WAVES

Waves are energy moving across the ocean Waves can be caused by 3 things: A. Wind (Wind-driven waves) B. Moon’s and Sun’s gravitational attraction (Tides) C. Earthquakes, volcanic eruptions, landslides, meteorites (Tsunami’s / Seismic Waves)

Wind-Driven Waves 2. The size of a wind driven wave is determined by: a. time the wind blows b. the speed of the wind c. Fetch – distance over water that the wind blows

Characteristics of waves 3. Characteristics of waves include: a. Crest – the highest point of a wave b. Trough – the lowest point of the wave c. Wavelength (λ) – Distance between successive (2) crests or successive (2) troughs d. wave height- distance between a crest and a trough

e. Still water line – level of the water if there was no wind f. Amplitude – ½ the wave height; the distance between the crest or the trough and the still water line g. Frequency – the number of waves that pass a particular point in a given time period (waves/sec) h. Period – the time it takes for two successive waves to pass a particular point (sec/wave) i. Speed – wavelength/period

Wave Characteristics Still-water line Wavelength Crest Wave height Trough Amplitude

Types of Water Waves Wind-driven (capillary) wave – small ripples less than 1” tall, restoring force is surface tension Wind-driven (gravity) wave – waves greater than 1” tall, restoring force is gravity Seismic wave (tsunami) – caused by earthquakes, volcanic eruptions, landslides, and meteorites. Restoring force is gravity. Deep water – long wavelength and short amplitude A boat at sea may not even notice the tsunami underneath Shallow water – short wavelength and high amplitude Wave height increases dramatically depending on shoreline topography

Tides – extremely long wavelength, caused by gravitational attraction between earth, moon, and sun and centrifugal force (due to Earth’s rotation). Restoring force is gravity and Coriolis effect.

Wave Interaction Constructive interference Destructive interference Occurs when the crest of waves coming from two directions coincide and the resulting wave crest is higher than either one was Maybe an explanation for rogue waves Destructive interference Occurs when the crest and troughs from two waves coincide and the resulting wave is basically cancelled out.

Orbital Wave Motion Deep water wave – water particles move in a circular orbit and the size of the orbit decreases with depth Little to no water movement at a depth greater than ½ the wavelength.

Shallow water wave – orbitals become flattened as water becomes shallow and the wave “feels” bottom When water depth is less than ½ the wavelength the top of the wave moves forward faster than the bottom of the wave and it “breaks”

Types of Breakers Spilling breakers – water from the top of the wave spills or tumbles down the front of the wave Most waves on Miami Beach are this type Found when shorelines are gently sloped

Plunging breakers – is formed when the wave crest curls over an air pocket and collapses Type preferred by surfers in Hawaii and California Found in areas where the shoreline is steeply sloped

Surging breakers – formed when the shoreline is more like a wall that rises out of the water and so the wave is not slowed down but surges into shore can be very destructive