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Soil > soil - erosion > Flashcards

soil - erosion Flashcards

1
Q

how do soil and weathering products move across the land?

A

mass movment - by gravity - movement of soild rock

transport by water - runoff/ streams

transport by wind

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2
Q

name 4 mass movements processes

A

flow

fall

slide

creep

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3
Q

define FALL - ROCKFALL

A

single loosened rock tumbles downhill

form talus slopes - pile

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4
Q

define FALL - EARTHFALL

A

forms when steep slopes of soil and sediment are undercut - action of sea or river

beach cliffs or river cutbanks

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5
Q

define SLIDES - ROCKSLIDES

A

large numbers of rocks cut loose at once and slide downhill

trapped air beneath rock cause large large speeds

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6
Q

define SLIDES - ROTATIONAL SLUMP - LANDSLIDE

A

chunks of earth slide of hill in block

creates a cliff called scarp where ruptured occurred

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7
Q

define SLIDE - DEBRIS SLIDE - LANDSLIDE

A

a mass of water, rock and earth slides as a disintegrated plug

large hazard to life

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8
Q

define SLIDE - MUDSLIDE

A

describes all kinds of slides and flows

correctly means the sliding of soil and fine grained sediment and water

eg Oso, 2014 deaths

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9
Q

define FLOW- EARTHFLOW

A

friendliest flow

earth acts as liquid and slowly moves down hill - leaves scarp

gradual

speeds of cm-m per hour

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10
Q

define FLOW- DEBRIS FLOW

A

earth, water and rock mixed into fast moving liquid

speeds miles per hour

Clear creek, colorado

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11
Q

define FLOW-MUDFLOW

A

fine material and water flowing

speeds like free flowing water

can be triggered by ice and snow melt - lahars

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12
Q

name trigger mechanisms for slides and flows

A

heavy rain saturates soil

earthquakes cause liquefaction

removal of plant roots by deforestation or fire

graudal weathering causes spontaneous failure

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13
Q

describe liquefaction

A

earthquake causes soil to vibrate which weakens friction between sediment grains
less cohesion
sediment able to flow like liquid

similar to quicksand

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14
Q

define what creep is

A

material flowing downhill due to diffusional mechanisms

very slow

mechanism disrupts soil and gravity will pull more soil downslope

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15
Q

name 4 creep mechanisms ?

A

freeze thaw cycles (solifluction) - as soil freezes it expands and when it warms it collapses - creates pattern on ground

tree throw pulls soil out when it falls down hill

Rain splash- falls downhill due to gravity

animal burrowing or hoofs disperse soil

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16
Q

where does each mass movement mechanism operate?

A

rockfall and earthfall - very steep slope 60’

rotational slump, debris slide and mud slide - mid steep slope 60-20’

creep - any slope but only process to occur on <35’

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17
Q

how does water move sediment ?

A

Dissolved load- invisible

suspended load - small silt/clay

saltation - bouncing

rolling

bed load - bigger rocks and sand

18
Q

drainage overland flow

A

soil fully saturated so soil can’t infiltrate down

water puddles on surface which carries sediment

19
Q

sheetwash

A

water runs overland carrying sediment as heavy rain saturated soils and created overland flow

20
Q

surface lowering

A

water dried up and exposes erosion degrdation

dry area

21
Q

drainage and flows - rills

A

water flow becomes channelized into small channels

sediment transported often to stream

rills can dry up - seasonal

22
Q

drainage and flow - gullies

A

rilles created into larger and deeper channels

lots of soil carried away

they can dry up and become eroded

23
Q

drainage and flow - streams

A

runoff sustained by ground water

sediment moved by rills and gullies ends up here

sediment moved by massmovement will end up in stream

all year around transportation - doesn’t dry up

24
Q

where is the zone of deposition

A

at the mouth of river

lots of sediment here

25
Q

where is zone of transpotation

A

in the middle

where the trunk stream is

26
Q

where is zone of production (erosion)

A

upand headwaters

near tributaries

27
Q

what can a flat surface on river profile be due to?

A

Dam

flat valley that glacier carved eg Yosemite

28
Q

effects of a dam

A

distrupts flow of normal sediment

builds up behind dam so water carries no sediment

river will then be ‘hungry water’ which accumulates sediment from rest of river

29
Q

effects in change in topography

A

may be due to tectonic uplift this creates waterfall

knickpoint created

becomes eroded and creates flat land again

30
Q

where does wind erosion occur most

A

arid environments where sediment is loose and less water for cohesion

loose and dry material gets carried by wind

31
Q

what does wind do to sediment?

A

bigger boulders creep and roll along bottom

sand jumps via saltation

clay and silt suspended in air as smallest particles and can create dust storm - suspension or aerial dispersion

32
Q

how is aerial dispersion bad

A

not good for respiratory health

33
Q

difference between aerial dispersion and saltation

A

AD - finer material they create big dust storms up into sky

saltation - lower lower not as big - larger sand particles

34
Q

how much of earth is degraded?

A

15%
size of china and india

30 years ago so probz increased

35
Q

how much degradation does deforestation cause to land?

A

113ha

36
Q

how much degradation does overgrazing cause to land?

A

75ha

37
Q

how much degradation does poor cropping cause to land?

A

83ha

38
Q

name locations with high wind erosion?

A

open deserts or coasts

39
Q

locatiosn with high water erosion?

A

south africa

grrece

40
Q

name 4 consqunces or erosion?

A

deforested land

landslide blocks road

gully erosion eats into cropland

bridge destroyed by floods

41
Q

name 4 erosion and preventative methods?

A

reforest land

gully erosion haulted by check dam points and trees planted

steep land benched terraced

river navigagtion improves fish catch

42
Q

describe dry, damp and wet sand?

A

dry sand bound together by friction

damp sand - small amounts of water increase cohesion in grains

wet sand - saturation reduces friction and sand flows

Soil (3 decks)

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