Which term describes small tidal range at quarter moons?

• A. Slack water
• B. Spring tide
• C. Tidal bore
• D. Neap tide

Answer: (D)

At quarter moons, the Moon is positioned so that the Sun’s gravity and the Moon’s gravity act at right angles on Earth’s oceans. This perpendicular alignment causes the Sun’s pull to partly offset the Moon’s pull, so the difference between high and low tides is smaller. That reduced range is what we call a neap tide. In contrast, when the Sun and Moon align during full or new moons, their forces reinforce each other and produce a larger tidal range (spring tides). Slack water is just the lull between tides, and a tidal bore is a large wave moving upriver—neither describes the smaller tide range at quarter moons.