1. Mass Movements Earth Science V1 .pptx

Mass movement

1. Chapter 8 Section 1 Earth Science

2. What is the relationship between gravity and mass movements?

3. How do mass movements affect people?

4. Mass Movements Copyright © McGraw-Hill Education Mass Movements The downslope movement of soil and weathered rock resulting from the force of gravity is called mass movement .. All mass movements occur on slopes. Because few places on Earth are completely flat, almost all of Earth’s surface undergoes some degree of mass movement.

5. Factors Affecting Slope Stability Type of earth material Slope angle and Topography Climate Vegetation Water Time

6. Triggers for rapid Mass Wasting Rain Oversteepening Cutting at the foot of slope Piling on head of slope Deforesting/ Devegetating Earthquakes

7. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Creep The slow, steady, downhill flow of loose, weathered Earth materials, especially soils, is called creep . The effects of creep are usually noticeable only over long periods of time.

8. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Creep One way to way to tell whether creep has occurred is to observe the positions of structures and objects.

9. Creep Very slow downward slope movement of soil Result of freezing and thawing

10. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Flows Earth flows are moderately slow movements of soils, whereas mudflows are swiftly moving mixtures of mud and water. Mudflows can be triggered by earthquakes or similar vibrations.

11. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Flows Lahars are mudflows that occur in volcanic regions where the heat from a volcano melts snow on nearby slopes that have fine sediment and little vegetation. Mudflows are also common in sloped, semi-arid regions that experience intense, short-lived rainstorms.

12. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Slides A rapid, downslope movement of Earth materials that occurs when a relatively thin block of soil, rock, and debris separates from the underlying bedrock is called a landslide .

13. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Slides Landslides are common on steep slopes, especially when soils and weathered bedrock are fully saturated by water . A rockslide is a type of landslide that occurs when a sheet of rock moves downhill on a sliding surface. Rockslides are often triggered by earthquakes .

14. Waters Role in Mass Movement

15. Mass Movement

16. Rock moves because there nothing holding it back Genrally requies a pre-existing low- frictionsurface ….

17. Like a clay layer, once its wet….

18. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Slides When the mass of material in a landslide moves along a curved surface, a slump results. Material at the top of the slump moves downhill, and slightly inward, while the material at the bottom of the slump moves outward. Heavy rains Earthquakes

19. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Slides Landslides that occur in mountainous areas with thick accumulations of snow are called avalanches . Avalanches occur when snow that falls on an icy crust builds up, becomes heavy, slips off, and slides downslope.

20. Copyright © McGraw-Hill Education Mass Movements Types of Mass Movements Rockfalls On high cliffs, rocks that are loosened by physical weathering processes or by plant growth can break up and fall directly downward. Rockfalls commonly occur at high elevations, in steep road cuts, and on rocky shorelines.

21. Copyright © McGraw-Hill Education Mass Movements Mass Movements Affect People Human activities such as construction of buildings, roads, and other structures can make slopes unstable, contributing to the factors that cause mass movements.

22. Copyright © McGraw-Hill Education Mass Movements Mass Movements Affect People Reducing the risks The best way to reduce the number of disasters related to mass movements is to educate people about the problems of building on steep slopes.