This chapter discusses two exogenic processes - weathering and mass wasting - that break down and transport rock materials at the Earth's surface. Weathering includes physical, chemical, and biological processes that break down rocks. Mass wasting describes the downslope movement of rock and soil under the force of gravity, ranging from slow processes like creep to rapid movements like landslides. The effectiveness of these processes varies based on climate, rock type, topography, and other environmental factors. Various examples are provided to illustrate different types of weathering and mass wasting.

1. Chapter 15: Weathering and Mass Wasting Physical Geography Ninth Edition Robert E. Gabler James. F. Petersen L. Michael Trapasso Dorothy Sack

2. Weathering and Mass Wasting

3. Weathering and Mass Wasting Exogenic processes: Breakdown rocks Erode rock materials Transport them Relocation by Gravity Geomorphic Agents Flowing water, wind Moving ice, waves

4. 15.1 Nature of Exogenic Processes Weathering: breakdown of rock materials at and near Earth’s surface Mass wasting

5. 15.1 Nature of Exogenic Processes Q: Can you identify evidence of the three phases shown in Figure 15.3?

6. 15.2 Weathering 3 Types of Weathering Physical weathering Mechanical weathering Chemical weathering Q: How might an animal cause physical weathering?

7. 15.2 Weathering Physical Weathering Person breaking a rock Unloading Thermal Expansion and Contraction Freeze-Thaw Salt Crystal growth Hydration

8. 15.2 Weathering Unloading Erosional stripping of overlying rocks and ultimate removal of overlying weight High elevation increases process

9. 15.2 Weathering Unloading Exfoliation Exfoliation sheet Exfoliation dome Stone Mountain, Georgia Half Dome (Yosemite)

10. 15.2 Weathering Thermal Expansion and Contraction Granular disintegration Differential thermal expansion and contraction of individual mineral grains in coarse crystalline rocks

11. 15.2 Weathering Freeze-Thaw Weathering Also called frost weathering (ice wedging) Water freezes it expands 9% Pipes bursting Angular blocks Effective in the upper-middle and lower-high latitudes

12. 15.2 Weathering Salt Crystal Growth Water with dissolved salt accumulates in these spaces and then evaporates, and growing salt crystals wedge rocks apart Hydration

13. 15.2 Weathering Chemical Weathering Most important catalysts and reactive agents: Water Oxygen Carbon dioxide 3 Types of chemical weathering: Oxidation Carbonation and Solution Hydrolysis

14. 15.2 Weathering Oxidation Iron and aluminum oxides Very common Carbonation and Solution Occurs when carbon dioxide in water reacts with rock material to produce bicarbonate ions

15. 15.3 Variability in Weathering Effectiveness of Weathering Climate Type of rock Nature and amount of fractures

16. 15.3 Variability in Weathering Climate Q: In which weathering region would we find a site that has an annual mean temperature of 5 o C (41 o F) and an annual rainfall of 100 cm (40 in)?

17. 15.3 Variability in Weathering Climate

18. 15.3 Variability in Weathering Rock Type Differential weathering and erosion Strong rock may be easily eroded in a different environment Structural Weakness Joints and fractures Exposed rock, collect salts, accumulation of water, and plants

19. 15.3 Variability in Weathering Structural Weakness Spheroidal weathering Q: With north at the top of this photo, what directions do the two most apparent joint sets trend?

20. 15.3 Variability in Weathering Topography Related to Differential Weathering and Erosion Grand Canyon

21. 15.3 Variability in Weathering Topography Related to Differential Weathering and Erosion Q: Can you see how the topography of the Ridge and Valley section influences human settlement patterns?

22. 15.4 Mass Wasting Mass Movement Downslope transport of material due to gravity Q: What other kinds of problems on roads are related to mass wasting?

23. 15.4 Mass Wasting Mass Movement Slope angle Creeping, falling, sliding, or flowing Gravity is the principal force Water is also a contributing factor

24. 15.4 Mass Wasting Classification of Mass Wasting Types of Earth Material Soil Debris Mud Categorized by speed Slow mass wasting Fast mass wasting

25. 15.4 Mass Wasting Slow mass wasting Creep Slow migration, but most persistent Heaving process Q: Are there places near where you live that show evidence of soil creep?

26. 15.4 Mass Wasting Q: What other constructed features might be changed by creep?

27. 15.4 Mass Wasting Slow mass wasting Solifluction Most common in high latitudes of high-elevation tundra Permafrost and active layer Summer thaw Tundra landscapes Q: How does solifluction differ from soil creep?

28. 15.4 Mass Wasting Fast Mass Wasting Four Major Types: Falls Avalanches Slides Flows Effects more dramatic than slow mass wasting

29. 15.4 Mass Wasting Falls Rockfalls Due to: Weathering weakens the bonds between clasts and cliff Large rock masses that fall from a cliff face or an overhanging ledge

30. 15.4 Mass Wasting Falls Talus slope Talus cone Angle of repose

31. 15.4 Mass Wasting Falls Happy Isles Rockfall in Yosemite Valley, CA Traveled at an estimated 250 km/hr (160 mph)

32. 15.4 Mass Wasting Avalanches Snow Rock Debris

33. 15.4 Mass Wasting Slides Water plays biggest role Rockslides Threaten lives and property Hebgen Lake rockslide Southwestern Montana (1959) Killed 28 people

34. 15.4 Mass Wasting Slides Debris slide Mudslide Slumps Landslide

35. 15.4 Mass Wasting Flows Earthflow Slump-earthflow Debris flows Mudflows Flow levees

36. 15.5 Weathering, Mass Wasting, and the Landscape Violent 1980 eruption of Mount St. Helens in Washington created lahars - mudflows

37. Physical Geography End of Chapter 15: Weathering and Mass Wasting