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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
Component of gravitational force parallel to slope(shear force) ___________ with slope steepness
increases
26
If shear ______ exceeds sheer _______, slopes can fail
force Strength
27
Shear strength is a _________ force to moving downslope Shear force is a _________ force to moving downslope
frictional gravitational So frictional reduces the movement downslope, and gravitational wants to move down the slope
28
What are the 4 natural processes that cause mass wasting
earthquakes, rainfall, chemical/mineralogical changes, frost wedging/thawing
29
What are 4 human activities that cause mass wasting
adding weight, slope steepening, increasing moisture, and removing vegetation
30
What are the 3 characteristics used to classify mass movements
type of material that fails Rate of movement mechanism of failure
31
Are all mass movements landslides
no
32
Define a creep
A gradual downslope movement of soil or regolith
33
When and where do terracettes form
they form during a soil creep and are typically combined with a freeze-thaw cycle or cycles of soil saturation and drying
34
Define solifluction
Freeze-thaw activity generated mass movement thawed water saturated soil flows over frozen layer underneath
35
What does solifluction typically form
lobes and sheets on slopes
36
Define a curved rupture surface shape and where we would see it
rotational slope failure slump
37
define a flat rupture surface and where we would see it
translational slope failure rock slide
38
What kind of mass movement forms stair step pattern of displaced blocks and hummocky ridges near the toe
slumping
39
Why do slump occurs
erosion or undercutting at base of slope
40
define slumping
concave and cliff-like scarp ( steep slope) block moves coherently along the failure plane
41
Rock slides occurs when
frost wedging has loosened jointed bedrock layers which move downhill as a unit
42
rock fall occurs when
ice wedging often breaks rocks along joints, preparing them to loosen and fall away
43
Which mass wasting event is it when individual blocks free-fall down a slope
rock fall
44
What is the type of material, rate of movement and mechanism of a rock fall?
rock fast fall
45
What are the characteristics and processes of a mud flow
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
The 2014 Oso landslide was what kind of mass movement
mud flow
47
4 reasons why some areas are particularly prone to mass wasting
Steep mountainous terrains, high precipitation, abundance of unconsolidated glacial sediments, geographic position
48
What is the type of material, type of motion and rate of motion for rock fall
rock fragments vertical or near vertical fall very fast
49
What is the type of material, type of motion and rate of motion for rock slide
a large rock body translational sliding typically very slow, sometimes can be fast
50
What is the type of material, type of motion and rate of motion for creep or solifluction
soil or soil mixed with ice flow very slow
51
What is the type of material, type of motion and rate of motion for slump
thick deposits of unconsolidated sediment rotational sliding slow
52
What is the type of material, type of motion and rate of motion for mudflow
loose sediments with a significant component of silt and clay flow moderate to fast
53
What is the type of material, type of motion and rate of motion for debris flow
sand, gravel, and larger fragments flow fast
54
What is the largest recorded slide in Canadian history
The Hope slide
55
What is the deadliest slide in Canadian history
The Frank Slide
56
Why did the Frank slide happen
folded sedimentary rock with vertical joints and bedding planes weathering, erosion decreased rock strength
57
What type of slide was the saint-Jude slide
clay - quickclay It took the house down because the surface underneath became like quicksand
58
How does quick clay come to be
Groundwater flowing though the clay removes ions left behind by the seawater, this makes the clay weaker over time
59
leda (quick) clay slides, describe why liquefaction and slides occur
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
What are ways we can prevent mass wasting
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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