Ocean MotionOcean Motion

Part 1: WavesPart 1: Waves

Define wave:Define wave:

• Wave – a rhythmic movement that Wave – a rhythmic movement that carries energy through matter or carries energy through matter or space.space.– in the ocean, waves move through in the ocean, waves move through

seawater.seawater.

Parts of a waveParts of a wave

Crest Crest

Trough

Wavelength

Parts of a wave:Parts of a wave:

• CrestCrest – the highest part of a wave. – the highest part of a wave.

• TroughTrough – the lowest part of a wave. – the lowest part of a wave.

• WavelengthWavelength – the distance between – the distance between two adjacent crests.two adjacent crests.

• Wave heightWave height – the vertical distance – the vertical distance between the lowest part and the between the lowest part and the highest part.highest part.

Most waves caused by windMost waves caused by wind

• Friction from the wind moving over Friction from the wind moving over the water causes the water to move the water causes the water to move along with the wind.along with the wind.

• If the wind speed is high enough, the If the wind speed is high enough, the water begins to pile up and a wave is water begins to pile up and a wave is formed.formed.

How water moves in a How water moves in a wave:wave:

Particles of water move around in circles. The farther below the surface, the smaller the circle.

Waves move the water in a circular motion, and the energy travels across the water. At a depth about equal to half the wavelength, the motion stops.

EnergyEnergy

• Wind blown steadily over a great distance Wind blown steadily over a great distance will create a large amount of energy.will create a large amount of energy.

• Eg. northeast trade winds across the Eg. northeast trade winds across the Pacific Ocean near Hawaii or Westerlies Pacific Ocean near Hawaii or Westerlies across the Atlantic Oceanacross the Atlantic Ocean

• The energy can be harnessed as an The energy can be harnessed as an energy source.energy source.

At the beach:At the beach:• Wavelength decrease and wave height Wavelength decrease and wave height

increases as waves approach the shore.increases as waves approach the shore.

Constant

Wavelength

Waves drag against the bottom

and wave length decreases

At the beach, part 2At the beach, part 2• As the wave slows, its crest and trough come As the wave slows, its crest and trough come

closer together. The top of the wave is not closer together. The top of the wave is not slowed by friction and moves faster than the slowed by friction and moves faster than the bottom.bottom.

TidesTides•Caused by the gravitational pull of Caused by the gravitational pull of

the moonthe moon

•When the moon is directly When the moon is directly overhead, the water is pulled overhead, the water is pulled towards it.towards it.

•There is a similar bulge on the There is a similar bulge on the opposite side of the Earthopposite side of the Earth

•Low tides are at right anglesLow tides are at right angles

TidesTides

Types of TidesTypes of Tides• Spring Tides: Spring Tides:

– occur when the sun aligns with the occur when the sun aligns with the moon.moon.

– Happens about twice a monthHappens about twice a month– Tides are higher than normalTides are higher than normal

• Neap TideNeap Tide– the line of the sun and moon are the line of the sun and moon are

perpendicularperpendicular– The pulls works against each otherThe pulls works against each other– Tides are lower than normalTides are lower than normal

Timing of the TidesTiming of the Tides

• The tide cycle takes 12 hours and 25 The tide cycle takes 12 hours and 25 minutes minutes

• Eg. low tide at 7am, the evening low Eg. low tide at 7am, the evening low tide will be at 7:25pm.tide will be at 7:25pm.

• High tide occurs halfway throughHigh tide occurs halfway through– Approx. 1:12pmApprox. 1:12pm

• The tidal time moves forward about The tidal time moves forward about 50 minutes each day.50 minutes each day.