Lecture 13

Question 1

Is shear stress the driving or resisting force?

Answer 1

Driving

Question 2

What is shear stress?

Answer 2

The downslope force from gravity acting on mass slope. Driving force

Question 3

Is shear strength the driving or resisting force?

Answer 3

Resisting

Question 4

What is shear strength?

Answer 4

Retaining force due to particle arrangement. Resisting force

Question 5

What forced are at work in mass wasting?

Answer 5

Driving force (shear stress)

Resisting force (shear strength)

Force of gravity

Normal

Question 6

What is pour water pressure?

Answer 6

The strength of water in a matrix. When it is negative there is suction, when it is positive there is buoyancy.

Question 7

What is the factor of safety?

Answer 7

Driving force

Stress

Question 8

When does a slope because unstable?

Answer 8

When the factor of safety is less than 1

Question 9

What three factors control mass wasting?

Answer 9

Strength of slope materials
Slope over steepening
Water content

Question 10

What can act as a triggering mechanism for mass wasting?

Answer 10

Earthquake

Question 11

Is mass wasting natural?

Answer 11

Yes when a slope is trying to come back to equilibrium

Question 12

What are the five roles of water in mass wasting?

Answer 12

Lubrication (reduces friction)
Erosive agent (direct removal)
Added weight (1000x more dense than air)
Positive pour water pressure (buoyancy)
Dissolves cohesive agents (clays minerals)

Question 13

What are the four main types of mass wasting?

Answer 13

Creep
Slump
Flows and slides
Falls

Question 14

What distinguishes the four main types of mass wasting?

Answer 14

Speed
Material
Moisture

Question 15

Define a soil creep.

Answer 15

Slow gradual down slope movement of surface material, low water content.

Question 16

Define solifluction.

Answer 16

Slow Downslope movement of saturated sediment lobes.

Question 17

What differs gelifluction and solifluction?

Answer 17

Gelifluction occurs when ice is present

Question 18

Define a slump.

Answer 18

Quick release of sediment in a rotational motion

Question 19

Define a flow.

Answer 19

Movement of materials with high moisture very quickly

Question 20

Define falls and slides.

Answer 20

Rapid movement of material either through air (fall)or down a slope (slide)

Question 21

What is the number one most fatal natural hazard?

Answer 21

Flooding

Question 22

Do colder or warmer climates promote faster weathering?

Answer 22

Warmer

Question 23

What is mass wasting?

Answer 23

The downslope movement of earth material. It occurs when the driving force exceeds the resisting force