How long high tides last

Solar day: In a solar day, it takes the earth 24 hours to orbit around the sun. Lunar day: Unlike a solar day, a lunar day takes 24 hours and 50 minutes to make its full rotation of its axis. This is longer because the moon revolves around the earth in the same direction as the earth rotates on its axis. A common misconception about tides is that the ocean only moves in one direction, towards the side of the earth that is closest to the moon.

If this was the case there would only be one high tide and one low tide in each 24 hour 50 minute period. In reality, the part of the earth that is both closest to the moon and furthermost away from the moon will receive high tides within a 24 hour 50 minutes period, whilst other areas of the earth will then see a low tide. This is because water is being pulled towards the moon on one side of the earth and the earth pulled away from the water on the other side of the earth, creating a bulging effect and a high tide at opposite sides of the earth.

A high tide is when the ocean is at its fullest point on the beach. A high tide is caused when the moon is overhead or at its closest to the earth and when it is at its furthermost away. A low tide is caused when the ocean is at its lowest point of the beach.

On the beach, we notice that the sea is far away and leaves a large patch of sand once covered at high tide exposed. Low tides are caused when the earth is a right angles to the moon. As well as having high tides and low tides each day we see a variation in the size of these high tides and low tides.

This again is due to the rotation of the earth and each phase of the lunar cycle that we pass dictates the size of the tides. A spring tide or king tide can be defined as high high tides and low low tides or large tidal movement between one tide and the next. If you are surfing or at the beach during this phase of the lunar cycle you will notice a big difference between low tide and high tide. When the sun and the moon are aligned both on the same side of the earth that makes the gravitation pull very strong creating high high tides and low low tides.

The tidal range is smaller than of a Spring tide. This occurs twice every month when the sun and the moon are at right angles to each other the solar tide partially cancels out the lunar tide making for a small tidal range.

The tide will affect the surf in a variety of ways. Waves are formed as the energy or swell in the ocean moves from deep water to shallow water and is forced upwards, waves will then peak and start to break as the hit sand banks or reef that make up the bathymetry of the sea floor.

The volume of water that covers these sandbanks or reefs will effect how quickly the waves form and break. Waves at high tide are said to be fat and slow ,or lumpy due to the large amount or volume of water that is sitting over the sand banks or reef on that particular beach.

Waves at low tide are said to be quick, steep or dumpy, this is because there is very little water sitting over the sand bank or reef allowing the ocean swells to travel from very deep water straight into very shallow water.

Every beach is different: All beaches have a different topography which causes the waves to form and break. On the side of Earth farthest from the moon, the moon's gravitational pull is at its weakest.

At the center of Earth is approximately the average of the moon's gravitational pull on the whole planet. Arrows represent the force of the moon's gravitational pull on Earth.

To get the tidal force—the force that causes the tides—we subtract this average gravitational pull on Earth from the gravitational pull at each location on Earth. The result of the tidal force is a stretching and squashing of Earth. This is what causes the two tidal bulges. Arrows represent the tidal force. It's what's left over after removing the moon's average gravitational pull on the whole planet from the moon's specific gravitational pull at each location on Earth.

These two bulges explain why in one day there are two high tides and two low tides, as the Earth's surface rotates through each of the bulges once a day. The Sun causes tides just like the moon does, although they are somewhat smaller.

When the earth, moon, and Sun line up—which happens at times of full moon or new moon—the lunar and solar tides reinforce each other, leading to more extreme tides, called spring tides. When lunar and solar tides act against each other, the result is unusually small tides, called neap tides. There is a new moon or a full moon about every two weeks, so that's how often we see large spring tides. When the gravitational pull of the Sun and moon are combined, you get more extreme high and low tides.

This explains high and low tides that happen about every two weeks. Note: this figure is not to scale. The Sun is much bigger and farther away. Wind and weather patterns also can affect water level. Strong offshore winds can move water away from coastlines, exaggerating low tides. Onshore winds can push water onto the shore, making low tides much less noticeable.

High-pressure weather systems can push down sea levels, leading to lower tides. The bulge on the far side of the Earth is caused by inertia. The water moving away from the moon resists the gravitational forces that attempt to pull it in the opposite direction.

Because the gravitational pull of the moon is weaker on the far side of the Earth, inertia wins, the ocean bulges out and high tide occurs. As the Earth spins, different areas of the planet face the moon, and this rotation causes the tides to cycle around the planet.

NOS scientists advanced tidal recording systems as well as satellite imagery to monitor tides and water levels. These data are used to predict ocean behavior in order to protect our coasts and coastal communities. Home Ocean Facts How frequent are tides?