Which term describes a diurnal tide, characterized by one high tide and one low tide each day?

• A. Diurnal Tide
• B. Lunar Tide
• C. Equilibrium Theory of Tides
• D. Mean Sea Level

Answer: (A)

Tides come from the Moon and Sun pulling on the oceans as the Earth rotates. When a coast experiences two highs and two lows of about equal height each day, that pattern is called semidiurnal. If there is only one high tide and one low tide in a 24-hour period, the tide is diurnal. The diurnal pattern happens in places where coastline shape, ocean floor, and the Moon’s path combine so that one tidal bulge is favored by the coastline while the other is diminished. So the term for a diurnal tide is “diurnal tide.” The other terms aren’t describing this daily pattern: a “lunar tide” isn’t a standard term for a tide type, the “equilibrium theory of tides” is a model explaining how tides arise in a simplified sense, and “mean sea level” is a reference level, not a tidal pattern.