1. Use the map to answer the question.
                
       Louisiana has lost and gained land on its coast over the years. The red color on the map shows the land gained in Atchafalaya Bay between the years 1932 and 2000. What caused the new land to form?
A.sediments moved by waves
B.tectonic uplift
C.sediments carried by rivers
D.dropping sea levels

2. Mass Movements at Earth’s Surface
Pg. 75

3. Mass movements
The downslope movement of loose sediments and weathered rock resulting from gravity
Weathering  erosion  mass movements
Climate controlled
All occur on slopes

4. Influencing variables
Material’s weight
Resistance to sliding or flowing
A trigger event (ex. Earthquake)
Erosion at the foot of a slope
water

5. Water and mass movements
Too little prevents sediments from holding together, increasing potential for movement
Too much water increases the weight of the soils; can also act as a lubricant
Not involved as transport agent

6. Types of mass movements
Classified as:
Creeps
Flows
Slides
Falls
Slumps
Avalanches

7. Creeps Slow, steady downhill flow of soils
Noticeable over long periods
Observe structures to identify creeps
Solifluction occurs when layer above permafrost slides downhill

8. Flows Flow as if the mass was a thick liquid Can move fast or slow
Mudflows-swiftly moving mixtures of mud and water
Common in volcanic regions
Also common in semi-arid regions that experience intense short rainstorms (So Cal)

9. Slides Rapid, downslope movement of earth’s materials
Happens when a thin block of loose soil, rock, and debris separate from the bedrock (landslide)
Can cause flooding
Common on slopes that are water saturated
Rock slides are triggered by earthquakes

10. Slumps
When material in a landslide rotates and slides along a curved surface
Occur in areas with thick soils and steep to moderate slopes
Common after rains
Leave crescent shaped scars

11. Avalanches Landslides that occur in mountainous areas with snow
Usually occur on slopes of at least 35 degrees
10000 avalanches occur every year in west US alone
Sun melts surface snow  refreezes over night loose snow accumulates  becomes heavy and slips off
Snow refreezes into crystals  vibrations send the layer down slope

12. Rock Falls
Occur at high elevations, in steep road cuts, and rocky shorelines
Rock breaks and falls downward
Produces a cone shaped pile of debris called talus
Less likely to occur in humid regions

13. Mass movements and people
Constructing heavy buildings and roads and poor maintenance of sewer systems can result in mass movements
Venezuela 1999 experienced heavy rains which resulted in severe mudflows killing tens of thousands of people
Can be avoided by not building structures on steep slopes
Trenches can be dug to divert water