Tide FAQ: Top Questions About Ocean Tides

1. What causes tides?

Tides are caused by the gravitational pull of the Moon and Sun on Earth’s oceans, combined with the rotation of Earth.

2. Why are there usually two high and two low tides each day?

Earth’s rotation and the Moon’s gravitational field create two tidal bulges—one facing the Moon and one on the opposite side—resulting in two high tides and two low tides daily (semi-diurnal tides).

3. What is the difference between spring and neap tides?

Spring tides are stronger tides that occur when the Sun, Moon, and Earth are aligned (new and full moons). Neap tides are weaker and occur when the Sun and Moon are at right angles (quarter moons).

4. Does the Sun affect the tides?

Yes. Though it exerts less gravitational force than the Moon due to distance, the Sun still contributes to tidal variation, especially during spring and neap tides.

5. Why are tide heights different in different places?

Local geography, ocean basin shape, water depth, coastline configuration, and Earth’s tilt all influence the amplitude and timing of tides.

6. What are amphidromic points?

Amphidromic points are areas in the ocean where there is almost no tidal variation. Tidal waves rotate around these points in a circular pattern due to Coriolis forces and basin geometry.

7. What is a tidal range?

Tidal range is the vertical difference between high tide and the subsequent low tide. It varies daily and seasonally based on lunar position and local conditions.

8. Are tides the same every day?

No. Tides follow a ~24.8-hour cycle (a lunar day), not a 24-hour solar day. Therefore, each high or low tide occurs roughly 50 minutes later each day.

9. How accurate are tide predictions?

Very accurate in the short term, because they’re based on astronomical cycles. However, wind, atmospheric pressure, and storm surge can cause deviations in real-time water levels.

10. Do tides affect marine life?

Yes. Many species synchronize feeding, spawning, and migration with tidal cycles. Intertidal zones also depend on tides to regulate habitat exposure.