Neap and Spring Tides

Neap and Spring Tides The sun, because of its greater distance from the earth, though much larger in size than the moon, has a tide-producing power that is only five­elevenths the tide-producing power of the moon. When the earth, the moon and the sun are in a straight line,' the gravitational force is at its greatest because tide-producing forces of both sun and moon complement each other and they 'pull' together. This produces tides of unusually great range, called the spring tides. These occur about twice a month: at new moon when the sun and the moon are in conjunction, and at full moon when they are in opposition.

When the earth, the moon and the sun are not in a straight line, but are at right angles to the earth, the gravitational force is less as the sun and the moon are not pulling together. This happens during phases of first and third quarter, Le., at half moon, the sun's tide-producing force tends to balance the tige-producing force of the moon, resulting in tides of unusually small range known as neap
tide? Amplitude or tidal range refers to the difference' between high tide and low tide; it is high at spring tides and low at neap tides.