How it works
A blank ocean wave diagram to label by hand. Two side-on drawings, with the waves moving to the right: one wave in deep water with seven parts to name, and the same waves reaching a beach with five.
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Seven names on the wave at sea
Two ringed dots sit on the water: the high one is the crest and the low one the trough. Two spans are measures: the level one above the water is wavelength, the upright one wave height. The column of shrinking circles is orbital motion, and the long-dashed line under it is the wave base. The wide arrow is direction of travel.
Five names at the beach
Work from the open sea toward the sand. Swell is the low, even waves farthest out, the breaker is the tall wave with a curling top, and the surf zone the foamy water after it. Of the two arrows over the sand, the one pointing up the beach is swash and the one pointing back down is backwash.
- Word bank: backwash, breaker, crest, direction of travel, orbital motion, surf zone, swash, swell, trough, wave base, wave height, wavelength.
Questions and answers
What is the still water level of a wave?
Where the surface of the sea would be if there were no waves and the water was completely calm. On the sheet it is the short-dashed line through the waves. It has no line to write on: it is drawn and not asked.
How deep is the wave base?
About half a wavelength down. Most ocean waves are less than a few hundred meters from crest to crest, so most of the deep ocean is never stirred by the waves on its surface.
What are the three types of breaking waves?
Spilling, plunging and surging. Spilling breakers form on gently sloping beaches, plunging breakers on steeper shores, where the crest outruns the wave and curls forward, and surging breakers on the steepest shorelines. The breaker on the sheet curls, so it is a plunging one.
What is the difference between swell and wind waves?
Wind waves are made near the wind that raises them. Swell is waves that have outrun their storm: lower, longer and regular, able to travel thousands of miles. The sheet draws swell as the low, even waves farthest from the beach.