Waves and Tides

Wave CharacteristicsMost ocean waves are energy passing through

water caused by the windCrests are the top of the wavesTroughs are the bottom of the waves

Pair Share: How do the water molecules move in a wave?

Answer: in a circle

Wave CharacteristicsWave Height is the vertical distance between

trough and crestWavelength is the horizontal distance between

two crests or two troughsWave period is the time one wave takes to pass a

fixed position. Pair Share: How many wavelengths will snowball surf?

Answer: 2

Factors affecting WavesThe height, length, and

period of a wave depends of three factors:Wind speedLength of time the wind

has blownFetch, or the distance that

the wind has traveled across open water

Wave MotionWaves can travel great distances across ocean basinsThe energy of the wave, not the water itself, travels

across the oceanCircular orbital motion allows energy to move through

the water, water particles move in circlesEnergy is moved across the ocean as well as downward

Breaking WavesIn deep water waves are

unaffected by depthIn shallow water wave

speed slows down causing waves farther out to catch up

Speed decrease, wavelength shortens, the wave grows higher

When wave is too high to support itself, it collapses

Turbulent water created by breaking waves is called surf

Tides

Tides are regular changes in the elevation of the ocean surface

The pull of gravity from the moon and, to a lesser extent by the sun, creates tides

Pair Share: Which picture shows high tide?

Answer: the bottom one

What Causes TidesThe difference in the gravitational pull of the moon on the

near and far side of the Earth stretches the EarthInertia is the property of an object that is in motion to stay

in motion, and an object at rest to stay at rest.Due to inertia ocean water flows towards both areas -

closest and farthest from the moon - creating a tidal bulge

Pair Share: What causes the high tides on both sides of the Earth?

Answer: Inertia!

Tidal CycleSpring tides are when the

sun and moon are aligned, their forces of gravity creates larger tidal bulges

Spring tides happen during new and full moons.

Neap tides are when the sun and moon are not aligned, their forces off-set each other, creating small tidal bulges

Pair Share: Do Spring tides happen only in the Spring?

Answer: No they happen twice every month.

Tidal PatternsTidal Patterns

Many factors effect tides, such as shape of the Many factors effect tides, such as shape of the coastline, the ocean basins, and water depthcoastline, the ocean basins, and water depth

Three main tidal patters:Three main tidal patters:Diurnal tidesDiurnal tides – single high tide and single low – single high tide and single low

tide each tidal daytide each tidal daySemidiurnal tideSemidiurnal tide – two high tides and two low – two high tides and two low

tides each tidal daytides each tidal dayMixed tideMixed tide – Usually two high and two low tides, – Usually two high and two low tides,

however heights are varied. (Our tides here on the however heights are varied. (Our tides here on the Pacific Coast)Pacific Coast)

WHITE BOARD REVIEW

1. What is a wave period?2. How does energy move

through a wave?3. What causes tides?