Learn OC.6a Vocabulary

The time at which the tide reaches its highest level.

high tide

​The time at which the tide reaches its lowest level.

low tide

​The difference in height between consecutive high and low tides.

tidal range

​The time of greatest variation between high and low tides occurring when Earth, moon, and sun form a straight line.

​​spring tide

​The time of smallest variation between high and low tides, occurring when the Earth, moon, and sun align at right angles.

​​neap tide

​A “no-tide” point in the middle of a body of water from which tide crests rotate outward. Sometimes called a node. (Red dots in gif below.)

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​A tidal cycle of one high tide and one low tide per day.

diurnal tide

​A tidal cycle of two high tides and two low tides each lunar day, with the high tides of nearly equal height.

semidiurnal tide

A complex tidal cycle, usually with two high tides and two low tides of unequal height per day.

mixed tide

​The rise of fall in sea level causes water to flow in and out of bays and harbors.

​​tidal current

​Water rushing into an enclosed area as the tide is coming in.

​​flood current

​Water rushing out of an enclosed area as the tide is going out.

​​ebb current

​a.k.a. slack tide; time of no tidal currents and happens at high and low tides, when the current changes direction.

​​slack water