1. The process by which sediments are obtained and transported.
EROSION
The process by which sediments are obtained and transported.
Erosion involves a transporting system with several components:
AGENT OF EROSION- (e.g. stream, glacier, wave, current, wind, or human activity).
2. SEDIMENTS BEING MOVED
3. DRIVING FORCE

2. The DRIVING FORCE behind most types of EROSION is
GRAVITY

3. Mass Wasting
The downward movement of material under the influence of gravity is called mass wasting.
Water can play an important role, but gravity is the main element

4. MASS WASTING INVOLVES TWO MAJOR OPPOSING FORCES
1. FORCE OF GRAVITY – constant downward pull
2. FORCE OF FRICTION – attempts to keep objects in place
Gravity > Friction – movement
Gravity < Friction – no movement
Gravity = Friction (equilibrium) – no movement

5. Oh no!

6. Factors that resist gravity include
the materials strength and cohesion
vegetation
internal friction between grains
Angle of underlying rock
Factors that help gravitational forces
increasing the slope angle
under cutting of the slope
amount of weathering
amount of water moving through material
overloading slopes with new material

7. Mass wasting is often caused by a force that temporarily disturbs the slope equilibrium
Earthquakes
Heavy rain
Leakage from water pipes and swimming pools
Volcanic eruptions
explosions
thunder

8. Excavation at the base of a slope can lead to slope instability
i.e. road cut along slopes

9. The angle at which the underlying rock is inclined has a major impact on mass wasting.

11. Slides:
These are slow to rapid movement of material along one or more surfaces.
Slumps are Usually slow to moderate in speed
Movement along a curved surface
Usually in unconsolidated materials like soil
Rockslides are rapid to very rapid
movement along a planar surface

12. A Slump

13. Slump caused by erosion in southern California

14. This is called, (you guessed it), a Rock Fall
Mass wasting occurs when rocks weather at a higher elevation and fall to a lower elevation.
This is called, (you guessed it), a Rock Fall

15. Rock Falls: Free falling rock from steep mountain sides
Rock Falls: Free falling rock from steep mountain sides. Usually caused by ice wedging.
Any sized material may fall. The collected debris at the bottom is called TALUS

16. Talus Slope or Rock fall

18. In real life, landslides can be quite destructive:
Rate = 1 mm/day to 1 km/hr
Houses can be totally covered by sand and mud, like this:

19. This landslide tragically took the life of many unsuspecting woodland creatures.

20. Types of landslides

21. Flows:
These are mass movements where the material moves as a viscous fluid or plastic movement
Mudflows are very rapid and contain a lot of water and mud
Earthflows are slow to moderate movement of material down a slope which leaves an exposed scrape.
Solidification is the slow downward movement of water saturated soil. Common in areas of permafrost
Creep is extremely slow movement of soil & rock downhill

22. Mud Flows happen faster (1-5 km/hr)
THE PROBLEM WITH LANDSLIDES AND MUDSLIDES IS THAT THEY ARE OFTEN UNPREDICTABLE AND CAN BE VERY DAMAGING TO LIFE AND PROPERTY

24. Mud Flow

25. Solidifluction: in Alaska

26. Soil creep “Soil creep” happens very slowly (less than 1 cm per year).
Soil gradually moves downhill

27. Bent trees are the most obvious indicator of soil creep

28. Creep

29. Solutions to Mass wasting:
Surface and subsurface drainage of hillsides
Replanting of vegetation
Reduce the angle of slope
Putting in retaining walls and bolting rock faces