Landslide Classification

Question 1

definition of landslides

Answer 1

movement of a mass of rock, debris, or earth down a slope.

Question 2

are landslides limited to land?

Answer 2

no, can be submarine

Question 3

ground subsidence, collapse, ice falls or snow avalanches are all examples of landslides. TRUE/FALSE

Answer 3

False. they are not landslides

Question 4

are landslides 100% human initiated?

Answer 4

nope, they are part of the natural landscape forming. They are “accelerated erosion” if you will.

Question 5

main landslide causes

Answer 5

1. Natural (rivers, streams, waves)
2. weathering
3. geological (weak materials, e.g. rock)
4. rainfall
5. earthquake
6. human activity (slope modification)

Question 6

what important things must be recorded in a landslide event?

Answer 6

1. topographic location
2. site details
3. size of landslide feature
4. material type
5. activity
6. potential for future movement
7. photos

Question 7

how are landslides classified?

Answer 7

• mechanism of failure (mode of movement)

- type of material (rock and soil types)

Question 8

why do landslides need to be classified?

Answer 8

different landslides move at different speeds

Question 9

whats depth of failure surface in a shallow, and a deep-seated landslide

Answer 9

shallow < 5m

deep-seated > 5m

Question 10

trigger of most shallow landslides is…

Answer 10

rainfall

Question 11

deep seated triggered by….

Answer 11

faults, shears, etc.

Question 12

4 main types of landslide

Answer 12

1. falls
2. slides
3. avalanches (not snow)
4. debris flows

Question 13

falls

Answer 13

masses of rocks, soil, or debris moving rapidly down very steep slopes, by freefall or bouncing and rolling

Question 14

slides

Answer 14

rock, soil or debris sliding down planes of weakness (bedding, joints, faults, etc.)

Question 15

avalanches

Answer 15

rock and debris. Very rapid and long-run on steep slopes for than 200m high. Can be wet or dry flows or falls

Question 16

debris flows

Answer 16

high sediment concentrations (like wet concrete)

Question 17

are debris floods landslides?

Answer 17

nope.

Question 18

coarse soils debris size

Answer 18

> 2mm

Question 19

different types of landslide movement

Answer 19

1. slides
   - rotational
   - translational
2. spreads
3. flows
4. complex

Question 20

landslide scar

Answer 20

source area and debris trail

Question 21

main scarp

Answer 21

steep slope at the head of the slide (visible part of the failure surface)

Question 22

tension cracks

Answer 22

located upslope of main scarp.

Question 23

hummocky ground

Answer 23

irregular ground surface, results from shear and compression in the displaced material

Question 24

Is there a difference between rainfall and earthquake induced landslide occurrence?

Answer 24

earthquake induced are more likely on steep rock slopes ( would’t be any soils there - too steep)

Question 25

active landslides

Answer 25

currently moving or moved in the last year

Question 26

3 inactive landslide classifications

Answer 26

1. dormant - causes and potential for movement remain
2. Stabilised - remedial measures have stopped movement
3. Relict - developed under different conditions - prehistoric

Question 27

name of an inactive landslide that starts to move again

Answer 27

reactivated

Question 28

• eroded rounded and subdued features
• main scarp eroded and well vegetated
• hummocky and irregular ground with ponds.

What is being described here?

Answer 28

Relict landslide

Question 29

dormant landslide

Answer 29

causes and potential for movement remain