Waves are energy moving across the ocean

1. 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 CharacteristicsWavelength

Crest

Still-water line

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– 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)