Which term refers to a tidal cycle with two high tides and two low tides per day, but with unequal heights between high tides?

• A. Mixed Tide
• B. Neap Tide
• C. Semidiurnal Tide
• D. Solar Tide

Answer: (A)

Two highs and two lows each day can occur in different forms, and the one described here is called a mixed tide. In a mixed tide, you still get two high tides and two low tides in a 24-hour period, but the heights of the highs (and sometimes the lows) are unequal. This unequal pattern arises from the way the sun’s and moon’s gravity interact with the shape and depth of the coastline and sea floor at a given location. Because the coastline and bathymetry modify how strongly each crest is elevated, one high tide can be noticeably higher than the other, even though the timing still follows roughly a semi-diurnal cycle. In contrast, a semidiurnal tide has two highs of about equal height, and neap tide relates to a reduced tidal range when the sun and moon are at right angles.