What kind of tide can occur at the first and third quarter moon?

• A. Neap
• B. High Tide
• C. Low Tide
• D. Spring Tide

Answer: (A)

Tides come from the Moon’s gravity pulling on Earth’s oceans, with the Sun’s gravity also tugging on those oceans. When the Moon is at the first and third quarter phases, it sits at right angles to the Sun as seen from Earth. In this setup, the gravitational forces from the Moon and Sun pull in roughly perpendicular directions, so they don’t combine to create large bulges. The result is a smaller difference between high and low tide—the tidal range is reduced. This is what sailors call a neap tide: lower high tides and higher low tides compared with spring tides. During new or full moon, the Sun and Moon align and their gravities reinforce each other, producing spring tides with larger tidal amplitudes.