Coasts (KQ1) Flashcards
(45 cards)
1
Q
What is the coastal area made up of?
A
- offshore
- nearshore
- foreshore
- backshore
2
Q
What different coastal environments are there?
A
- cliffed
- sandy
- muddy
- rocky
3
Q
What factors affect coastal environments?
A
- geology
- waves
- ecosystems
- tides
- currents
- human activities
(remember GWETCH)
4
Q
How do waves develop?
A
- waves develop when energy from wind blowing across seas and oceans are transferred to the water surface
5
Q
What is wave movement affected by?
A
- wind direction
6
Q
How do waves crash onto the shore?
A
- onshore winds push waves towards the coast
- this results in waves crashing onto the shore
7
Q
What is wave length?
A
- horizontal distance from crest to crest
- or trough to trough
8
Q
What is wave frequency?
A
- number of wave crests or troughs that pass a fixed point in one second
9
Q
What is wave height?
A
- vertical distance between the crest and trough
10
Q
What is a crest?
A
- highest part of the wave
11
Q
What is a trough?
A
- lowest part of the wave
12
Q
How do water particles move?
A
- in an orbit
- decreases with depth
13
Q
What factors affect wave energy?
A
- wind speed
- wind duration
- fetch
14
Q
What is fetch?
A
- distance that wind has travelled over seas and oceans to form waves
15
Q
How does wind speed affect wave energy?
A
- the faster the wind blows, the greater the wave energy
16
Q
How does wind duration affect wave energy?
A
- the longer the wind blows, the larger the waves
- results in greater wave energy
17
Q
How does fetch affect wave energy?
A
- the greater the fetch, the more energy waves have
18
Q
How can the amount of energy present in a wave be told?
A
- wave steepness
- wave period
19
Q
What is wave steepness?
A
- ratio of wave height to wave length
20
Q
What is wave period?
A
- the time waves take to travel through one wave length
21
Q
What is the relationship between wave energy and wave steepness as well as wave period?
A
- the higher the wave energy, the steeper the wave and the shorter the wave period
22
Q
What do waves in the open ocean have?
A
- long wave length
- low wave energy
23
Q
What happens to waves near the coastline?
A
- water is shallow
- waves interact with sea bed
- waves start to change shape at a depth equivalent to about half their wave length
24
Q
What happens to waves nearer the coastline?
A
- base of the wave starts slowing down due to friction
- thus, wave height increases and wave length decreases
25
What happens to waves nearest the coastline?
- base of the wave stops but wave crest becomes steeper and topples over
- causes wave to break onto coast
- releases energy of the wave
- surfers ride on these
26
What is the difference between backwash and swash?
- backwash carries sediments from the shore into the sea
- swash carries sediments onto the shore
27
What are the two types of waves?
- constructive
- destructive
28
What do constructive waves do?
- strong swash, weak backwash
- strong swash deposits materials on the coast
- weak backwash only removes some materials
- landforms on beaches are 'constructed' by strong swash and weak backwash
29
What do destructive waves do?
- weak swash, strong backwash
- instead of depositing sediments onto the coast, destructive eaves erode coasts and transport rocks and beach materials away
30
What are some differences between destructive and constructive waves?
- constructive waves break on low gradient, low energy environments while destructive waves break on steep gradient, high energy environments
- constructive waves are small and low while destructive waves are large and high
- constructive waves have low wave height and long wave length while destructive waves have high wave height and short wave length
- constructive waves have a lower wave frequency than destructive waves (6-8/minute vs 10-14/minute)
- constructive waves have stronger swash and weaker backwash while destructive waves have weaker swash and stronger backwash
- constructive waves occur on gentle coastal slopes and sheltered coasts and destructive waves occur on steep coastal slopes and open coasts
- the deposition process is more prominent in constructive waves while the erosion process is more prominent in destructive waves
31
What is wave refraction?
- the process by which waves change direction as they approach the coast
- this occurs as waves slow down due to interaction with the sea bed as they move towards the coast
32
What is the process of wave refraction?
- waves approach the headland and bend towards it
- thus, more erosion will occur due to the wave energy being concentrated there
- waves diverge when they reach the adjacent bays
- more deposition will occur in bays where wave energy is spread out
33
What are the different coastal processes present?
- coastal erosion
- sediment transportation
- sediment deposition
34
What are the 4 ways in which coastal erosion happens?
- hydraulic action
- abrasion
- attrition
- solution
35
How does hydraulic action happen?
- when waves strike against a rock surface, the waves trap air in the rock joints
- the air is compressed by the oncoming waves
- this exerts pressure on the joints
- as air is repeatedly compressed, joints weaken and rocks shatter
36
How does abrasion happen?
- as waves break, sediments carried by waves such as sand and rocks are hurled against the coast
- the loosened sediments knock and scrape against the coastal cliffs
- this weakens the surface and breaks down the coast
- over time, the impact from abrasion undercuts a cliff
37
How does attrition happen?
- when rock particles carried by waves rub or hit against one another
- they break down into smaller pieces and become smoother and more rounded
38
How does solution happen?
- sea water chemically reacts with water soluble minerals in coastal rocks and dissloves them
- for example, limestone rocks are easily eroded by carbonic acid
- when solution of minerals occurs, rocks are weakened and disintigrate
39
How are sediments transported along coasts?
- beach drift
- longshore drift
40
What is beach drift the result of?
- waves approaching the coast at an oblique angle
- as waves approaching the coast at an oblique angle break on the beach, sediments move up the beach at an angle as swash and move perpendicularly down as backwash
- the zigzag movement along the beach is known as beach drift
41
How are longshore currents generated?
- when waves approach the coast at an oblique angle, they generate longshore currents in the nearshore zone
- they move sediments along the shore
42
What are longshore currents?
- ocean currents that flow parallel to the coast
43
What is longshore drift made up of?
- combined effect of sediment movement by longshore currents and beach drift
44
When is longshore drift the most rapid?
- when waves approach a straight coast at an angle of about 30 degrees
45
How are the landforms present on cliffed coasts?
- cliffs
- shore platform
- headland
- bay
- cave
- arch
- stacks
