Module 11 - Tides & Tidal Streams
Springs and Neaps
When the Sun and Moon align (new moon and full moon), their gravitational pulls combine, producing spring tides — the highest highs and lowest lows. When the Sun and Moon are at right angles (first and third quarter), their pulls partially cancel, producing neap tides — smaller range between high and low.
The spring/neap cycle takes about 14 days (half a lunar month). Spring tides occur a day or two after the new and full moons. Tidal range at springs can be double or more compared to neaps. Equinoctial springs (near the equinoxes in March and September) tend to produce the largest ranges of the year.
Key points
- Spring tides — Sun and Moon aligned (new/full moon). Largest range.
- Neap tides — Sun and Moon at 90° (quarter moon). Smallest range.
- Spring/neap cycle ≈ 14 days
- Springs occur 1–2 days AFTER new/full moon
- Equinoctial springs (March/September) are the biggest of the year
Tip: Spring tides are NOT related to the season of spring. They 'spring' up to their highest.
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