Mass Wasting - TRIGERRING MECHANISM

Question 1

it is the most significant factor that could trigger mass wasting

Answer 1

degree of slope

Question 2

t or f: as the slope increases, the gravitational component acting parallel to the slope, also increases

Answer 2

T

Question 3

when ______ becomes greater than the ______, downslope movement can occur

Answer 3

gravitational force ; frictional forces

Question 4

the following factors may trigger mass wasting:

Answer 4

Nature of slope material;
oversteepened slopes
vegetation and climate;
earthquake and volcanic activities

Question 5

t or f: strong and homogenous rocks are able to form stable cliffs

Answer 5

T

Question 6

what type of rock is the cliff on Yosemite Valley, California?

Answer 6

granite rock

Question 7

how long was the rock in Yosemite Valley, California? how did it become so stable?

Answer 7

2,000 foot

interlocking mineral grains and resistance to weathering

Question 8

t or f: frictional forces in loose sediments are higher than in solid rocks

Answer 8

F (lower)

Question 9

is the steepest angle at which a sloping surface of unconsolidated sediment is stable

Answer 9

angle of repose

Question 10

angle of repose is typically

Answer 10

<35 degrees

Question 11

t or f: large angular fragments generate greater frictional forces compared to small, well-rounded fragments

Answer 11

T

Question 12

can occur along bedding planes, foliation planes, fractures, and fault surfaces that are inclined in the same direction as the slope

Answer 12

slippage

Question 13

where does slippage usually occur?

Answer 13

foliation plane, bedding plane, fracture and fault surfaces

Question 14

t or f: slippage are inclined in the opposite direction as the slope

Answer 14

F (same direction)

Question 15

in the Grand Canyon, steep cliffs develop in resistant ______ and ______, whereas broad, gentle slopes form in much weaker ______

Answer 15

limestones and sandstones;

shales

Question 16

what is daylight structure?

Answer 16

areas of high susceptibility to mass wasting because it is facing plane of weaknesses inclined to the slope

Question 17

undercutting of stream banks results in _____ and _____

Answer 17

cutbanks and overhang

Question 18

what causes cutbanks?

Answer 18

natural migration of stream channel

Question 19

t or f: river valleys become wider over time due to undercutting of stream banks

Answer 19

T

Question 20

example of oversteepened slopes caused by human actvity

Answer 20

excavation of materials from hillsides in order to create a leveled surface for construction of roads, buildings, and parking lots

Question 21

t or f: only natural processes can destabilize a slope by increasing its steepness

Answer 21

F (natural and unnatural)

Question 22

long-term average weather

Answer 22

climate

Question 23

vegetation that blankets slopes influences the fraction of _____ or ____ that ______ into the subsurface

Answer 23

rain or snow;

infiltrates

Question 24

how does fairly dense vegetation stabilize slopes?

Answer 24

plant roots help in binding particles and loose sediments together

Question 25

t or f: during unusually large rainstorms or rapid snowmelts, dense vegetation will increase infiltration since it reduces the ability of surface water to move downslope, therefore destabilizing the slope bc of excessive infiltration

Answer 25

T

Question 26

________ adds significant weight to a slope and reduces friction through higher pore pressures

Answer 26

excessive infiltration

Question 27

excessive infiltration reduces friction in slope because of ______

Answer 27

increased pore pressure

Question 28

vegetation vs geology: which is more influential factor of mass wasting?

Answer 28

geology

Question 29

how does seismic waves destabilize slopes?

Answer 29

ground vibrations reduces the frictional forces within the slope material, as well as causing them to liquefy

Question 30

seismic waves also cause materials to ____, which can immediately destabilize a slope and trigger a mass wasting event

Answer 30

liquefy

Question 31

infiltrated water within slope material increases _______, which then reduces _______ between the solids

Answer 31

pore pressure ; frictional forces

Question 32

general potential causes of mass movements

Answer 32

geological morphological physical anthropogenic

Question 33

give at least 3 geological causes of mass movements

Answer 33

weak material sensitive material weathered material sheared material jointed or fissured material

Question 34

give at least 3 morphological causes of mass movements

Answer 34

tectonic or volcanic uplift glacial rebound erosion of slope toe erosion of lateral margins vegetation removal

Question 35

give at least 3 physical causes of mass movements

Answer 35

intense rainfall rapid snow melt earthquake volcanic eruption

Question 36

give at least 3 human causes of mass movements

Answer 36

deforestation irrigation mining drawdown of reservoirs excavation of the slope

Question 37

give at least 3 human causes of mass movements

Answer 37

deforestation irrigation mining drawdown of reservoirs excavation of the slope

Question 38

manifestations to look at when identifying landslides

Answer 38

vegetation cover; presence of cracks or scars; disrupted drainage pattern; excessive soil moisture/abrupt soil moisture changes; terrain form; tilting of trees/posts

Question 39

morphological diagnostics

Answer 39

concave-convex; step-like morphology; semicircular niche; back tilting of slope faces; hummocky relief; formation of cracks; steepening of slopes; vegetation clearances on steep scarps; irregular linear clearances along the slope

Question 40

the sequence of a concave and convex part of the slope is associated with :

Answer 40

landslide niches and associated deposit

Question 41

a step-like morphology is related to

Answer 41

retrogressive sliding

Question 42

t or f: step-like morphology includes presence of tension scarps

Answer 42

T

Question 43

are associated with the head part of a slide with the outcrop of a failure plane

Answer 43

semicircular niche

Question 44

semicircular niche are recognizable on photographs as a ________

Answer 44

light-toned scarp with small light curved lineaments

Question 45

back tilting of slope faces indicates

Answer 45

rotational movement of slide blocks

Question 46

back tilting of slope faces appear as

Answer 46

oval or elongated depressions with imperfect drainage conditions

Question 47

irregular slope morphology. micro relief associated with shallow movements or small retrogressive slide blocks

Answer 47

hummocky relief

Question 48

hummocky relief are associated with

Answer 48

shallow movements with retrogressive slide blocks

Question 49

t or f: the coarse surface texture of hummocky terrains stand in contrast with smooth surroundings

Answer 49

T

Question 50

morphological indication of recent activity

Answer 50

formation of cracks

Question 51

crack formation occurs with _______ movements

Answer 51

sliding and toppling

Question 52

t or f: cracks appear as lineaments more or less perpendicular to the existing scar

Answer 52

F (parallel)

Question 53

morphological indication of a presence of a landslide scar

Answer 53

steepening of slopes

Question 54

it is the top of a scar and would indicate the original slope if it is connected to the tip of the landslide

Answer 54

break point

Question 55

t or f: vegetational clearances coincide with morphological steps

Answer 55

T

Question 56

______ and _____ in a slide body often lack vegetation

Answer 56

headscarps and steps

Question 57

vegetational clearances on photographs shows as

Answer 57

light-toned elongated areas at the crown or on the body of mass movement

Question 58

_____ and ____ strip parts of the slope from vegetation; leaving the flowpath _____

Answer 58

flows and avalanches; uncovered

Question 59

t or f: slip surfaces of translational slides are uncovered with vegetation

Answer 59

T

Question 60

the denudated areas of irregular linear clearances are shown as

Answer 60

light tones, with linear pattern in direction of movement