1. Soil Formation and
Mass Movements

2. How does water cause mass movements?
Bellwork: Pg
How does water cause mass movements?
How do earthquakes cause mass movements?

3. Climate determines soil formation

4. Soil Formations
Tropical Climate
Dry Climate
Temperate Climate

5. Tropical
Tropical (wet and warm) Climates make Laterite soils that are thick and infertile

6. 1. Tropical
Rain washes away the A Horizon, but rotting vegetation covers the B Horizon

7. Laterite

8. 2. Desert
Desert (Dry) climates make soils from mechanical weathering
Soil is thin and mostly of parent rock (regolith)

9. 3. Temperate
Temperate (cool to warm) climates make 2 soils that depend on rainfall.
Rain fall is not excessive

10. 3. Temperate Pedalfer Soils – more than 65 cm of rain per year
ex: clay, quartz, iron
b. Pedocal Soils –less than 65 cm of rain per year
ex: calcium carbonate

11. Pedalfer

12. Pedocal

13. Mass Movements

14. Mass Movements Definition
The transportation of rock and soil down slope due to gravity
Talus: a pile of rock fragments that accumulates at the base of the slope

16. Together, weathering and mass movements produce most landforms
Streams and valleys are the most common landforms on earth

17. Why?
Most mass movements end up in a stream or valley

18. Triggers of Mass Movements
Water – heavy rain and snow saturate the ground

19. Triggers of Mass Movements
2. Oversteepened Slopes – angles 25 to 40 degrees will hold loose particles. If a slope is steeper than 40 degrees, slips become more likely.

20. Triggers of Mass Movements
3. Removal of Vegetation – plant roots attempt to stabilize
4. Earthquakes

21. Classification of Mass Movements
Mass movements are based on 3 things:
Type of material that moves
How it moves
Speed of movement

22. Types of Mass Movements…

23. 1. Rockfall: rocks or fragments fall freely through the air =fast movement
Common on steep slopes & can trigger other mass movements

24. 2. Slide: material moves suddenly along flat, inclined surface

25. Rockslide: slides including segments of bedrock

26. Hinsdale County, Colorado 700 years old and still moving
Slumgullion landslide
Hinsdale County, Colorado
700 years old and still moving

27. 3. Slump: downward movement of material along a curved surface
Leaves a crescent-shaped cliff

28. A slump is a type of slope failure which involves the rotational movement of soil or rock

30. 4. Flows: materials containing large amounts of water

31. Earthflow – moves slowly
Mudflow – moves quickly

32. 5. Creep: slowest type of mass movement. (freezing & thawing)