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