During which phase of the moon do spring tides occur most strongly?

Spring tides occur most strongly during the full moon phase, as well as during the new moon phase. This happens due to the alignment of the Earth, moon, and sun, which leads to the gravitational forces of the moon and the sun combining to produce higher high tides and lower low tides.

During a full moon, the sun and moon are on opposite sides of the Earth, both exerting gravitational pull in the same direction on the oceans, which leads to particularly high tides. Similarly, during the new moon, the sun and moon are aligned with the Earth, again resulting in heightened tides.

The first and last quarter phases of the moon do not produce spring tides, as during these times the sun and moon are at right angles relative to the Earth. This results in lower tidal ranges, known as neap tides, where high tides are not as high, and low tides are not as low compared to spring tides.

So, while both the full moon and new moon are associated with spring tides, the full moon is specifically noted for the substantial intensity of those tides.