When there is a low tide, the Moon faces the Earth at a right angle to the Sun so the gravitational force of the Moon and Sun work against each other. These tides are referred to as neap tides; a low tide or one that is lower than average.
A neap tide happens between two spring tides and occurs twice a month when the first and last quarter Moon appears. When there is a high tide, the Sun, Moon and Earth are in alignment and the gravitational force is strong.
It has a mass about 27,, times greater than the Moon. A very large object like the Sun would produce tremendous tides if it were as near to Earth as the Moon. When both the Sun and Moon are aligned, the effect of each is added together, producing higher than normal tides called spring tides.
Spring tides are tides with the greatest tidal range. They occur exactly halfway between the spring tides, when the Moon is at first or last quarter. The material that follows on tides was cut from Ocean Movements section under Coastal Processes. Tides are the daily rise and fall of sea level at any given place.
The Moon has a greater effect because, although it is much smaller than the Sun, it is much closer. High tide left and low tide right at Bay of Fundy on the Gulf of Maine. The Bay of Fundy has the greatest tidal ranges on Earth at To understand the tides it is easiest to start with the effect of the Moon on Earth.
As the Moon revolves around our planet, its gravity pulls Earth toward it. The lithosphere is unable to move much but the water is pulled by the gravity and a bulge is created.
This bulge is the high tide beneath the Moon. This creates a second high tide bulge on the opposite side of Earth from the Moon. Since so much water is pulled into the two high tides, low tides form between the two high tides Figure below. A spring tide is a common historical term that has nothing to do with the season of spring.
Rather, the term is derived from the concept of the tide "springing forth. Neap tides, which also occur twice a month, happen when the sun and moon are at right angles to each other. Tides are long-period waves that roll around the planet as the ocean is "pulled" back and forth by the gravitational pull of the moon and the sun as these bodies interact with the Earth in their monthly and yearly orbits.
During full or new moons—which occur when the Earth, sun, and moon are nearly in alignment—average tidal ranges are slightly larger. In 24 hours, the moon has moved enough so that it takes another 50 minutes for any specific point on Earth to catch up to the moon. The moon appears new dark when it is directly between Earth and the sun with the sun lighting up its backside , and full when Earth is between the moon and the sun.
In both these cases, the gravitational pull of the sun on Earth is added to the gravitational pull of the moon on Earth. The sun's pull is almost half as strong as the moon's, so working together, the oceans bulge even higher. In most places, the highest tides usually occur a day or two after new or full moon. This is because the tidal waves experience some friction in the ocean.
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