What is characteristic of mixed semi-diurnal tides?

• A. One high and one low tide per day
• B. Two high and two low tides of equal height
• C. Two high and two low tides that differ in height
• D. Constant tidal levels

Answer: (C)

Mixed semi-diurnal tides are characterized by having two high tides and two low tides each lunar day, with each high tide and low tide occurring at different heights. This variation results from the complex interplay of the gravitational influences of the moon and the sun, as well as local geographical features such as coastlines and bays.

In mixed semi-diurnal systems, the first high tide may be substantially different in height from the second high tide, and the same applies to the low tides. This contrasts sharply with diurnal tides, which have only one high and one low tide per day, and semi-diurnal tides, which have two high and two low tides of equal height. Thus, the option describing two high and two low tides that differ in height accurately reflects the nature of mixed semi-diurnal tides, making it the correct choice.