Ocean Waves and TidesOcean Waves and Tides

Wave – rhythmic movement that Wave – rhythmic movement that carries energy through matter or carries energy through matter or

spacespace

• Waves look like hills and valleys; the crest is the highest point and the trough is the lowest point.

• Wavelength is the horizontal distance between crests or troughs of two adjacent waves.

• Wave height is the vertical distance between crest and trough.

• As a wave passes, energy moves forward; the water molecules remain in about the same place.

• A breaker is a collapsing wave.

• Friction with the ocean bottom slows water at the bottom of the wave.

• Eventually the top of the wave outruns the bottom and it collapses.

• Wind forms waves as water piles up; wave height depends on wind speed, distance over which the wind blows, and the length of time the wind blows.

• The rise and fall in sea level, called a tide, is caused by a giant wave produced by the gravitational pull of the Sun and the Moon

• High tide – as the crest of this giant wave approaches shore, sea level appears to rise.

• Low tide – later, as the trough of the wave approaches, sea level appears to drop.

• The tidal range is the difference between the level of the ocean at high tide and low tide.

• Tidal range can vary; most shorelines have tidal ranges between 1 and 2 m

• Some have tidal ranges of only about 30 cm

• Other places have tidal ranges as high as 15 m

• When a rising tide enters a shallow, narrow river from a wide area of the sea, a wave called a tidal bore forms.

• Tides are caused by the interactions of gravity in the Earth-Moon system.

• When the Sun, Earth, and the Moon line up in certain ways, the Sun can strengthen or weaken the Moon’s effects.

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• Springtides – higher high tides and lower low tides

• Neap tides – lower high tides and higher low tides