Which tidal pattern has two high tides and two low tides each lunar day, with the highs nearly equal in height?

Which tidal pattern has two high tides and two low tides each lunar day, with the highs nearly equal in height?

• A. Mixed Tide
• B. Neap Tide
• C. Semidiurnal Tide
• D. Tidal Bore

Answer: (C)

The main idea is semidiurnal tides. When the Moon’s gravity and the Sun’s gravity pull on Earth in roughly the same alignment, two tidal bulges form on opposite sides of the planet. As a coastline moves through these bulges, you get two high tides and two low tides each lunar day. The highs are nearly the same height because the solar and lunar tides reinforce each other in a balanced way on open coasts. Neap tides occur when the Sun and Moon are at right angles, reducing high tides; a mixed tide has highs of unequal height; a tidal bore is a surge moving upstream in a river, not regular semidiurnal tides.

The main idea is semidiurnal tides. When the Moon’s gravity and the Sun’s gravity pull on Earth in roughly the same alignment, two tidal bulges form on opposite sides of the planet. As a coastline moves through these bulges, you get two high tides and two low tides each lunar day. The highs are nearly the same height because the solar and lunar tides reinforce each other in a balanced way on open coasts. Neap tides occur when the Sun and Moon are at right angles, reducing high tides; a mixed tide has highs of unequal height; a tidal bore is a surge moving upstream in a river, not regular semidiurnal tides.