mass movement and slope development

Question 1

what is mass movement

Answer 1

all downhill movement of regolith in response to gravity

Question 2

regolith?

Answer 2

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

Question 3

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

Answer 3

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

Question 4

solifluction

Answer 4

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

Question 5

Earthflows

Answer 5

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

Question 6

mudflows

Answer 6

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

Question 7

difference between slides and flows

Answer 7

slides do not suffer internal derangement and move en masse

Question 8

name 3 types of slides

Answer 8

planar landslide, rotational landslide, rockfall

Question 9

slope decline

Answer 9

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

Question 10

slope replacement

Answer 10

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

Question 11

parallel retreat

Answer 11

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

Question 12

how does rock structure effect slope development

Answer 12

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