L8 - Mass Movement

Question 1

Define Mass Movement

Answer 1

“Processes transferring earth materials downslope under the influence of gravity without primary assistance of fluid transporting agent”

• Material moves en-masse in close, grain-to-grain contact

Question 2

List the 5 types of MM

Answer 2

Falls
Slides
Flows
Subsidence
Creep

Question 3

Define a Fall

Answer 3

“Free movement of soil or rock away from a steep slope”

Question 4

What 3 factors effect the size and shape of a fall?

Answer 4

• Rock weaknesses
• State of rock weathering esp. frost and precipitation
• Slope geometry

Question 5

What is a toppling failure?

Answer 5

“Rotation or overturning of blocks of material as they fall/creep from a cliff”

Question 6

What is a slide?

Answer 6

• Where debris moves en-mass downslope over a shear surface

- Shallow: Only 2-3m deep

Question 7

What are the causes of active-layer detachment slides?

Answer 7

• Permafrost
  
  • > Late-summer melting causes shearing
• Forest-fire, loss of stabilising trees

Question 8

What are the two main types of slide

Answer 8

• Active layer detachment slides

- Rotational slides

Question 9

What is a rotational slide?

Answer 9

• Where slide occurs over a curve, causing sediment to ‘rotation’

Question 10

What is a flow?

Answer 10

• Shears throughout moving mass

- No well-defined shear plane (a slurry)

Question 11

What are two types of flow?

Answer 11

• Solifluction
• Debris flows
  
  • Lahars(Volcanic)

Question 12

What are the two basic types of causes of mass movement?

Answer 12

• Factors promoting high shear stress

- Factors promoting low shear strength

Question 13

What is a very common cause of mass movement

Answer 13

• Water

Question 14

Broadly describe the geology of the southern part of the Isle of Wight

Answer 14

• Clay overlain with chalk

Question 15

What is Ventor built on?

Answer 15

• A landslide

Question 16

How does the council of the Isle of Wight try to management landslides?

Answer 16

• Geomorphological mapping
• Site investigations
• Damage surveys
• Determination of past movement rates
• Review of historical events

Question 17

What are the major types of submarine slides?

Answer 17

• Debris flow

- Turbidites

Question 18

When did the Storegga Slide occur? What did it cause?

Answer 18

• 8,200 ya

- Tsunami >20m

Question 19

What are the two main types of landslide in the Canary Islands?

Answer 19

• Debris avalanche (Rapid)

- Slumps (Gradual)

Question 20

What was the youngest Canary Island landslide?

Answer 20

• El Golfo, Island of El Hierro
• 15,000 ya
• Caused tsunami

Question 21

What was the deadliest landslide?

Answer 21

Soviet Union, 1949 - 12,000

Question 22

What was landslide was the most costly?

Answer 22

Brazil, 1966 - $4,000,000

Question 23

What was the costliest landslide?

Answer 23

Peru, 1983 - 988,800