Slopes and Mass Movements

Question 1

What is Denudation?

Answer 1

wearing away of the landscape (exogenous)

Question 2

What is a Slope?

Answer 2

Inclined surface that forms a boundary between 2 landscape features

Question 3

How are slope angles formed?

Answer 3

Slope angles are formed as weathered material is pulled downward by gravity
-Primary reason for differences is that the stronger material is able to maintain a steeper angle

Question 4

What 3 forces must be overcome in order to move material?

Answer 4

Friction: resistence of movement by 2 passing objects
Inertia: something in motion wants to stay in motion, not moving wants to stay in place
Particle Cohesion: how well the pieces stick together

Question 5

How to friction, inertia and particle cohesion relate to slope?

Answer 5

Higher friction, inertia and particle cohesion = stronger = steeper slope (They are the 3 factors of Shear Strength)
-Sheer Stress: gravity interacting with the slope angle

Question 6

What is the Angle of Repose?

Answer 6

the angle that balances shear stress and shear strength

Question 7

Slope stability

Answer 7

Determined by shear stress & strength
Stable: shear strength able to maintain angle
Unstable: shear strength unable to maintain angle (movement)

Question 8

What could modify slope stability?

Answer 8

-changes in balance due to modification of slopes (rivers, road cuts, waves crashing on cliffs) or modification of shear strength (weathering, water, vegetation, shocks)

Question 9

Mass Movement Types

Answer 9

SLIDES: fine material sliding (cohesive)
FLOWS: coarse material (non-cohesive, more turbulent)
HEAVES: general, overall movement

Question 10

Rockfall

Answer 10

Source of rock up top (strong material = steep slope)

• weathering occurs
• Vertical drop (fast moving = wrong place, wrong time)

Question 11

Landslide

Answer 11

Transitional slide (dirt, etc = land)
Wetter would be a "Flow"

Question 12

Slump

Answer 12

• top drops downward

- relatively cohesive, dry

Question 13

Earthflow

Answer 13

• likely happening during rainy season
• rounded scar at top (origin)
• narrow connection
• rounded lobe at bottom
• fine material

Question 14

Debris Flow

Answer 14

• river of cement like mixture of mud, debris
• can be very devastating
• mud piles up on sides, pushes stuff down the middle
• coarse material
• flow

Question 15

Creep

Answer 15

very slow, gradual

Question 16

Solifluction

Answer 16

• type of creek in wet, cold area

- down slope movement, freeze/thaw