2.1. Wave, marine and sub-aerial processes

Question 1

Define wave

Answer 1

• Waves are oscillation of the water surface
• Water does not move forward

Question 2

Define wave height/amplitude

Answer 2

The distance between the trough and the crest Indication of wave energy

Question 3

Define wavelength

Answer 3

The distance between successive crests or troughs

Question 4

Define wave frequency

Answer 4

The number of waves per minute

Question 5

2 Factors affecting the formation and size of a wave

Answer 5

1. Wind velocity
2. Depth of water Fetch - the distance of open water the wave travels over

Question 6

What are the coastal zones? (3)

Answer 6

1. Upper beach/backshore - backed by cliffs or sand dunes
2. Foreshore - periodically exposed by tides
3. Offshore - covered by water

Question 7

Define wave orbit

Answer 7

• The shape of the wave. Varies between circular and elliptical. The orbit diameter decreases with depth (roughly equal to wavelength)

Question 8

Define wave base

Answer 8

When the orbit diameter decreases to a point there is no further movement related to wind energy

Question 9

Define swell waves

Answer 9

Waves that are characterised by lower height and longer wavelength

Question 10

Define wave breaker

Answer 10

Occurs when waves move further onshore, friction slows down the wave advance causing the shortening of wave

Question 11

What are the 3 main types of breaker?

Answer 11

1. Spilling breakers
2. Plunging breakers
3. Surging breakers

Question 12

What are spilling breakers?

Answer 12

• Are associated with gentle beach gradients and steep waves are characterised by gradual peaking of the wave until the crest becomes unstable => gentle pilling forward of the crest

Question 13

What are plunging breakers?

Answer 13

• Tend to occur on steeper beaches than spilling breakers with waves of intermediate steepness distinguished by the shore ward face of the wave becoming vertical, curling over and plunging forward.

Question 14

What are surging breakers?

Answer 14

• Found on steep beaches with low steepness waves, the front face and crest of the wave remain relatively smooth a large proportion of the wave energy is reflected at the beach

Question 15

Define swash, backwash

Answer 15

1. Swash: forward movement of water up the beach
2. Backwash: backward movement of water down the beach

Question 16

Define constructive waves/swell waves (6)

Answer 16

• Swash is greater than backwash
• Large fetch
• Long wave length
• Low height
• Found on low gradient beaches, low energy waves which deposit materials
• Associated with spilling breakers

Question 17

Define destructive waves/stom waves (6)

Answer 17

• Backwash is greater than swash
• Short fetch
• Short wave length
• High waves and frequency
• Steeply sloping beaches
• High energy waves which erodes

Question 18

Define tide

Answer 18

• regular movements in the sea’s surface, caused by the gravitational pull of the moon and sun on the oceans
• Low spring tides occur just after a new moon
• Hgh spring tides occur after a full moon

Question 19

Define tidal range

Answer 19

The difference between high and low tide

Question 20

3 types of rides coastal areas can be classified into?

Answer 20

1. Microtidal
2. Mesotida: 2-4m
3. Macrotidal - > 4m

Question 21

Define storm surges ( bão lao tới/ bão dâng lên)

Answer 21

• Changes in the sea level caused by intense low pressure systems and high wind speeds for every drop in air pressure of 10mb sea water is raised 10 cm

Question 22

Define wave refraction

Answer 22

• Is the change in speed and distortion of wave
• Waves are refracted and energy is concentrated around headlands and more dispersed (phân tán) along beaches located in:
• Bays headland - converging waves, deeper waters (erosion)
• Bay - diverging waves, shallower waters (deposition)

Question 23

4 types of erosion

Answer 23

1. Hydraulic action: water breaks against cliff face, air trapped in cracks and joints => cavitation
2. Corrasion/Abrasion: process whereby breaking wave can hurl pebbles and shingle against a coast and thus abrading it
3. Attrition
4. Solution

Question 24

5 Mass movements occur in coasts

Answer 24

1. Salt weathering
2. Freeze thaw weathering
3. Biological weathering
4. Solution weathering
5. Slaking ( sự dập tắp )

Question 25

Salt weathering

Answer 25

the process by which **sodium** and **magnesium** compounds **expand in joints** and **cracks =\> weakening** rock structures

Question 26

Freeze-thaw weathering

Answer 26

The process whereby **water freezes,** **expands** and degrades (giảm bớt) jointed rocks

Question 27

Biological weathering

Answer 27

Carried out by **molluscs**, s**ponges** and **sea urchins** that burrow (đào bới)

Question 28

Solution weathering

Answer 28

The chemical weathering of **calcium** by **acidic** water

Question 29

Slaking ( làm dãn ra)

Answer 29

Materials disintegrate (phân tán) when exposed to water

Question 30

2 Energy factors affecting the rate of erosion

Answer 30

1. **Waves -** **wave steepness** (steep destructive waves have more erosive power) and **wave breaking point** (where wave break at cliff base that cause maximum erosion) 2. **Tides Currents Winds** - **onshore wind**s erode **fine beach materia**l, **offshore winds** erode **dunes**

Question 31

4 Material factors affecting the rate of erosion

Answer 31

1. Sediment supply - continual supply -\> **abrasion. oversupply can protect the coast** 2. Beach/rock platform width - absorb wave energy 3. Rock resistance 4. Rock structure - well jointed

Question 32

Shore geometry factors affecting rate of erosion (3)

Answer 32

1. **Offshore topography** - **steep seabased** creates **higher** and **steeper waves**; l**ongshore bars** cause **waves to break offshore** and l**ose energy** 2. **Orientation of coast** - **headlands** with **vertical cliffs** tend to **concentrate wave energ**y by refraction 3. **Direction of fetch** - longer **the fetc**, greater potential for erosion

Question 33

How is the sediment transport categorised? (2)

Answer 33

2 modes: 1. **Bedload** - **grains transported** by bedload are moved t**hrough continuous traction** or **discontinuous saltation** 2. **Suspended load** - grains are **carried by turbulent flow** and **held up by wate**r. **Strong currents**

Question 34

Define sediment cells (2)

Answer 34

1. A section of the **coastal zone** here the **sediment** in the **nearshore zone** is moved by **longshore drift** 2. **Sediment cells** have **clear boundarie**s to define them such as headlands

Question 35

4 Inputs to sediment cell

Answer 35

* **Cliff** erosion * **offshore** bars * **river** sediment * **sand dunes** eroding -\> depositional feature *e.g. beach*

Question 36

Transportation in a sediment cell (4)

Answer 36

1. **Longshore** drift 2. **saltation** 3. **traction** 4. **suspension**

Question 37

Stores of a sediment cell (1-3) (2-1)

Answer 37

1. **temporary** features - beaches, dunes and spits 2. bars **permanent** stores - estuary

Question 38

Notes about sediment cell

Answer 38

* In reality it is **unlikely that sediment cells are fully closed**. With **variations** in **wind directions** and **tidal currents**, it is **inevitable** that some **sediment is transferred between cells**

Question 39

Define **dynamic equilibrium** (2)

Answer 39

1. The concept states that any system (sediment cell for example) is the **result of the inputs** and **processes** that **operate within it.** 2. **Change to one of the input**s will cause a **knock on effect** on t**he process** and resulting a c**hange** in **the landforms**. *e.g. increase in sediment =\> **beach protetion** =\> **stabilisation** of cliffs*