# BYU GEO 110 Ch 7

 What is mass wasting?
 downslope movement of earth’s materials
 the term landslides sometimes includes
 debris flow, rock falls, and avalanches
 The most common landform on the erath
 Slopes.
 Where are free face slopes more common?
 On strong rocks or in arid environments.
 Describe a free face slope.
 A high cliff of hard rock that forms a straight, nearly vertical slope segment.
 What is talus?
 Rock fall that accumulates at the base of a cliff or slope
 Types of landslides
 FallingSlidingSlumpingFlowage/flowCreep
 Falling landslide
 free fall of material
 Sliding landslide
 downslope movement of a coherent block of earthmaterial along a planar slip plane
 Slumping landslide
 Sliding along a curved slip plane producing slump blocks.
 Flowage or flow landslide
 Downslope movement of unconsolidated material in which particles move about and mix within the mass
 Creep landslides
 Very slow flowage. Progressively tilts telephone poles, fences and tree trunks. Trees grow faster than creep moves, so tress are crooked.
 Four variables in downslope movement
 1- The mechanism of the movement (slide, fall, flow or complex movement) 2- Type of earth material (solid rock, soft consolidated sediment or loose material) 3- Amount of water present 4- Rate of movement
 Forces that influence slope stability
 Driving forcesResisting forcesShear strength
 Driving forces on slopes
 Move earth materials down a slope
 Resisting forces on slopes
 Oppose the downward driving forces
 Shear strength on slopes
 The most common resisting force. Resists by sliding or flowing along potential slip lines
 Slope stability is evaluated by…
 calculating the Safety Factor.
 How to calculate safety factor
 The ratio of the resisting forces to the driving forces. Greater than 1 is stable, the resisting forces exceed the driving forces. Less than 1 – slope failure can be expected b/c driving forces exceed the resisting forces.
 The shape of the slip surface in slides is strongly conrolled by the type of __________________.
 earth material
 Slides have two basic patterns of movement.
 Rotational, with curved slip surfacesandTranslational, planar slip surfaces
 Slumps are most common in
 unconsolidated earth material and in mudstone, shale and other weak rocks.
 Movement in translational slides
 moves along inclined slip planes within and parallel to a slope.
 Debris flow
 thick mixtures of mud, debris, and water.
 Angle of repose
 The angle at which snow, or any loose material, is stable. Generally, stable at less than 25 degrees.
 Two types of snow avalanches
 Loose-snow avalanches – starts at a point and widens as it moves downslope Slab avalanches – start has cohesive blocks of snow and ice that move downslope.
 Chutes
 Tracks produced by previous avalanches that future avalanches will usually follow
 Three factors that will increase world-wide landslide activity.
 Development in landslide prone areasTreecutting in landslide prone areasChanging global climate patterns will produce regional increases in precipitation
 Direct effects of landslides