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GEOLOGY > UNIT 9 Mass movement > Flashcards

UNIT 9 Mass movement Flashcards

1
Q

what are the types of mass movement

A

Solufluction and creep
Slumping
Lahars and mudflows
debris flows
rockfalls and rockslides

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2
Q

what is a mass movement

A

the downslope movement of rock, regolith, snow or ice driven by gravity

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3
Q

You can distinguish Mass movements by

A

Material
velocity
Character
Environment

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4
Q

What are the types of material in a mass movement

A

snow, rock, mud, ice

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5
Q

What are the characters of sediment in mass movement

A

coherent or chaotic

wet or dry

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6
Q

what are the mass movement environments

A

subaeriel submarine

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7
Q

What is creep

A

slow downhill movement of regolith caused by seasonal expansion and contraction

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8
Q

What is evidence of creep

A

Tilted telephone poles, sagging foundation, curving tree trunks

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9
Q

WHat is solufluction

A

Tundra Creep where melted permafrost slowly flows over deeper frozen soil

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10
Q

What are rock glaciers

A

rock glaciers are mixtures of rock fragments imbedded in ice

think breccia or conglomerate cemented in ice

because ice is relatively week it can flow slow down steep slopes

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11
Q

what is slumping

A

mass movement by sliding of regolith in coherent blocks

have a head scarp (exposed failure)
and a bulging toe (material pile up)

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12
Q

What is a mud flow

A

Mostly mud mass movement, depends on water content and slope angle

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13
Q

what is a debris flow

A

mud flow mixed with pebbles and cobbles

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14
Q

what are lahars

A

same process as a mudflow or debris flow but with volcanic ash instead of weathered regolith

super hot and scary and stuff

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15
Q

what is a rock/debris slide

A

non vertical,
rock can move at 300km/h
rock slide if rock
debris slide if regolith

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16
Q

what is an avalanche

A

the best beaver tail flavour

a turbulent cloud of debris and air
snow or other debris like rock or marine sediment

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17
Q

wet snow avalanche speed

A

30km/h

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18
Q

dry snow avalanche speed

A

20km/h

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19
Q

avalanches flow through….

A

channels down mountains or underwater

20
Q

What is a rock / debris fall

A

vertical Freefall of mass
falls rapidly
caused by road cuts

21
Q

what happens in submarine slumps and debris flow

A

sediment breaks loose and flows down a canyon

the turbidity current slows and deposits sediment in a submarine fan

22
Q

in a turbidity current..

A

sediment and water flow chaotically downslope

23
Q

physics of mass movement

A

moves when the downslope force is greater than the resisting force

which is caused by many factors like chem bonds electrostatic attraction friction and surface tension

24
Q

sand angle of repose

A

35 deg

25
Q

coarse sand angle of repose

A

40 deg

26
Q

angular pebbles angle of repose

A

45 deg

27
Q

what are weak surfaces

A

saturated sand or clay layers

joints parallel to surface

weak sedimentary bedding

metamorphic foliation

28
Q

what triggers mass movement

A

shocks

vibrations

liquefaction

changes in slope loads, steepness and support

changes in slope strength

29
Q

what causes shocks and vibrations

A

earthquakes
storms
trucks
blasting

30
Q

what is liquefaction

A

when wet sediment shakes, grains can behave like fluid, solid sediment turns into a slurry

31
Q

what can cause changes in slope loads

A

addition of weight above a slope
water infiltration
construction

32
Q

what can cause changes in steepness (MM)

A

rivers and road cuts

33
Q

what can cause changes in support (MM)

A

undercutting may remove support and create a steeper slope

34
Q

what can cause changes in slope strength

A

weathering
vegetation
water content

35
Q

what happened in the vajont dam

A

water table rose above the dam and overflowed causing massive destruction

36
Q

what magnitude was the 1929 NFL earthquake

A

7.2

37
Q

Where do slope failures occur

A

HIGH RELIEF AREAS
revers glaciers waves

HIGH RAIN AREAS
weathering heavy soil

TECHTONIC AREAS

38
Q

how do you identify mass movement

A

look for indications of past mass movement such as head scarps, overtight power lined, dead or tilted trees

39
Q

how does vegetation prevent mass movement

A

the roots stabilize the potential failure plane

40
Q

what is regrading

A

cutting terrace steps to remove load and catch debris

41
Q

What is drainage in mass movement prevention

A

lowering the water table below a potential failure plane dries the plane and makes it stronger

42
Q

how can you reduce undercutting

A

divert a stream further from a cliff
place riprap to absorb wave energy

43
Q

What are some ways engineered structures to help prevent the effects of mass movement

A

Retaining walls
Jock bolts
avalanche sheds

44
Q

When do you use controlled blasting

A

if a slide is inevitable,Avalanches usually

45
Q

what is nessecary to set a mass movement in motion

A

weathering, relief, a triggering event

GEOLOGY (12 decks)

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