Section 4: Ocean Waves & Tides

A wave starts in the open ocean and is the movement of energy through a body of water. A wave is usually formed when winds blow across the water’s surface, which transfers energy.  The crest is the highest point of a wave, whereas the trough is the lowest point.  The wavelength is the measure of the distance from one crest to another or one trough to another.  The amplitude is the amount of energy a wave carries that is measured from resting point to crest.  The frequency is the number of waves that pass a point in a certain amount of time.

Tides are the daily rise and fall of Earth’s water on its coastlines. Tides are caused by the gravitational interaction of Earth, the moon, and the sun.  These gravitational forces produce two bulges on ocean surfaces.  There is one bulge on the side of the Earth that faces the moon, and the other bulge is on the side that’s facing away from the moon.  These bulges represent high tides.  The tidal range is the difference in water level between a high tide and a low tide.  It varies depending on the positions of the sun and the moon with respect to Earth.  A spring tide is the largest tidal range, and it occurs when Earth, the moon, and the sun form a straight line.  A neap tide is the lowest tidal range, which occurs when Earth, the moon, and the sun form a right angle.








  1. Identify the main parts of a wave.
  2. What are tides?
  3. Compare a spring tide to a neap tide.

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