3.3: slope processes

Question 1

aspect

Answer 1

• north facing slopes are more shaded:less susceptible for diurnal changes

Question 2

soil

Answer 2

• part of regolith
• type: how much water it can hold, how susceptible it is to mass movement

Question 3

vegetation

Answer 3

• can directly influence
• deforestation: risk of soil erosion, gullying
• roots support soils
• may influence landslips
• stem flow directs water, reduces raindrop impact
• CO2 released by decay
• roots release organic acids
• reduced physical weathering by protection os surface reducing thermal insulation

Question 4

geological structure

Answer 4

• different rock types: differential erosion: more likely to slip
• faults, strength, type, character influence vulnerability to weathering and degree of resistance to downfall movement

Question 5

climate

Answer 5

• climatic geomorphology
• slopes in humid areas tend to be more round (chem),arid more jagged (mechanical)
• intense rainfall: intense movements

Question 6

heave/creep

Answer 6

• def: lifting of soil particles perpendicularly out of the slope followed by a vertical drop to the surface
• smaller sections , prevalent
• over time: slow, small scale
• ripple: appearance of teracettes
• no obvious failure surface
• changes in moisture: change in volume as wetted/heated/frozen
• talus creep: movement of small fragments of rock (screep) down a slope

Question 7

slump/flow

Answer 7

• def: movement of often wet material on a wet slope with internal deformation and no noticeable failure surface
• smoother, more continuous movement, faster flow at surface
• thin channel : spreads out in a fan shape
• upper scar, stream incision (narrow flow path), debris deposited at toe in fan shape
• absorb water: pores saturated: increased weight: slip along lines of weaknesses: lose cohesion: unconsolidated material comes down together

Question 8

slides

Answer 8

• def: movement of material downhill along a slide (shear) plane en masse with no internal deformation
• movement along slip plane
• weakened rock, steep slope, undercutting
• gravity overcomes friction and cohesion
• retain shape until hit bottom
  -rotational slides leave steep head scar and a backwards dipping failure
• block planars also leave head scar and material disintegrates at base

Question 9

fall

Answer 9

• def: free movement of material often very fast from a very steep slope or cliff directly to the ground
• generally on slopes greater than 40 degrees
• especially on bare rock faces
• associated with weathering
• freeze thaw, seismic waves, gravitational stress,erosion along lines of weaknesses, human activity
• shorter fall : steeper scree slope, longer: fan shaped

Question 10

surface/sheet wash

Answer 10

• movement of water on a sloping surface as a uniform layer in unconcentrated form
• when the ground is saturated or frozen water will run over the surface taking material with it
• shallow sheets of water causes transportation of top layers of slope

Question 11

rills

Answer 11

• small networks of shallow channels created by thin, concentrated flows of water as a result of exceeded infiltration capacity
• erosive, gullies

Question 12

rainsplash erosion

Answer 12

• raindrop hits slope: dislodge loose soil : transport downhill
• more effective on steeper slopes, bare soil surface
• sufficient kinetic energy to dislodge