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Physical Geography > Slope Processes and Development > Flashcards

Slope Processes and Development Flashcards

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1
Q

describe a slope in an arid area?

A

jagged or straight due to mechanical weathering or shestwash

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2
Q

describe a slope in a humid area?

A

rounder
due to ecumenical weathering
soil creep
and fluvial transport

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3
Q

describe a slope in the tropics?

A

humid weather means domination of chemical weathering
due to hot wet conditions and avalibility of organic acids

deep flat produced favouring low slope angles

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4
Q

what is revoking?

A

the superficial and unconsolidated material at earths surface

including soil scree weathered bedrock and deposited material

prone to downslope movement (due to unconsolidated nature)

clay rich are particularly unstable due to ability to hold water

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5
Q

how can soil structure and texture influence slope development?

A

clay soils hold more water

dee clay on a slope where vegetation has been removed will offer very little resistance to mass movement

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6
Q

how can vegetation affect slope development?

A

can decrease surface runoff through storage and interception

deforested slopes are exposed to intense erosion and filleting

vegetarion can increase chance of major landslides

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7
Q

dry mass movement

A

rock fall

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8
Q

fluid mass movement

A

mud flow

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9
Q

very slow mass movement

A

soil creep

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10
Q

fast mass movement

A

avalanche

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11
Q

what is mass movement

A

large scale movements on the earths surface not accompanied by a moving agent such as a river or ocean wave

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12
Q

what are the most important factors in determining mass movement

A

gravity
slope angle
pore pressure

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13
Q

what factors influence slope development

A 
rock type 
climate
regality
soil
aspect
vegetation
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14
Q

what two factors cause slope failure

A

reduction in internal resistance SHEAR STRENGTH of slope

Increase in SHEAR STRESS of the slope (the forces attemption to pull the material downslope)

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15
Q

what is the effect of gravity on mass movement

A

moves material downslope

sticks partciles to slope

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16
Q

where do slip planes occur

A 
at the junction of two layers
at fault lines
at a joint
along a bedding plane
when shear stress is rested than shear strength
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17
Q

Heave/creep

A

slow
small scale
occurs mostly in winter

indidcual soil particles are pushed to surface by wetting heating or freezing of water
particles move at right angles to the surface as it is the path of least resistance
fall under the influence of gravity when the particles have dried, cooled or water has thawed

net movement downslope

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18
Q

Talus creep

A

slow movement of fragments on scree slope

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19
Q

what does the majority of soil creep movement come from

A

75% induced by moisture and so volume change

20
Q

how are individual soil particles heaved to surface?

A

wetting
heating
freezing

21
Q

what feature can heave form

A

terracettes

22
Q

what are the initial causes of falls

A

weathering e.g. freeze thaw or disintegration

or erosion prising open lines of weakness

23
Q

how can the length of rock fall influence scree

A

long - rounded scree

short - relatively straight

24
Q

what do falls cause on rock faces

A

retreat

25
Q

where do falls occur

A

steep slopes
greater than 40 degrees
especially bare rock faces
where joints are exposed

26
Q

when do slides occur

A

when an entire mass of material moves along a slip plane

27
Q

different types of slides

A

rotational slides - producing series of massive steps or terraced

rockslides or landslides or material rock or regith

28
Q

when do slides commonly occur

A

weak rocks
steep slopes
active undercutting

change in the water content of slipe
or very cold conditions

29
Q

what type of rock is vulnerable to slip planes and why

A

clay because it has little shear st engraved

slip plane is concave curve and the slide occurs the mass will be rotated backwards

30
Q

when do loose rocks stone and soil move downslope

A

when downslope force exceeds resistance produced by friction and cohesion

31
Q

when does a landslide occur

A

when material moves downslope due to shear failure at the boundary of the moving mass

32
Q

what are landslides sensitive to and why

A

water content
reduced the strength of the material by increasing internal pressure
this pushes particles apart
weakening the links between them
water adds weight to mass increasing downslope force

33
Q

what type of rocks do slumps occur on

A

weaker rocks

especially clay

34
Q

how do slumps and flows differ from landslide

A

high water content

smaller particles

35
Q

how does a flow differ from a slump

A

flows are

more continuous
less jerky
more likely to contort mass
material involved is predominately fine particles e.g. deeply weathered clay

36
Q

when does a slump occur

A

when clay absorbs water
becomes saturated
exceeds liquid limit
flows along a slip plane

frequently the base of a cliff has been undercut and weakened by erosion thus reducing its strength

37
Q

example of a slump

A

Average
21 October 1966
144 killed
116 of which were school children

38
Q

fact about the material in a slump

A

33% is fine grained

39
Q

how does the speed of flows vary

A

mudlflows are much faster than earth flows
and more fluid

higher water content enables material to flow across gentler angles

40
Q

what are avalanches

A

rapid movements of snow ice rock or earth down a slope

snow and ice may pick up rocks and or earth

41
Q

in mountainous steep areas how does a rock fall differ from a rock avalanche

A

rock avalanche is large scale movement to material

rock fall could be individual rocks

42
Q

where are avalanches common

A

steep slopes over 22 degrees especially on north facing slopes where the lack of sun inhibits stabilisation of snow

mountainous areas

43
Q

dry acalanche

A

newly fallen snow falls off older snow

winter

44
Q

wet avalanche

A

in spring partially melted snow moves often triggered by skiing

45
Q

what is a debris avalanche

A

rapid mass movement of sediment often associated with saturated ground conditions

Physical Geography (6 decks)

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