1. UNIT 4: Lithosphere – Mass Movements
LKQ3a What natural and man-made processes contribute to different types and causes of mass movements on slopes?
LKQ3b How are mass movements on steep and gentle slopes managed?

2. Guided Reading Questions
Explain the following rock weathering processes:
Mechanical weathering
Chemical weathering
Accumulation of debris on slopes
Describe the three basic types of rocks – igneous, sedimentary, metamorphic.
Explain the cause of mass movements and relate human activity or natural events to the following events:
Rock falls
Landslides
Earth slumps
Soil creep
Solifluction
Mudflows
Rotational slumping
What are some management policies including slope angle reduction, afforestation, drainage and surface protection?
List and explain some case studies (local) using examples from countries with contrasting levels of economic development. Examples should include Hong Kong, Rio de Janeiro, Sarno in Southern Italy, Himalayan Foothills, Sumatra (2009).

3. BELLRINGER: The Rock Cycle

4. GR #2

5. Types of Weathering GR #1 Mechanical Weathering
Breakdown of rock into smaller pieces by physical means
No chemical change
EX: ice, water, gravity, plants
Chemical Weathering
Chemical breakdown of rocks & minerals into new substances
EX: water, acid rain
Biological Weathering
Disintegration of rocks due to the actions of plants & animals

6. Climate Affects Rates of Weathering
Rate of Weathering
Hot and dry
Slow
Hot and wet
Fast
Cold and dry
Cold and wet

7. VIDEO: W.E.D

9. Changes to the Earth

10. LAB: Exploring Chemical Weathering

11. BELLRINGER: Factors Affecting Mass Movement
How does it affect mass movement?
Plate Tectonics
Geology
Gradient
Water
Vegetation

12. Mass Movement
the downslope movement of loose sediments and weathered rock resulting from the force of gravity
all occur on slopes
climate determines which materials and the quantity that are available for mass movement
range from fine mud to large boulders

13. Variables Influencing Mass Movements
Weight: gravity works to pull the material down a slope
Resistance: keep the material in place (friction, vegetation, barriers, etc.)
Trigger: works to shake material loose from a slope (an earthquake)
Water: too little water prevent sediment grains from holding together, too much water can act as a lubricant and make a slope unstable

14. Four Types of Mass Movement
FALLS
Movements of dry materials
Occur very quickly
Can create cones of material at base
EX: rock falls, land falls, cliff toppling
SLIDES
Movements of wet materials
Water creates slip-plane on which the material slides
EX: rotational slumps, transitional slides
CREEPS
Slow movements of moist earth & soil
Continue for hundreds of years
Terracettes (earth wrinkles form on slope surfaces
EX: soil creep, earth spreads
FLOWS
Very quick movements of loose material usually mixed w/water
Often seen during floods
Dangerous b/c of speed
EX: mudflow, debris flow

16. Project: Types of Mass Movements
GR #3
Project: Types of Mass Movements
Rock falls
Landslides
Earth slumps
Soil creep
Solifluction
Mudflows
Rotational slumping

17. Creeps
the slow, steady, downhill flow of loose, weathered Earth materials, especially soils
May be as little a few centimeters per year
Can be observed by the slow tilting of once-vertical poles, fences, and gravestones, the bending of trees, the cracking of walls, and the breaking of underground pipelines

18. Creep

19. Flows Earth materials flow as if they were a thick liquid
Earth flows – moderately slow movements of soil
Mudflows - swiftly moving mixtures of mud and water
Can be triggered by earthquakes or other vibrations and are common in volcanic regions

20. Mudflows after the 1980 eruption of Mount St
Mudflows after the 1980 eruption of Mount St. Helens traveled downhill at over 30km/hr and destroyed over 200 homes

21. Mudflows are also common in sloped semi-dry regions that experience short, intense rain storms like southern California

22. Landslides
Landslide – a rapid, downslope movement of Earth materials that occurs when a relatively thin block of loose soil, rock, and debris separates from the underlying bedrock
can reach speeds of 200km/hr
Eventually stops and becomes a pile of debris

23. Landslide

24. Landslide

25. Rock slide – type of landslide when a sheet of rock moves downhill on a sliding surface

26. Slumps
Results when a mass of material in a landslide rotates and slides along a curved surface
Common on extremely steep slopes and after rains

27. Slump

28. Avalanche
Landslides that occur in mountainous areas with thick accumulations of snow
Can reach speeds of 300 km/hr
About 10,000 avalanches occur each year in the western US alone

29. Avalanche

30. Human Effects on Landslides
Human activities such as building heavy structures on slopes and water leaking underground contribute to mass movements
The best prevention is not to build on slopes
Short term preventions include covering slopes with steel nets and constructing protective fences and walls

31. Management Policies GR #4 Management Policy What is it?
How Does it Help?
Slope Angle Reduction
Afforestation
Drainage
Surface Protection

33. How can slopes be stabilized?
Plant vegetation: bind the soil together and intercept rainfall
Improve Drainage: prevent the slope from becoming saturated and stops lines of weakness for example bedding planes becoming lubricates
Equipment: use wire nets and metal stakes to hold slope together
Reduce the gradient: adding material to the base of a slope

34. Management Policies: Slope Angle Reduction
identification of area prone to landslides due to a steep slope
soil can be moved in to reduce the grade (angle) to try and prevent the likelihood of mass movements along them
If an area has been cut away, bringing in land to fill the void may also take much of the risk of mass movement away.

35. Management Policies: Afforestation
planting trees and vegetation in areas where currently none grows
stabilize the land by providing leaf litter and root structure
reforestation is the process of reclaiming a land to it original state, one it is found that be deforesting, it is susceptible to mass movements
replanting trees can increase drainage into the ground and prevent water from eroding the soil away
trees provide transpiration, which is how they soak up the water and evaporate it back in the air

36. Management Policies: Drainage
set up drainage systems to divert water away from slopes and into established waterways
making troughs in the land that divert the water away or with pipes that bring the water around the areas in danger

37. Management Policies: Surface Protection
areas may be covered with vegetation or other natural material (like mulch) in order to protect it from flowing water or air
be the easiest measure to protect against mass movement
must be replenished at certain intervals if the material is just sitting on the ground, rather than planted in it

38. As human populations expand and occupy more and more of the land surface, mass movement processes become more likely to affect humans. The table below shows the impact of mass movement processes on human life over the last century.