Sources of coastal energy and low energy coasts

Question 1

How does prevailing wind direction impact the waves?

Answer 1

• controls direction that waves approach the coast from

- controls direction of transport of material

Question 2

What is fetch?

Answer 2

distance of open water over which a wind blows uninterrupted by major land obstacles

Question 3

How does fetch affect waves?

Answer 3

• helps determine magnitude and energy of waves reaching the coast
• helps create the waves

Question 4

What does fetch act as an agent of?

Answer 4

erosion

Question 5

What is the primary agent that shapes the coast?

Answer 5

waves

Question 6

What is wave height?

Answer 6

difference between a wave crest and trough

Question 7

What is wavelength/amplitude?

Answer 7

distance between successive crests

Question 8

What is wave frequency/period?

Answer 8

time between one crest and the next

Question 9

What is backwash?

Answer 9

water receding back down the beach towards the sea

Question 10

What is swash?

Answer 10

rush of water up the beach after a wave breaks

Question 11

What are features of constructive waves?

Answer 11

• low wave height
• long wavelength
• low frequency (6-8/min)
• swash more powerful than backwash

Question 12

What are features of destructive waves?

Answer 12

• high wave height
• steep form
• high frequency (10-14/min)
• stronger backwash than swash

Question 13

What is wave refraction?

Answer 13

• as waves approach the coast, they drag in the shallow water that meets the headland
• the part of the wave in deeper water moves faster, so causes the wave to bend

Question 14

As waves drag in shallow water, what does this impact?

Answer 14

• increase wave height
• increase steepness
• shortens wavelength

Question 15

What is the overall effect of wave refraction?

Answer 15

• wave energy becomes concentrated on the headland, causing greater erosion
• low-energy waves spill into the bay, resulting in beach deposition

Question 16

What are currents?

Answer 16

• the permanent or seasonal movement of surface water in seas/oceans

Question 17

What are longshore currents?

Answer 17

• occur as waves approach the coastline at an angle

- generates a current running parallel to coastline

Question 18

What are rip currents?

Answer 18

• strong currents moving away from the shoreline

- develop when seawater is piled up along the coastline by incoming waves

Question 19

What is upwelling?

Answer 19

• movement of cold water from deep in the ocean towards the surface
• denser, cold water replaces warmer surface water
• these currents form part of the pattern of global ocean circulation currents

Question 20

What are tides?

Answer 20

• periodic rise and fall in the level of the sea

Question 21

What are tides caused by?

Answer 21

• gravitational pull of the sun and moon

Question 22

What is spring tide?

Answer 22

• twice a month (when sun, moon and earth are in a straight line)
• highest monthly tidal range

Question 23

What is neap tide?

Answer 23

• twice a month (when moon and sun are positioned 90 degrees perpendicular to each other in relation to the earth)
• lowest monthly tidal range
• high and low tides are between 10-30% lower than average

Question 24

What are tidal/storm surges?

Answer 24

• occasions when meteorological conditions give rise to strong winds which can produce much higher water levels than those at high tide

Question 25

What are depressions?

Answer 25

• intense, low pressure weather systems
• over North sea
• produce conditions that have the effect of raising sea levels
• strong winds cause waves to pile up along the coast

Question 26

What are low energy coastlines?

Answer 26

• coastlines where wave energy is low

- rate of deposition often exceeds the rate of erosion

Question 27

What are typical landforms of low energy coastlines?

Answer 27

• beaches and spits

Question 28

Usually where are low energy coasts?

Answer 28

• estuaries
• inlets
• sheltered bays