L8 - Mass Movement Flashcards
Define Mass Movement
“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
List the 5 types of MM
Falls Slides Flows Subsidence Creep
Define a Fall
“Free movement of soil or rock away from a steep slope”
What 3 factors effect the size and shape of a fall?
- Rock weaknesses
- State of rock weathering esp. frost and precipitation
- Slope geometry
What is a toppling failure?
“Rotation or overturning of blocks of material as they fall/creep from a cliff”
What is a slide?
- Where debris moves en-mass downslope over a shear surface
- Shallow: Only 2-3m deep
What are the causes of active-layer detachment slides?
- Permafrost
- > Late-summer melting causes shearing
- Forest-fire, loss of stabilising trees
What are the two main types of slide
- Active layer detachment slides
- Rotational slides
What is a rotational slide?
- Where slide occurs over a curve, causing sediment to ‘rotation’
What is a flow?
- Shears throughout moving mass
- No well-defined shear plane (a slurry)
What are two types of flow?
- Solifluction
- Debris flows
- Lahars(Volcanic)
What are the two basic types of causes of mass movement?
- Factors promoting high shear stress
- Factors promoting low shear strength
What is a very common cause of mass movement
- Water
Broadly describe the geology of the southern part of the Isle of Wight
- Clay overlain with chalk
What is Ventor built on?
- A landslide
How does the council of the Isle of Wight try to management landslides?
- Geomorphological mapping
- Site investigations
- Damage surveys
- Determination of past movement rates
- Review of historical events
What are the major types of submarine slides?
- Debris flow
- Turbidites
When did the Storegga Slide occur? What did it cause?
- 8,200 ya
- Tsunami >20m
What are the two main types of landslide in the Canary Islands?
- Debris avalanche (Rapid)
- Slumps (Gradual)
What was the youngest Canary Island landslide?
- El Golfo, Island of El Hierro
- 15,000 ya
- Caused tsunami
What was the deadliest landslide?
Soviet Union, 1949 - 12,000
What was landslide was the most costly?
Brazil, 1966 - $4,000,000
What was the costliest landslide?
Peru, 1983 - 988,800
