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Coast exam questions (revision) (With reference to a case study, explain…
Coast exam questions (revision)
With reference to a case study, explain the influence of unintentional human activity on the coastal landscapes. (8)
Erosion of the beaches increases in comparison to before human activity
The rate of sand extraction is unsustainable
Beaches are starved of sediment and are becoming wider and flatter
Less effective at absorbing energy from the waves
Due to positive feedback, the beaches continue to become wider and flatter
Especially high energy waves
A coastal system has sediment cells which are examples of a closed system which is 'filled' with sand which is a non-renewable resource
Near shore mining of sand means that sediment is removed from the system meaning that outputs have increased and are not replaced by inputs from rivers and offshore waves
Total sand supply is depleted, in both beaches, dunes and the sea bed
Movements of sand between stores in the sediment cell have diminished significantly
Sand mining at pakiri beach exceeds inputs by a factor of 5
For 70 years, at both Mangawhai and Pakiri beaches 165,000m3 of sand have been extracted per year. extraction has stopped at Mangawhai but continues at 75,000m3/yr at Pakiri beach until 2020
A large proportion of this sand is used to replenish Aucklands tourist beaches
Using evidence from Fig. 1a and Fig.1b, compare and contrast the characteristics of the two cliffs shown.(4)
Figure 1 is a cave which is formed in soft rock as a weakness, usually a crack, is exploited
Fig. 1b has horizontal bedding planes which give a straighter cliff face whereas in Fig. 1a the rock at the end is more sloped
This creates cliffs which have different structures
Structure also indicates that the cliff in Fig. 1a has a weaker lithology as a cave has been eroded into the cliff
With reference to either Fig. 1a or Fig. 1b, explain how flows of energy have shaped the cliff. (3)
Fig 1a
Geology is soft so easily eroded by both
weathering and wave processes
Erosion - waves are a source of energy such as pounding from waves and wave refraction
Pounding - up to 30t/m2 can be exerted by high energy waves
Wave refraction concentrates the wave energy to one point of the rock
Abrasion also plays a role - waves with rock particles weather the rock and weaken it
