test 1 - mass movement and hillslopes

Question 1

What are the erosional forces

Answer 1

Driving and resistant forces

Question 2

Why might a material have a higher erosional rate

Answer 2

low resistance; driving forces higher than resistant forces

Question 3

In a rock, what does physical weathering lower

Answer 3

its strength

Question 4

What influences the shear strength of a rock

Answer 4

frictional characteristics:

• plane friction
• interlocking friction between grains (greater than plane friction)

Question 5

Effective NORMAL STRESS increases what in a rock

Answer 5

internal resistance to shear; compacts/holds the material together

Question 6

What does cohesion of a rock increase

Answer 6

The shear strength; through cementation

Question 7

What are the resistant forces

Answer 7

Frictional factors
Effective normal stress
Cohesion

Question 8

How does a solid behave like a plastic and why

Answer 8

overburden stresses/strains the underlying rock or sediment, if the overburden is removed the underlying rock may rebound to its original shape/expand, this rebound can cause movement downslope

If the stress on the material is great enough, it may be permanently deformed

Question 9

How does a sediment behave like a fluid

Answer 9

sediment can be filled with water or air and move without a high degree of internal friction

Question 10

What are the factors that INCREASE shear stress (driving forces)

Answer 10

Removal of lateral support

• erosion (river action, freeze/thaw, wave action, wind)
• human activity (road cuts, quarries)

Addition of mass

• natural (rain, talus)
• human caused (fills, ore stockpile, urbanization)

Earthquakes
   -lost of cohesion (shaking adds air/space)
Regional Tilting
Removal of underlying support
Weathering
Pore water
Structural changes

Question 11

What are the three types of basic hillslope movement (failures)

Answer 11

Slides
-cohesive blocks of material move on a well defined
plane; no internal shearing

Flows
-moves by differential shearing and mixing; no clear
plane at base of movement

Heaves
-expansion of material; creep; swelling and
contraction propagated by gravity; forces act
perpendicular to ground surface

Question 12

What are some resisting factors

Answer 12

vegetation, soil type, shear strength

Question 13

What are some driving forces

Answer 13

gravity, force of flowing water, freeze/thaw etc.

Question 14

What are the 4 major controls on slope form: TLCP

Answer 14

Time
Lithology
Climate
Process

Question 15

What are the models of slope development

Answer 15

Process model

Evolutionary model

Question 16

Explain the evolutionary model of slope development

Answer 16

slope depends on time and the slope decreased with time (erodes)

Question 17

Explain the process model of slope development

Answer 17

slope is time dependent
slope is dependent on material and slope process
-slope angle decreases with increased erodability of
rock type

Question 18

How does slope change according to evolutionary model vs process model

Answer 18

evolutionary model says time is the only factor for decrease in slope angle, process model takes into account slope material and its erodability over time.

Question 19

What type of slope are you likely to have with coherent resistant rocks

Answer 19

steep slopes

Question 20

If you have massive bedding will you have steep or shallow slopes

Answer 20

steep slopes

Question 21

Alternating strong and weak strata generate what type of slopes

Answer 21

irregular slopes

Question 22

If a strata has a high erodability, what angle is its slope likely to be

Answer 22

shallow slope/angle

Question 23

What is slope replacement

Answer 23

when the steepest angle is progressively replaced by upward expansion of gentler slope developed near the base