coasts

Question 1

what are the different areas of the coasts

Answer 1

backshore
foreshore
nearshore
offshore

Question 2

define backshore

Answer 2

begins at the high tide and ends at the furthest influence of the sea

Question 3

foreshore

Answer 3

begins at the low tide and ends at high tide

Question 4

nearshore

Answer 4

between low tide and low tide breaker line

Question 5

offshore

Answer 5

beyond the low tide breaker line

Question 6

how are waves formed

Answer 6

• wind pushes down on the water surface creating ripples
• on the leeward face of the ripple air is under low pressure and spreads out causing the leeward face to be pulled upwards
• the windward face is under high pressure and is forced downwards causing the wave to generate and increase in size

Question 7

what are the factors affecting wave size

Answer 7

wind speed
distance over which the wind has been blowing (fetch)
duration the wind has blown over a given area
water depth

Question 8

what is a constructive wave

Answer 8

• long wavelength
• low wave height
• depositional waves stronger swash than backswash
• (swell waves)
• low frequency 6-8 per minute
• associated with a low gradient coast

Question 9

what is a destructive wave

Answer 9

• erosional waves
• also called storm waves
• short wavelength/ high wave height
• high frequency 10-12 per minute
• associated with a steep gradient coast

Question 10

how do waves break

Answer 10

as the water depth decreases the bottom of the wave orbit changes from circular to elliptical and the base of the wave is slowed down and the top of the wave is still moving at the same rate, this causes top of the wave to plunge

Question 11

What is the relationship between the time of year and the gradient of a beach

Answer 11

• in the summer the wind is much calmer producing waves with less height and longer wavelength these are depositional waves which add beach sediment causing to have a low angle of rest
• in the winter the waves have much more energy and are destructive they plunge when they break causing the beach to have a steep angle of rest

Question 12

What are the differing erosion all rates of sandy beaches and shingle beaches

Answer 12

• Sandy beaches are eroded and deposited on by wave due to their low angle of rest and low percolation rates the wave energy can dissipate the sediment easier
• on a shingle beach there are high percolation rates so sediment can be thrown onto the beach but is unlikely to go back into the sea

Question 13

How do tides affect beach morphology

Answer 13

• depending on the position of the sun and moon the gravitational forces on the sea change. On coasts with low tidal range the beach is much narrower and therefore more susceptible to erosion
• beaches such as Britain with high tidal range has more shoreline exposed to wave action creating wider beaches less susceptible to erosion

Question 14

What is the definition of a sediment cell

Answer 14

A length of coastline in which sediment is self contained, the interruption of the movement in one cell does not affect the the adjacent cells

Question 15

How can constraining basins and amphidromic points affect the coastal erosion and deposition

Answer 15

• in a constraining basin the tide is forced into a narrowing basin and this increases the tidal range, therefore can also increase erosion rates
• amphidromic points cause the flood tide and ebb tide to flow in the same direction either accelerating erosion or deposition