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CHAPTER 5.3 MASS MOVEMENTS

CHAPTER 5.3 MASS MOVEMENTS. “The transfer of rock and soil downslope due to gravity.”. Some types of mass movement are so slow you can’t see them moving. Year: 2009. Year: 2020. Year: 2050. Year: 2070. CHATER 5.3 MASS MOVEMENTS.

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CHAPTER 5.3 MASS MOVEMENTS

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  1. CHAPTER 5.3 MASS MOVEMENTS “The transfer of rock and soil downslope due to gravity.” Some types of mass movement are so slow you can’t see them moving. Year: 2009 Year: 2020 Year: 2050 Year: 2070

  2. CHATER 5.3 MASS MOVEMENTS “The transfer of rock and soil downslope due to gravity.” Some types of mass movement are very sudden.

  3. Triggers of Mass Movement When pores in sediment become filled with water. Saturation by Water Saturation provides a slippery medium upon which the soil particles can slide. Saturation adds weight to the soil causing it to break loose and slide downslope.

  4. Triggers of Mass Movement Slopes that are steeper than about 40 degrees. Oversteepened Slopes Soils can remain stable on slopes up to about 25-40 degrees. Can be caused by wave action or human construction processes. 40 degree slope

  5. Triggers of Mass Movement Cutting or replacement of plants that secure the soil. Removal of Vegetation Plant roots bind soil and regolith together. Removal of plants removes the “rope” that holds the soil in place.

  6. Triggers of Mass Movement Earthquakes Rapid movement of tectonic plates. Triggers abrupt and often violent mass movement. Can dislodge large amounts of soil at once.

  7. Types of Mass Movements Geologists classify mass movements based on… … the kind of material that moves (rocks, mud, snow) … how the material moves (slides, flows, slumps) … the speed of the movement (creep)

  8. Types of Mass Movements Rockfalls … • occur when rocks or rock fragments fall freely through the air. Rockslides … • occur when a block of material moves suddenly (fast) along a flat, inclined surface.

  9. Types of Mass Movements Slumps … • occur when material moves downward along a curved surface. • leave a crescent shaped cliff just above the slump.

  10. Types of Mass Movements Flows … • occur when material containing a large amount of water move downslope as a thick fluid • “mudflows” move quickly • “earthflows” move slowly

  11. Types of Mass Movements Creeps … • moves only a few millimeters or centimeters per year. • affected by freezing and thawing • cannot be observed directly as it happens (too slow) 1 mm A B

  12. Types of Mass Movements Creeps … HSW: Geography Basics: Five Ways Lands Change

  13. Sideling Hill

  14. Assignment: Read pgs 148-149. Answer the questions under “ASSESSMENT” on pg 149. DO NOT do Question 5(c).

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