1. Chapter 8: Mass Movements, Wind, and Glaciers

2. The downslope movement of soil and weathered rock resulting from the force of gravity is called mass movement.
Climatic conditions determine the extent of mass movement.

3. All mass movements occur on slopes
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.

4. Factors that influence mass movements.
The material’s weight
The material’s resistance to sliding or flowing
Triggers that shake material loose, and
The presence of water.

5. 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.

6. One way to way to tell whether creep has occurred is to observe the positions of structures and objects.

7. Flows
Earth flows are moderately slow movements of soils, whereas mudflows are swiftly moving mixtures of mud and water.

8. Mudflows 8

9. Types of Mass Movements
Mudflows 9

10. Types of Mass Movements
Mudflows 10

11. Flows
Mudflows are common in sloped, semi-arid regions that experience intense, short-lived rainstorms.

12. Flows
Mudflows can be triggered by earthquakes or similar vibrations.
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.

13. Lahar - Flows 13

14. 14

15. Types of Mass Movements
Lahar - Flows
– pic 2 in New Zealand 15

16. 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.

17. 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.

18. Landslides 18

19. Types of Mass Movements
Slides
Landslides 19

20. Types of Mass Movements
Slides
rockslides 20

21. Types of Mass Movements
Slides
rockslides 21

22. 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.

23. slump 23

24. 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.

26. 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.

27. Wind Erosion and Transport
Limited precipitation leads to an increase in the amount of wind erosion because precipitation holds down sediments and allows plants to grow.

28. Wind transport and erosion primarily occur in areas with little vegetative cover, such as deserts, semiarid areas, seashores, and some lakeshores.

29. Deflation
The lowering of the land surface that results from the wind’s removal of surface particles is called deflation.

31. During the 1930s, portions of the Great Plains region experienced severe drought. Because large areas of natural vegetation had been removed, strong winds readily picked up the dry surface particles. The region became known as the Dust Bowl.

32. Another process of erosion, called abrasion, occurs when particles such as sand rub against the surface of rocks or other materials.

33. Because sand is often made of quartz, a hard mineral, wind abrasion can be an effective agent of erosion—windblown sand particles eventually wear away rocks.

34. Rocks shaped by windblown sediments are called ventifacts.

38. Wind Deposition
Dunes
In windblown environments, sand particles tend to accumulate where an object, such as a rock, landform, or piece of vegetation, blocks the forward movement of the particles. Over time, the pile of windblown sand develops into a dune.

39. The conditions under which a dune forms determine its shape and include the availability of sand, wind velocity, wind direction, and the amount of vegetation present.

40. Dune migration is caused when prevailing winds continue to move sand from the windward side of a dune to its leeward side, causing the dune to move slowly over time.

41. Thick, windblown silt deposits are known as loess.
Loess soils are some of the most fertile soils because they contain abundant minerals and nutrients.
Check audio. Should sound like luss.

42. This map shows the location of loess deposits in the continental United States.

43. Moving Masses of Ice A large mass of moving ice is called a glacier.
Glaciers form near Earth’s poles and in mountainous areas at high elevations. They cover about 10 percent of Earth’s surface.
Map of glaciers around the world. Glaciers cover roughly 10 percent of Earth's land area. A vast majority of that, 90 percent, overlies the continent of Antarctica . Read more: 

44. Glaciers that form in valleys in high, mountainous areas are called valley glaciers.
As valley glaciers flow downslope, they carve V-shaped stream valleys into U-shaped glacial valleys.

45. Valley Glaciers Bylot Island, Canada
 Bylot Island, Canada

46. Glaciers that cover broad, continent-sized areas are called continental glaciers.
These glaciers form in cold climates where snow accumulates over many years.

47. Both valley glaciers and continental glaciers move outward when snow gathers at the zone of accumulation, a location in which more snow falls than melts, evaporates, or sublimates.

48. Of all the erosional agents, glaciers are the most powerful because of their great size and weight.

49. When a valley glacier moves, it breaks off pieces of rock through a process called plucking.
When glaciers with embedded rocks move over bedrock, they act like grains on a piece of sandpaper, grinding parallel scratches into the bedrock.

50. At the high elevations where snow accumulates, valley glaciers scoop out deep, bowl-shaped depressions, called cirques.

54. When there are glaciers on three or more sides of a mountaintop, the carving action creates a steep, pyramid-shaped peak, called a horn.

57. Hanging valleys are formed by valley glaciers when higher tributary glaciers converge with the lower primary glaciers and later retreat. A valley is left hanging high above the primary valley floor.

60. Glacial till is the unsorted rock, gravel, sand, and clay that glaciers carry embedded in their ice and on their tops, sides, and front edges.
Glaciers deposit unsorted ridges of till called moraines when the glacier retreats.

63. When the farthest ends of a glacier melt, meltwater floods the valley below. Outwash is the gravel, sand, and fine silt sediment that is deposited by meltwater carried away from the glacier.

64. The area at the leading edge of a glacier where meltwater flows and deposits outwash is called an outwash plain.

66. Continental glaciers that move over older moraines form the material into elongated landforms called drumlins.

69. Streams flowing under melting glaciers leave long, winding ridges of layered sediments called eskers.
A kame is a mound of layered sediment that forms when till gets washed into depressions or openings in the melting ice.

72. Continental glaciers carve out vast regions of landscape, leaving behind distinctive features such as kames, eskers, drumlins, and moraines.

73. Kettles, or kettle lakes, form when water from runoff or precipitation fills a hole that formed when a large block of ice broke off a continental glacier and melted.

76. With valley glaciers, cirques can also fill with water and become cirque lakes.
When a terminal moraine blocks off a valley, the valley fills with water to form a moraine-dammed lake.