Lecture 13 Flashcards Preview

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Flashcards in Lecture 13 Deck (23):
1

Is shear stress the driving or resisting force?

Driving

2

What is shear stress?

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

3

Is shear strength the driving or resisting force?

Resisting

4

What is shear strength?

Retaining force due to particle arrangement. Resisting force

5

What forced are at work in mass wasting?

Driving force (shear stress)

Resisting force (shear strength)

Force of gravity

Normal

6

What is pour water pressure?

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

7

What is the factor of safety?

Resisting force
---------------
Driving force

Strength
---------
Stress

8

When does a slope because unstable?

When the factor of safety is less than 1

9

What three factors control mass wasting?

Strength of slope materials
Slope over steepening
Water content

10

What can act as a triggering mechanism for mass wasting?

Earthquake

11

Is mass wasting natural?

Yes when a slope is trying to come back to equilibrium

12

What are the five roles of water in mass wasting?

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

13

What are the four main types of mass wasting?

Creep
Slump
Flows and slides
Falls

14

What distinguishes the four main types of mass wasting?

Speed
Material
Moisture

15

Define a soil creep.

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

16

Define solifluction.

Slow Downslope movement of saturated sediment lobes.

17

What differs gelifluction and solifluction?

Gelifluction occurs when ice is present

18

Define a slump.

Quick release of sediment in a rotational motion

19

Define a flow.

Movement of materials with high moisture very quickly

20

Define falls and slides.

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

21

What is the number one most fatal natural hazard?

Flooding

22

Do colder or warmer climates promote faster weathering?

Warmer

23

What is mass wasting?

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