Waves, Tides, Sediments, Cells

Question 1

What are waves caused by

Answer 1

The surface of the sea exerting frictional drag on the lowest layer of the wind

Question 2

How are waves created

Answer 2

Higher layers move faster over the lower levels and fall foward, pushing down on the sea surface

Question 3

What does the height of the wave indicate, and what does it depend on

Answer 3

Indication of energy
Depends on the fetch, strength of the wind, duration of the wind and sea depth

Question 4

What are swell waves

Answer 4

Strong waves create steep waves which will decrease in height and increase in wavelength when winds ease

Question 5

What is wave refraction

Answer 5

Undersea topography causes wave fronts to slow, bend and aim to break parallel to shore

Question 6

Where is wave refraction most commonly found

Answer 6

Headland and Bay Coastline
Energy tends to concentrate on the headlands (more erosion) and lower energy in the bays (deposition). LSD occurs if the wave breaks at an angle within the bays

Question 7

Constructive/spilling waves characteristics

Answer 7

Long wavelength
Low in height
Strong swash pushes Sediment up the beach
Backwash soaks into beach on return. Sediment not pulled back
Lower energy waves, commonly swell
6-10/ minute
Most effective over a gentle shelving sea bed

Question 8

Destructive/spilling waves characteristics

Answer 8

Short wave length
Steep wave faces
High wave height
Wave crashes downwards into the with little swash
Backwash very strong, drags material down the beach
Backwash interferes with swash of next wave
Higher energy waves generate localised storm conditions
11-15/minute
Most effective over a steeply shelving sea bed causing a rapid increase in friction and a steep wave front

Question 9

Influence of waves and sediments on beach morphology dependant on factors

Answer 9

Wave type
Energy
Sediment type
Sea bed morphology

Question 10

Relationships between the influence of waves and sediment on beach morphology

Answer 10

Sand forms wide gentle gradient beaches
Constructive waves carry material up the beach
Destructive waves have a high energy backwash drawing material down the beach
Swash stronger than backwash on shingle beach - high percolation rates
Sandy beaches strong swash and long run up due to the flat profile. Similar strength backwash (low percolation). Material moved down the beach but returned with the next wave
Sediment moves up shingle beach. High percolation on the backwash to weak to remove sediment
Finer sediment doesn’t require as much energy to be eroded and transported. Higher energy environments have coarse sediment sizes

Question 11

Why are Sandy beaches eroded badly in the winter

Answer 11

Destructive waves are combined with a gentle sandy profile. Low percolation rates so material can be dragged from the beach as smaller particles don’t need as much energy to be transported.

Question 12

What ate oceans tides controlled by

Answer 12

Gravitational pull of the moon. Moon pulls water towards it, creating a bulge of water (high tide). Moon also pulls earth towards it, creating a second bulge and a second high tide

Question 13

What are neap tides

Answer 13

Twice a month, the moon and sun are perpendicular to each other, creating the lowest monthly tidal range

Question 14

What are spring tides

Answer 14

Twice a month, the moon sun and earth are in a straight line. The tide-raising force is strongest. Produces highest monthly tidal range.

Question 15

What is a sediment cell

Answer 15

A length of coastline and its associated nearshore area where the movement of coarse sediment is largely self-contained. Movement of sand and shingle shouldn’t affect beaches in a neighbouring sediment cell

Question 16

Characteristics of sediment cells

Answer 16

Function separately from each other
Geographically bound by significant disruptions
Sediment is the source, transfered, and stored. Coarse sediments are not exchanged, but finer sediment can be
Over time, sub-sinks will erode, and the sediment will re-enter the cell system

Question 17

What is the sediment budget

Answer 17

Amount if sediment available to the sediment cell. Will produce deposition features in equilibrium

Question 18

What can human interference do to processes in a sediment cell

Answer 18

Disrupt the supply of sediment and, therefore, the sediment budget of the cell

Question 19

What impact can groynes, jetties, and harbour walls have

Answer 19

They block the movement sediment, which can lead to beach erosion further down.
Groynes trap sediment in areas where a beach is considered essential.

Question 20

How can river dams and protecting soft cliffs affect sediment

Answer 20

River dams cut down on the amount of fluvial sediment entering the system.
Protecting soft cliffs can prevent cliff falls and reduce the amount of sediment entering the system

Question 21

What are the 4 sources of energy at the coast

Answer 21

Wind
Waves
Tides
Currents

Question 22

What makes stronger winds

Answer 22

Greater the pressure difference between two places (pressure gradient) the greater and faster the winds

Question 23

Where is the main source of energy derived from

Answer 23

From the sea in the form of waves

Question 24

What are the features of wind as an input into the coastal system

Answer 24

Prevailing wind direction
Fetch
Wave formation
Agent of erosion

Question 25

What is a fetch

Answer 25

The distance of open water over which wind blows uninterrupted by land obstacles. Length of the fetch determines the magnitude and energy of waves reaching the coast

Question 26

What is wave formation

Answer 26

Transfer of energy from the wind blowing over the sea surface. Energy acquired depends on the strength of the wind, time it's blowing and the fetch

Question 27

What is agent of erosion

Answer 27

Pick up and remove sediment from the coast and use it to erode other features. The most common type of wind erosion is abrasion. Moves sediment along the coast inland from the shoreline and beyond the tidal zone

Question 28

Nazare Portugal What causes the huge waves that attract tourists from all over the world

Answer 28

Long fetch Break very far from the coastline-friction Canyon Energy in the oceans Wind strength Storms cause pulses of energy, which creates swells and becomes waves Direction of the wind If the wind has travelled unbroken/uninterrupted Depth of the water Huge change in ocean depth

Question 29

What are longshore (littoral) currents

Answer 29

Most waves don't hit the coast head on but approach at an angle generating a flow of water running parallel to the shoreline. Moves water along the surf line and transports sediment parallel to the shoreline

Question 30

What are rip currents

Answer 30

Strong currents moving away from the shoreline. Develop when seawater is piles up along the coastline. Initially may run parallel before flowing out of the breaker zone.

Question 31

What is upwelling

Answer 31

Movement of cold water from deep in the ocean towards the surface. The denser colder water replaces the warmer surface water, creating nutrient rich cold ocean currents.

Question 32

What are the 3 main factors driving ocean currents

Answer 32

The rise and fall of tides Wind Thermohaline circulation

Question 33

Where are tidal currents strongest

Answer 33

Near the shore and in bays and estuaties

Question 34

How regular are tidal patterns

Answer 34

Very regular and can be predicted for future dates

Question 35

What do winds drive on a local and global scale

Answer 35

Local-currents causing upwelling currents Global-currents that circulate water for thousands of miles throught ocean basins(gyres)