soil - erosion

Question 1

how do soil and weathering products move across the land?

Answer 1

mass movment - by gravity - movement of soild rock

transport by water - runoff/ streams

transport by wind

Question 2

name 4 mass movements processes

Answer 2

flow

fall

slide

creep

Question 3

define FALL - ROCKFALL

Answer 3

single loosened rock tumbles downhill

form talus slopes - pile

Question 4

define FALL - EARTHFALL

Answer 4

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

beach cliffs or river cutbanks

Question 5

define SLIDES - ROCKSLIDES

Answer 5

large numbers of rocks cut loose at once and slide downhill

trapped air beneath rock cause large large speeds

Question 6

define SLIDES - ROTATIONAL SLUMP - LANDSLIDE

Answer 6

chunks of earth slide of hill in block

creates a cliff called scarp where ruptured occurred

Question 7

define SLIDE - DEBRIS SLIDE - LANDSLIDE

Answer 7

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

large hazard to life

Question 8

define SLIDE - MUDSLIDE

Answer 8

describes all kinds of slides and flows

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

eg Oso, 2014 deaths

Question 9

define FLOW- EARTHFLOW

Answer 9

friendliest flow

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

gradual

speeds of cm-m per hour

Question 10

define FLOW- DEBRIS FLOW

Answer 10

earth, water and rock mixed into fast moving liquid

speeds miles per hour

Clear creek, colorado

Question 11

define FLOW-MUDFLOW

Answer 11

fine material and water flowing

speeds like free flowing water

can be triggered by ice and snow melt - lahars

Question 12

name trigger mechanisms for slides and flows

Answer 12

heavy rain saturates soil

earthquakes cause liquefaction

removal of plant roots by deforestation or fire

graudal weathering causes spontaneous failure

Question 13

describe liquefaction

Answer 13

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

similar to quicksand

Question 14

define what creep is

Answer 14

material flowing downhill due to diffusional mechanisms

very slow

mechanism disrupts soil and gravity will pull more soil downslope

Question 15

name 4 creep mechanisms ?

Answer 15

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

Question 16

where does each mass movement mechanism operate?

Answer 16

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’

Question 17

how does water move sediment ?

Answer 17

Dissolved load- invisible

suspended load - small silt/clay

saltation - bouncing

rolling

bed load - bigger rocks and sand

Question 18

drainage overland flow

Answer 18

soil fully saturated so soil can’t infiltrate down

water puddles on surface which carries sediment

Question 19

sheetwash

Answer 19

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

Question 20

surface lowering

Answer 20

water dried up and exposes erosion degrdation

dry area

Question 21

drainage and flows - rills

Answer 21

water flow becomes channelized into small channels

sediment transported often to stream

rills can dry up - seasonal

Question 22

drainage and flow - gullies

Answer 22

rilles created into larger and deeper channels

lots of soil carried away

they can dry up and become eroded

Question 23

drainage and flow - streams

Answer 23

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

Question 24

where is the zone of deposition

Answer 24

at the mouth of river

lots of sediment here

Question 25

where is zone of transpotation

Answer 25

in the middle where the trunk stream is

Question 26

where is zone of production (erosion)

Answer 26

upand headwaters near tributaries

Question 27

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

Answer 27

Dam flat valley that glacier carved eg Yosemite

Question 28

effects of a dam

Answer 28

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

Question 29

effects in change in topography

Answer 29

may be due to tectonic uplift this creates waterfall knickpoint created becomes eroded and creates flat land again

Question 30

where does wind erosion occur most

Answer 30

arid environments where sediment is loose and less water for cohesion loose and dry material gets carried by wind

Question 31

what does wind do to sediment?

Answer 31

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

Question 32

how is aerial dispersion bad

Answer 32

not good for respiratory health

Question 33

difference between aerial dispersion and saltation

Answer 33

AD - finer material they create big dust storms up into sky saltation - lower lower not as big - larger sand particles

Question 34

how much of earth is degraded?

Answer 34

15% size of china and india 30 years ago so probz increased

Question 35

how much degradation does deforestation cause to land?

Answer 35

113ha

Question 36

how much degradation does overgrazing cause to land?

Answer 36

75ha

Question 37

how much degradation does poor cropping cause to land?

Answer 37

83ha

Question 38

name locations with high wind erosion?

Answer 38

open deserts or coasts

Question 39

locatiosn with high water erosion?

Answer 39

south africa grrece

Question 40

name 4 consqunces or erosion?

Answer 40

deforested land landslide blocks road gully erosion eats into cropland bridge destroyed by floods

Question 41

name 4 erosion and preventative methods?

Answer 41

reforest land gully erosion haulted by check dam points and trees planted steep land benched terraced river navigagtion improves fish catch

Question 42

describe dry, damp and wet sand?

Answer 42

dry sand bound together by friction damp sand - small amounts of water increase cohesion in grains wet sand - saturation reduces friction and sand flows