2.8(Spec2) - Mass Movement + Barton

Question 1

Examples of stresses on a cliff?

Answer 1

• Angle of slope
• Rainwater/saturation
• Vibration
• Earthquakes
• Undercutting (sea/cliff erosion)

Question 2

Examples of strengths on a cliff?

Answer 2

• Tree/vegetation roots
• Porosity of soil
• Consolidation of material
• Lubricant layers (allow water to flow through cliff and out to side)

Question 3

What are the types of mass movement?

Answer 3

• blockfall
• topple
• translational slide
• (rotational) slumping
• flow / landslides

Question 4

What is blockfall/rockfall?

Answer 4

• Rapid mass movement
• When rocks are dislodged by mechanical weathering/HA
• Also when cliffs are undercut, leading to large block falls

Question 5

What are topples?

Answer 5

• Rock strata has very steep seaward dip
• Is undercut by erosion
• Will lead to instability and blocks of material toppling into sea
• subject to geology

Question 6

What are translational slides?

Answer 6

Very low angle seaward dip (no blockfall)
Material slides down dipslope

Question 7

What is a flow/landslide?

Answer 7

• flow of unconsolidated material downslope
• material becomes saturated, thus loses cohesion
• can be caused by heavy rainfall and high tides which saturate weak rocks (clay and unconsolidated sand)

Question 8

What is (rotational) slumping?

Answer 8

• Movement of material along a curved failure surface (seaward bedding plane)
• water lubricates slip plane along impermeable/permeable boundary
• can occur over days to years

Question 9

What are block slides?

Answer 9

• material slides down along a bedding plane
• in large blocks

Question 10

What is a terrace?

Answer 10

Vegetation present at top of slump

Question 11

What is a back scar?

Answer 11

Exposed, curved surface along slip plane on cliff face

Question 12

How can mass movement be managed?

Answer 12

• Absorb wave energy:
  
  • Sea walls
  • Beach nourishment
  • Dune regeneration
• Boreholes - reduce internal water pressure of cliff, slip plane is not lubricated, upper layers are not as saturated

All reduce stress on cliff

Question 13

What is the downside of using dune regeneration?

Answer 13

Takes time to regenerate dunes
- need to wait for marram grass to grow

Question 14

What is the disadvantage of using beach nourishment?

Answer 14

Groynes are needed
- in order to keep sediment there

Question 15

What sort of coastline is Highcliffe/Barton Sands on?

Answer 15

• Concordant coastline

Question 16

How high are cliffs at Highcliffe?

Answer 16

• 25-35m

Question 17

What is the average erosion rate at Highcliffe/Barton-on-Sea?

Answer 17

• 1m/yr

Question 18

What has Barton-on-Sea been used for?

Answer 18

• testing hard engineering geology experiments
  
  • eg. Revetments, boulders, groynes