Geology 101 Quiz 10

Question 1

mass wasting

Answer 1

large-scale movement of rock or sediment down slope

Question 2

the terminology for mass wasting events is based on three criteria

Answer 2

nature of motion, material, speed

Question 3

natures of motion as they apply to mass wasting events

Answer 3

fall (freefall)
slide (mass stays intact and moves down-slope as a unit)
flow (mass moves a fluid)

Question 4

materials as they apply to mass wasting events

Answer 4

rock, unconsolidated material (non-lithified sediment)

Question 5

speed as it applies to mass wasting events

Answer 5

slow (creep and solifluction)
moderate (slides, slumps, and flows)
fast (falls and avalanches)

Question 6

creep

Answer 6

slow, uniform movement of soil

Question 7

solifluction

Answer 7

creep of saturated soil over permafrost

Question 8

permafrost

Answer 8

ground that remains frozen all year

Question 9

how does solifluction occur

Answer 9

melting ice and snow during the summer saturates the soil on top of the permafrost; the saturated soil slowly flows down the slope forming rounded lobes

Question 10

slump

Answer 10

slow or fast displacement of block

Question 11

slide

Answer 11

movement of block parallel to surface (most common where thin rock layers are sloped and eroded)

Question 12

flow

Answer 12

fast; debris becomes fluidized by water or air

Question 13

fall/avalanche

Answer 13

free falling from cliff (fall) or bounding down steep slope (avalanche)

Question 14

influences on slope stability

Answer 14

steepness of slope, composition, vegetation, water content,

Question 15

steeper slopes are (less/more) stable

Answer 15

less

Question 16

consolidated material is (less/more) stable

Answer 16

more

Question 17

physical and chemical weathering weaken rock making is (less/more) stable

Answer 17

less

Question 18

(smaller/larger) particles make LESS stable slopes

Answer 18

smaller

Question 19

(rounded/angular) particles make LESS stable slopes

Answer 19

rounded

Question 20

angle of repose

Answer 20

the maximum slope angle unconsolidated material can maintain

Question 21

a stack of marbles will have a ? angle of repose

Answer 21

very low

Question 22

a stack of angular fragments will have a ? angle of repose

Answer 22

high

Question 23

fine sand has a (lower/higher) angle of repose than coarse sand

Answer 23

lower

Question 24

vegetation generally (decreases/increases) slope stability and why?

Answer 24

increases; a network of roots through the soil

Question 25

exceptions to vegetation increasing slope stability

Answer 25

root action that increases weathering, and heavy trees adding weight to an already weak overhang

Question 26

increasing the water content generally (decreases/increases) slope stability, but not always

Answer 26

decreases

Question 27

a small amount of water causes particles to adhere to each other due to surface tension, resulting in

Answer 27

a higher angle of repose

Question 28

excess water eliminates air spaces resulting in loss of surface tension and reduces friction between particles; thus, the angle of respose is

Answer 28

much lower

Question 29

heavy rains or raising the water level in a reservoir can ?; caves are an exception

Answer 29

destabilize weakened rock slopes

Question 30

caves are (less/more) stable when completely filled with water and why?

Answer 30

more; the water helps support the roof

Question 31

a cave with a thin or weak roof may collapse when

Answer 31

the water level drops below the top of the cave

Question 32

flooding

Answer 32

mass wasting causing flooding, and flooding causing mass wasting

Question 33

examples of mass wasting causing flooding

Answer 33

Gros Ventre River, Wyoming, 1925; Vaiont Dam, Italy, 1963

Question 34

liquefaction

Answer 34

liquefying saturated sediments by vibration (vibration is typically achieved by earthquakes)

Question 35

? and ? are the most commonly susceptible to liquefaction during earthquakes

Answer 35

sands and silts

Question 36

examples of liquefaction

Answer 36

1964 large earthquake in Alaska caused it in Alaska and Japan; 2004 earthquake in Japan

Question 37

quick clay

Answer 37

unstable clay that can suddenly liquefy and flow

Question 38

quick clay is formed when

Answer 38

marine clay with a high salt content is uplifted and leached by freshwater

Question 39

example of quick clay

Answer 39

Rissa, Norway: a farmer dug a pit to extend a barn and placed the removed sediment near the edge of a lake, causing underlying clay to suddenly give way and flow like water into the lake; Canada over 250 known slides have been attributed to quick clays (one in 1908 in Quebec killed 33)

Question 40

most quick clays are found in

Answer 40

northern countries once covered with continental glaciers