How does the tidal range change from neap to spring tide and from spring to neap tides?
Spring tides are when the range from high tide to low tide (about a six hour period) is most different. This effect is caused by the sun and moon being either on the same side of Earth (during new moon phase), or on opposite sides of Earth (during full moon phase), thus creating an additive effect of the Lunar gravity and Solar gravity. Neap tides occur during the 1st and last quarter moon phases when the Sun and Moon are at right angles to Earth, so the gravity of the sun pulls one way while the moon pulls 90 degrees to the sun, somewhat canceling each other’s effect. So the range from high to low tide is not very great.
