mass movement and slope development Flashcards

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1
Q

what is mass movement

A

all downhill movement of regolith in response to gravity

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2
Q

regolith?

A

looses uncemented mixture of soil and rock particles that cover the earths surface

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3
Q

what is soil creep? and explain 2 ways in which it occurs

A

soil creep is the slowest downhill movement with less than 1cm per year on slopes +- 5degrees

  • wet dry periods - heavy rainfall increases weight of soil causing expansion downhill. following dry period , soil dry out and contracts
  • Freeze Thaw - regolith freezes, ice crystals in soil increases volume , ground later thaws and lifted particles fall vertically down slope
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4
Q

solifluction

A

slightly faster movement at 5cm - 1m per year, occurs in periglacial conditions, in winter bedrock and regolith are frozen, summer causes surface layer to thaw but bedrock remains frozen, surface becomes saturated and moves downslope as an active layer

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5
Q

Earthflows

A

moves 1 - 15km per year on slopes 5 - 15 degrees, regolith saturated by water so moves downhill, may produce flow tracks which are tounge like shaped

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6
Q

mudflows

A

rapid movement at +- 1km/hr on steep slopes, following periods of intense rainfall , where both volume and weight are added to soil giving it higher water content than earthflow

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7
Q

difference between slides and flows

A

slides do not suffer internal derangement and move en masse

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8
Q

name 3 types of slides

A

planar landslide, rotational landslide, rockfall

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9
Q

slope decline

A

in humid climates, steepest slopes at the beginning of process, angle continues to decrease in time to give a convex upper slope and concave lower slope

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10
Q

slope replacement

A

in tectonic areas, maximum angle decreases as the gentler lower slopes erode back to replace steeper ones giving a concave central portion to the slope

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11
Q

parallel retreat

A

in semi arid landscapes, sea cliffs and wave cut platforms, maximum angle of slope remains constant as do all slope facets apart from the lowest one that increases in concavity

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12
Q

how does rock structure effect slope development

A

areas of bare rock are vulnerable to mechanical weathering and some chemical weathering processes
areas of alternating harder more resistant rock and softer less resistant rock is likely to experience movement

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