Tides And Currents Flashcards
(34 cards)
What are tides?
The periodic rise and fall of sea levels caused by the gravitational pull of the moon and the sun.
Tides are influenced by the positions of the moon and the sun relative to Earth.
Define tidal range.
The difference in height between high tide and low tide.
A larger tidal range results in more significant wave energy variations.
What are spring tides?
Occur during the full moon and new moon phases when the sun, moon, and Earth are aligned, resulting in higher high tides and lower low tides.
These tides are characterized by a greater tidal range.
What are neap tides?
Occur during the first and third quarters of the moon when the sun and moon are at right angles to each other, leading to lower high tides and higher low tides.
Neap tides have a smaller tidal range.
What are tidal currents?
The horizontal flow of water associated with the rise and fall of the tide.
Tidal currents can transport sediment and shape coastal features.
Define rip currents.
Powerful, fast-moving currents that pull water away from the shore, caused by waves breaking on the shore and creating a buildup of water.
Rip currents often occur through narrow, concentrated channels.
What generates waves in the sea?
Waves are generated by wind blowing over the surface of the sea
What is the crest of a wave?
The point at the top of a wave
What is the trough of a wave?
The base of a wave
What is wave height?
Distance between the trough and the crest
What is wave length?
Distance between two wave crests
What does wave frequency refer to?
How often the waves break per minute
Define swash in terms of wave action.
Waves running up the beach
Define backwash in terms of wave action.
Waves returning to the sea due to gravity
What are constructive waves?
Waves that build up beaches by depositing sediment
List characteristics of constructive waves.
- Weak backwash compared to swash
- Long wavelength, low wave height
- Less frequent gentle waves (6-9 waves per minute)
- Break gently, spread out over a wide area
- Found in sheltered bays, build up sandy beaches
- More common in summer than winter
- Adds material to the beach
What are destructive waves?
Waves that erode the coastline by removing sediment
List characteristics of destructive waves.
- Strong backwash compared to swash
- Short wavelength, high wave height
- Frequent waves (10-15 waves per minute)
- Break with a lot of energy, concentrated in a small area
- Found in more exposed areas of coastline
- More common in winter than summer
- Removes material from the beach
What is fetch in the context of wave energy?
The distance over which the wind blows
How does wind strength influence wave energy?
Stronger winds generate larger, more energetic waves
What effect does wind duration have on wave energy?
The longer the wind blows, the more energy is transferred to the waves
What is hydraulic action?
The force of water hitting the coast, compressing air in cracks and causing rock to break apart
Define abrasion in coastal erosion.
Waves carrying sediment grind against the coast, wearing it down
