hunan activity and coastal recession

Question 1

Name 2 geological factors affecting coastal erosion

Answer 1

lithology- soft rock type, weak cohesive bonds, porous rocks

geological structure- well jointed rocks, seaward dipping beds, heavily faulted rocks

Question 2

Name 2 marine factors affecting coastal erosion

Answer 2

• long wave fetch- promotes large destructive waves

- strong longshore drift- quickly removes collapsed sediment allowing erosion to restart

Question 3

How can human activity increase rates of coastal recession

Answer 3

by interrupting operation of the sediment cell

-e.g construction of major dams of rivers can trap river sediment behind dam wall- starvung coast of sediment

Question 4

what is dredging

Answer 4

removal of sediment from a beach, sea or river

Question 5

how do subaerial processes influence rates of coastal recession

Answer 5

weathering and mass movement processes work together

-e.g weathering weakens rocks making mass movement easier

Question 6

Name the 5 factors that affect the rate of recession

Answer 6

• wind direction/ fetch
• tides
• storms
• seasons
• weather systems

Question 7

How does wind direction and fetch influence rates of recession

Answer 7

• rates of recession are higher when wind is blowing onshore
• dominant wind- direction of strongest wind- often coincides with direction of largest fetch- increases rate of recession

Question 8

How do tides influence rates of recession

Answer 8

rates of recession- more rapid- during high tide- deeper water allows waves to maintain higher energy

-greater energy of impact on backshore increases erosion

Question 9

How do storms influence rates of recession

Answer 9

-produce large, high energy destructive waves- so fast rates of recession

Question 10

How do seasons influence rates of recession

Answer 10

-storm events more likely to occur in winter- contrast in temp and pressure

Question 11

Give an example in the UK of where rates of recession are faster in winter than in summer

Answer 11

-in Holderness- in winter 2-6m of erosion is common- when storms combine with tides

Question 12

Why do people choose to live in areas at risk from coastal flooding

Answer 12

• coastlines are densely populated as beaches and sea attract large numbers of tourists
• deltas are extremely fertile- good for farming
• deltas and estuaries are ideal locations for trade

Question 13

Name 4 local factors that increase flood risk on some low lying and estuarine coastlines

Answer 13

• height- low-lying coastlines are only 1-2m above seal level
• subsidence-
• vegetation removal-
• global seal level rise

Question 14

Name the 5 types of classification of mass movements

Answer 14

• fall- rocks dislogded by weathering/ hydraulic action- wave-cut notches lead to rockfall
• topple- geological structure- steep seaward dip undercut by erosion- instability- rocks topple
• translational slide- low angle seaward dip in strata prevents falls- encourages slides
• rotational slide/ slumping- huge masses of material slowly rotate downslope
• flow- common in weak rocks- clay, unconsolidated sands- materials become staurated and lose cohesion and flow downslope

Question 15

Explain the process of rotational slides

Answer 15

1- bedding plane between impermeable clay and permeable sand dips seaward- mass movement

2- cracks develop in cliff top- dry weather- soil and sediment dry out- routes rainwater can take into sand

3- heavy rain saturates permeable sands

4- water enters permeable sand- forced to move along sand boundary- clay impermeable- creates internal pressure in cliff

• toe erosion occurs (hydraulic action, abrasion)- undercuts cliff- instability
• rotational slide occurs