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Geology 102 > Mass wasting > Flashcards

Mass wasting Flashcards

1
Q

Define weathering

A

Chemical and physical processes that produce soils, clays, sediments, and dissolved substances

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2
Q

Define erosion

A

removal and transport of particles produced by weathering from their source by wind, water, ice

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3
Q

Define mass wasting

A

movement of earth materials down a slope due to gravitational force

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4
Q

Mass wasting is influenced by three primary factors

A

material characteristics
water content
slope steepness

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5
Q

Define what material characteristics, water content, and slope steepness describe

A

Material characteristics: slopes may be composed of unconsolidated (regolith) or unconsolidated materials
Water content: affected by precipitation and material porosity
Slope steepness: influences how materials move under various climates

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6
Q

Out of the 3 factors of mass wasting, which ones are more strongly influenced by human activity

A

slope steepness and water content

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7
Q

Are consolidated or unconsolidated materials stronger

A

consolidated

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8
Q

Define angle of repose

A

Maximum angle of unconsolidated materials

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9
Q

The angle of repose is greater for ________ and less _______ materials

A

courser and less rounded materials

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10
Q

Does fine sand or angular pebbles assume a shallower angle of repose

A

fine sand

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11
Q

particles dropped in a pile create an angle of repose based on their ______ and ______

A

size and angularity

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12
Q

unconsolidated sand and silt have what for a maximum angle of repose

A

35 degrees
steeper slopes will collapse

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13
Q

unconsolidated materials include what kind of materials

A

sand, silt, clay, soil, and rock fragments
They can moderate to steep slopes

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14
Q

What are types of consolidated materials

A

rock, lithified sediments, vegetated soils, and cohesive particles
they often form more stable slopes

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15
Q

Mass movement of consolidated materials are usually linked to increasing _______ _______

A

water content

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16
Q

Does water content affect the stability of consolidated and unconsolidated material

A

sure does

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17
Q

Why do saturated materials lose strength

A

water reduces frictional forces between particles

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18
Q

What happens if water content increases enough to allow materials to flow as a fluid

A

liquefaction

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19
Q

List these from most cohesive to least: dry sand, damp sand, water-saturated sand

A

Damp sand, dry sand, water-saturated sand

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20
Q

Describe the water content and unconsolidated sediment cohesion of damp sand

A

dampness binds sand particles so that they resist movement

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21
Q

Describe the water content and unconsolidated sediment cohesion of dry sand

A

dry particles are bound only by their size and friction with one another

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22
Q

Describe the water content and unconsolidated sediment cohesion of water-saturated sand

A

saturated particles are separated by water, which keeps the grains apart and also acts as a lubricant, allowing them to flow

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23
Q

Surface tension: Water molecules in a liquids interior are _________ in all directions. Surface molecules have a net _______ attraction that results in surface tension allowing objects to _______.

A

attracted
inward
float

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24
Q

Stability of slopes depend on

A

physical characteristics of soil, rock and other slope materials, including water.

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25
Q

Component of gravitational force parallel to slope(shear force) ___________ with slope steepness

A

increases

26
Q

If shear ______ exceeds sheer _______, slopes can fail

A

force
Strength

27
Q

Shear strength is a _________ force to moving downslope
Shear force is a _________ force to moving downslope

A

frictional
gravitational

So frictional reduces the movement downslope, and gravitational wants to move down the slope

28
Q

What are the 4 natural processes that cause mass wasting

A

earthquakes, rainfall, chemical/mineralogical changes, frost wedging/thawing

29
Q

What are 4 human activities that cause mass wasting

A

adding weight, slope steepening, increasing moisture, and removing vegetation

30
Q

What are the 3 characteristics used to classify mass movements

A

type of material that fails
Rate of movement
mechanism of failure

31
Q

Are all mass movements landslides

A

no

32
Q

Define a creep

A

A gradual downslope movement of soil or regolith

33
Q

When and where do terracettes form

A

they form during a soil creep and are typically combined with a freeze-thaw cycle or cycles of soil saturation and drying

34
Q

Define solifluction

A

Freeze-thaw activity generated mass movement
thawed water saturated soil flows over frozen layer underneath

35
Q

What does solifluction typically form

A

lobes and sheets on slopes

36
Q

Define a curved rupture surface shape and where we would see it

A

rotational slope failure
slump

37
Q

define a flat rupture surface and where we would see it

A

translational slope failure
rock slide

38
Q

What kind of mass movement forms stair step pattern of displaced blocks and hummocky ridges near the toe

A

slumping

39
Q

Why do slump occurs

A

erosion or undercutting at base of slope

40
Q

define slumping

A

concave and cliff-like scarp ( steep slope)
block moves coherently along the failure plane

41
Q

Rock slides occurs when

A

frost wedging has loosened jointed bedrock layers which move downhill as a unit

42
Q

rock fall occurs when

A

ice wedging often breaks rocks along joints, preparing them to loosen and fall away

43
Q

Which mass wasting event is it when individual blocks free-fall down a slope

A

rock fall

44
Q

What is the type of material, rate of movement and mechanism of a rock fall?

A

rock
fast
fall

45
Q

What are the characteristics and processes of a mud flow

A

characteristics: water permeable soil and water impermeable rocks
Process: Rain has soaked fine grained permeable rocks which loosen quickly and flow downhill over impermeable rocks at moderate speeds

46
Q

The 2014 Oso landslide was what kind of mass movement

A

mud flow

47
Q

4 reasons why some areas are particularly prone to mass wasting

A

Steep mountainous terrains, high precipitation, abundance of unconsolidated glacial sediments,
geographic position

48
Q

What is the type of material, type of motion and rate of motion for rock fall

A

rock fragments
vertical or near vertical fall
very fast

49
Q

What is the type of material, type of motion and rate of motion for rock slide

A

a large rock body
translational sliding
typically very slow, sometimes can be fast

50
Q

What is the type of material, type of motion and rate of motion for creep or solifluction

A

soil or soil mixed with ice
flow
very slow

51
Q

What is the type of material, type of motion and rate of motion for slump

A

thick deposits of unconsolidated sediment
rotational sliding
slow

52
Q

What is the type of material, type of motion and rate of motion for mudflow

A

loose sediments with a significant component of silt and clay
flow
moderate to fast

53
Q

What is the type of material, type of motion and rate of motion for debris flow

A

sand, gravel, and larger fragments
flow
fast

54
Q

What is the largest recorded slide in Canadian history

A

The Hope slide

55
Q

What is the deadliest slide in Canadian history

A

The Frank Slide

56
Q

Why did the Frank slide happen

A

folded sedimentary rock with vertical joints and bedding planes
weathering, erosion decreased rock strength

57
Q

What type of slide was the saint-Jude slide

A

clay - quickclay
It took the house down because the surface underneath became like quicksand

58
Q

How does quick clay come to be

A

Groundwater flowing though the clay removes ions left behind by the seawater, this makes the clay weaker over time

59
Q

leda (quick) clay slides, describe why liquefaction and slides occur

A

glaciomarine clays: deposited in sea
water. The clay deposits contain up
to 80% water, held together by
surface tension.
* Clays lose shear strength due to
long-term fresh water flushing that
removes ions in the clay
liquefaction and slides can occur due to high rainfall or seismic events

60
Q

What are ways we can prevent mass wasting

A

vegetation (stabilizes slope and improves slope stability of slope for water run-off)
Regrading slopes (fill and cut)
Preventing undercutting (placing riprap to prevent erosion at base of slope)
Decrease weight on slope
decrease water infiltration (directing runoff using drainage)
rock bolts, netting, water drainage
frequent monitoring and inspection

Geology 102 (11 decks)

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