Tides

Diurnal Tides

One high tide and one low tide per lunar day, typical of some Gulf of Mexico and Southeast Asia locations.

Semidiurnal Tides

Two high tides and two low tides of approximately equal height per lunar day, common along eastern coasts of North America and Western Europe.

Mixed Tides

Two high tides and two low tides per lunar day, but heights of successive high tides and low tides differ, often occurs along Pacific coasts.

Spring Tides

Tides with the largest tidal range, occurring during full moon and new moon when the sun, moon, and Earth are aligned.

Neap Tides

Tides with the smallest tidal range, occurring during the first and third quarter moons when the sun and moon are at right angles to each other.

Tidal Resonance

Occurs when the natural period of oscillation of a body of water matches the period of the incoming tidal forcing, amplifying tidal ranges.

Flood Current

Water moves toward the shore as the tide rises, strongest at mid-tide in many locations.

Ebb Current

Water moves away from the shore as the tide falls, often stronger than flood in certain estuaries.

Slack Water

Period when water stops moving between flood and ebb, occurring at high tide and low tide.

Velocity of Tidal Currents

Varies with tidal range, basin shape, and friction.

Navigation Effects of Tides

Strong tidal currents affect ship movement and port operations.

Erosion and Sediment Transport

Tides move sand and silt, shaping estuaries, tidal flats, and deltas.

Ecological Role of Tides

Tidal currents distribute nutrients and oxygen in intertidal zones and estuaries.

Energy Potential from Tides

Tidal currents can be harnessed for tidal stream power.

Characteristics of Mixed Tides

Differing heights of high and low tides, with one high tide higher than the other and one low tide lower than the other.