Chapter 15

Question 1

Landslide

Answer 1

sudden event where large quantities of rock move downhill

Question 2

mass wasting

Answer 2

downslope movement of rock, regolith, and soil under the direct influence of gravity

Question 3

most rapid and spectacular mass-wasting events occur in

Answer 3

areas of rugged, geologically young mountains

are changed to more subdued terrain

Question 4

role of water

Answer 4

when sediment pores fill with water, cohesion among particles are destroyed
Water can lubricate materials
water adds weight to a mass of material

Question 5

dry sand grains

Answer 5

bound mainly by friction to one another

Question 6

damp sand grains

Answer 6

small amounts of water increase the cohesion

Question 7

wet sand grains

Answer 7

saturation reduces friction and causes the sand to flow

Question 8

Heavy rains trigger

Answer 8

debris flow

Question 9

angle of repose

Answer 9

unconsolidated granular particles assume a stable slope

Question 10

mass wasting can be triggered by

Answer 10

oversteepened slopes that are unstable; ex: stream cuts, oversteepen slope

Question 11

landslides without triggers

Answer 11

slope material weakens over time

some landslides are random, unpredictable events

Question 12

fall

Answer 12

the free fall of detached pieces

Talus slopes are built by rock falls

Question 13

slide

Answer 13

occurs when there is a distinct zone of weakness separating the slide material from the underlying material

Question 14

rotational slide

Answer 14

surface of rupture is concave up

Question 15

translational slide

Answer 15

material moves long a flat surface

Question 16

flow

Answer 16

occurs when material moves downslope as a viscous fluid

Question 17

rock avalanche

Answer 17

most rapid type of mass wasting

rocks float on air as they move downslope

Question 18

creep

Answer 18

moves particles a few milimeters per year

Question 19

slump

Answer 19

movement of mass of rock or unconsolidated material as a unit along a curved surface

occurs along oversteepened slopes

Question 20

rockslide

Answer 20

occurs when blocks of bedrock slide down a slope

• fast and destructive
• triggered by earthquakes, rain or melting snow, common during spring

Question 21

debris slide

Answer 21

occurs when unconsolidated material slides down a slope

Question 22

debris flow

Answer 22

rapid form of mass wasting that involves the flow of soil and regolith with water
often confined to channels and canyons

Question 23

Lahar

Answer 23

debris flows composed mostly of volcanic materials

Question 24

Earthflows

Answer 24

form on hillsides in humid regions during heavy precipitation or snowmelt
commonly involve materials rich in clay and silt

Question 25

solifluction

Answer 25

downslope movement of water logged soils | Common in regions uderlain by permafrost

Question 26

permafrost

Answer 26

permanently frozen ground | especially around arctic ocean