waves and beach profiles

Question 2

describe the characteristics of constructive waves

Answer 2

• short wave height
• long wave length (fetch)
• swash > backwash
• low energy
• deposition > erosion

Question 3

define a tide

Answer 3

the rise and fall of the sea level

Question 4

what causes tides?

Answer 4

caused by gravitational pull of the moon (some extent is also caused by the sun)
- when the sun and the moon align = biggest gravitational pull = highest tides
- this is a major problem during storms as it increases their intensity

Question 5

where in the UK experience the largest waves?

Answer 5

Cornwall - this is because the waves here have a very long fetch as they have travelled across the whole Atlantic ocean from Florida which is over 4000km

Question 6

how are storm surges created?

Answer 6

• during high tides
• when there are strong onshore winds = high levels of wave energy
• during low pressure weather systems which allow the sea to expand forcing an increased volume of water on land, and offshore in the form of bulges

Question 7

why are bulges a problem in the North sea?

Answer 7

this excess volume of water is forced down into the English channel which can cause an increased risk of flooding

Question 8

when did the last ice age end and what happened when the glaciers melted?

Answer 8

• 40,000 years ago
• the melting of the glaciers lead to eustatic rise in the oceans causing the area of “doggerland” which cut the UK off from mainland Europe

Question 9

what factors determine the size of a wave?

Answer 9

• strength of the wind
• duration that wind blows for
• water depth
• wave fetch

Question 10

how is a wave created?

Answer 10

• a wave is created through the friction between wind and water surface
• it is the transfer of energy from wind into water from one particle to the next through a circular orbit
• this transfer of energy generates ripples in the water which grow into waves

Question 11

how does a wave break?

Answer 11

• when waves reach a depth of half their wavelength, the orbital motion hits the seabed
• friction between the seabed distorts the wave from the circular orbit to elliptical orbit
• more shallow = slower velocity
• wave crest has higher velocity than wave trough causing the wave to collapse
• it breaks in the near shore zone and travels up the beach as swash
• gravity then slows the wave and it retreats as backwash.

Question 12

define the wave height

Answer 12

the vertical distance between peaks and troughs

Question 13

define the wave length

Answer 13

the horizontal distance from crest to crest

Question 14

define wave frequency

Answer 14

the number of waves passing a given point over a given time period

Question 15

describe the characteristics of destructive waves

Answer 15

• erosion> deposition
• back wash > swash
• short wave length
• high energy
• narrow beaches
• steeper gradient beaches

Question 16

what type of wave is typically found on a shingle beach? why?

Answer 16

a destructive wave
- this is because they have more energy to carry a heavier load up the beach
- the gaps between the rocks increases erosion as the water flows through the gaps
- no backwash because the water moves under the rocks

Question 17

what sediment type is typically found on a constructive wave beach?

Answer 17

smaller and lighter sediment

Question 18

what sediment type is typically found on a destructive wave beach?

Answer 18

bigger and heavier sediment (shingle)

Question 19

describe the beach profile for a constructive wave beach

Answer 19

gentle
slight seasonal change

Question 20

describe the beach profile for a destructive wave beach

Answer 20

• steep first section
• more gentle gradient at the back of the beach
• does experience seasonal change - in the winter there are more storms so the waves have more energy than in summer months