Unit 8: Waves and tides Flashcards
What is a wave
A cycle that travels through the water, transferring energy through its motion.
Waves are generated by:
Wind, seismic, or volcanic activity, and gravitational attractions (tides)
Wind waves:
Formed by the transfer of energy from wind to water.
Friction force of wind on surface water forms ripples, or capillary waves
These capillary waves deflect and slow surface wind, causing some of the wind’s energy to be transferred to the water, driving the wave forward.
3 Factors to wind growth:
Wind strength
Wind duration
Fetch
Wind strength:
Wind must move faster than the wave crests for energy to be transferred from the air to the sea.
Wind duration:
High winds that blow for only short times can’t generate large waves.
Wind duration:
High winds that blow for only short times can’t generate large waves.
Fetch:
Distance over which wind blows
4 Factors that affect speed and direction of wind:
1) Wave refractions - Slowing down or speeding up and bending of waves as they enter different depths.
2) Wave difraction - Disturbance of a wave as a result of an obstacle
3) Wave reflection - When waves bounce back from an obstacle
4) Wave interference - Overlapping of waves can lead to the cancelling or an increase in amplitude of waves.
Tides:
The regular rising and falling of sea levels caused by the:
- Rotation of the Earth
- The gravitational pull of the Sun and Moon
Effects of Sun on Tide:
When sun and moon are at a 90 degree angle to each other, and 1/4 and 3/4 moon, their gravitational pulls on the oceans are also at 90 degree angles, pulling the ocean two ways. This flattens out bulge created by moon, creating a low high tide (reap tide) and a high low tide.
When they are in line, they combine forces to form the highest high tide (spring tide) and the lowest low tide.
