2B.4

Question 1

Define beach morphology

Answer 1

The surface shape of the beach

Question 2

State the characteristics of constructive waves
(to include height, wavelength, frequency, swash)

Answer 2

Low height, long wavelength
6-8 per minute
Uninterrupted swash, starts at nearshore
Strong swash results in sediment berm
Shingle beach has percolation, so even less backwash, so steeper beach
depositional

Question 3

State the characteristics of destructive waves
(to include height, wavelength, frequency, swash)

Answer 3

High height, short wavelength
13-15/minute
Slower waves approach steep beach / storms
Still circular motion, so mass of wave goes down onto the beach
Sandy beach has less percolation, so even stronger backwash, so more damage
erosional

Question 4

What do constructive/destructive waves have an effect on

Answer 4

Beach morphology and beach sediment profiles

Question 5

How do c/d waves affect beach morphology and beach sediment profiles on different TEMPORAL (time) scales

Answer 5

Seaonally – different dominance of constructive (summer) and destructive (winter)

Daily – plunging waves become swell waves

Annually –
reduced river sediment – building of dams
Coastal management – restricts supply of onshore sediment
Climate Change – storms bring destructive waves / winter beach profiles

Question 6

What are swell waves

Answer 6

Waves that originate in mid ocean are larger swell waves (bigger than locally generated waves)

Question 7

What does beach morphology depend on

Answer 7

Changes in waves

Question 8

Why are beach profiles steeper in summer

Answer 8

• swash of constructive waves deposits larger material at the top of the beach, creating a berm
• as berm builds the backwash becomes weaker so beach material becomes smaller towards the shoreline

Question 9

How are berms eroded by plunging destructive waves in the winter

Answer 9

• Strong backwash transports sediment offshore, depositing it as offshore bars
• the backwash can exert an undertow dragging sediment back as the next wave arrives over the top

Question 10

What coastal landforms does erosion create

Answer 10

wave cut notches, wave cut platforms, cliffs, the cave-arch-stack- stump sequence

Question 11

How does a headland turn into a cave

Answer 11

• Starts with a headland / land sticking out in the sea
• The headland makes the waves refract.
• Erosion processes are concentrated on weak points on the sides of the headland, widening faults
•Hydraulic action / abrasion then form caves on the side

Question 12

How does a cave turn into an arch followed by a stack

Answer 12

• The cave will widen due to both marine erosion and sub-aerial processes,
- The caves meet, forming a tunnel
• The tunnel becomes an arch, which gets bigger and bigger
• The top of the arch collapses, leaving a pillar of rock (stack) as the arch can no longer support its own weight

Question 13

How does a stack become a stump

Answer 13

• Waves erode the base, particularly in storms, cutting into the stack
• Stack becomes unstable, collapses
- Leaves a base (stump), visible at low tide, submerged at high tide.

Question 14

How does a wave cut notch form

Answer 14

• Starts at the base of a cliff
• Cliffs are vertical slopes
• Breaking waves (swash) erodes away at the cliff material
• A curved-notch forms along the length of the cliff between high tide height and low tide height
• (At weaker points you might get caves)

Question 15

How does a wave cut notch turn into a wave cut platform

Answer 15

• The rock above is unsupported and eventually collapses under gravity
• Cliff line retreats (recession)
• Leaving behind a flat / slightly sloping area of rock – a shore platform
• This platform is subject to weathering and erosion
• Platforms could be left with so lots of rock pools or small ridges where rock is less / more resistant

Question 16

State an example of the cliff, cave, arch, stack and stump series

Answer 16

Gull’s point and sliding cove

Question 17

What is a blowhole

Answer 17

pot hole on top of a cliff​, created by chemical weathering, and ​a cave​, formed by marine erosion. As the cave erodes deeper into the cliff face and the pothole deepens, they may meet. In this case, a channel is created for incoming waves to travel into and up the cliff face (occasionally water splashes out of the top of the blowhole when energetic waves hit the cliff face).

Question 18

Seasonal variation in beach profiles and morphology in uk

Answer 18

1) Destructive, high-energy waves dominate in the winter, lowering angle of beach profile and spreading shingle over the whole beach. Offshore ridges/bars formed by destructive wave erosion and subsequent deposition of sand and shingle offshore.

2) In summer, constructive, low-energy waves dominate, steepening beach angle and sorting particles by size, with larger shingle particles towards back of beach. ​​In summer, constructive waves build berm ridges, typically of gravel/shingle at high tide mark

Question 19

monthly variation in beach profiles and morphology in uk

Answer 19

​-Tide height varies over course of lunar month, with highest high tide occurring twice a month at spring tide and two very low high tides (neap tides)​
As month progresses from spring down to neap tide, successively lower high tides may produce a series of berms at lower and lower points down the beach.
Once neap tide passes and move towards next spring tide, berms successively destroyed as material pushed further up beach by rising swash reach.

Question 20

daily variation in beach profiles and morphology in uk

Answer 20

Storm events during summer will produce destructive waves that reshape beach profile in a few hours.
Calm anticyclonic conditions in winter can produce constructive waves that begin to rebuild beach, steepening profile for few days before storm. ​
Destructive waves change to constructive ones as the wind drops.
Storm beaches, high at the back of the beach, result from high energy deposition of very coarse sediment during the most severe storm