://www.webpages.uidaho.edu/~simkat/cors220_files/lecture11.html
Mass Movements Creep
Slowest typeMoves few mm-
few cm/ yearFreezing and
thawing contributes to creep
Cause structures to tilt
Writing Assignment: What is the impact of mass movements
on the social and economic status of an area?
Yungay, Peru before and after landslidehttp://www2.fiu.edu/~longoria/natural/mass/mmain.htm