Water has a much easier time moving around, and the water wants to bulge in the direction of the moon. This is called the tidal force. Because of the tidal force, the water on the side of the moon always wants to bulge out toward the moon. This bulge is what we call a high tide. As your part of the Earth rotates into this bulge of water, you might experience a high tide. An illustration of the tidal force, viewed from Earth's North Pole. Water bulges toward the moon because of gravitational pull.
Note: The moon is not actually this close to Earth. One thing to note, however, is that this is just an explanation of the tidal force—not the actual tides. In real life, the Earth isn't a global ocean, covered in an even layer of water. There are seven continents, and that land gets in the way.
The continents prevent the water from perfectly following the moon's pull. That's why in some places, the difference between high and low tide isn't very big, and in other places, the difference is drastic. The tidal force causes water to bulge toward the moon and on the side opposite the moon.
These bulges represent high tides. 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. This occurs twice each month. The moon appears new dark when it is directly between the Earth and the sun. The flow and ebb are gradual, so it is not accurate to say that a high or low tide lasts around 6 hours and 12 minutes, i.
The speed of the water flow varies during this period, and it also varies from place to place. People who have to consider the tides in their daily life, like sailors, fishers, and surfers, often use what is called the rule of 12ths to calculate the expected water level.
In the 1st hour, the tide would rise 1 foot. In the 2nd hour, it would rise 2 feet. In the 3rd and 4th hours, it would rise 3 feet. In the 5th hour, the tide would rise 2 feet, and in the 6th hour, 1 foot. The astronomical forces that drive the tides can be predicted very accurately, and these predictions are published in local tidal tables.
However, different weather conditions also affect the sea level and may cause both lower and higher tides than expected. If there is a storm, the seawater level often increases. This is called a storm tide and is caused by a combination of storm surge and normal tidal movement. Strong offshore winds can move water away from coastlines, exaggerating the low tide. At the same time, onshore winds may cause the water to pile up onto the shoreline, making the low tide higher than usual.
High-pressure weather systems can lead to days with exceptionally low tides. In contrast, low-pressure systems may contribute to causing much higher tides than predicted.
The average tidal range in mid-ocean is around 1 meter or 3 feet. However, in some coastal areas, the tidal range can be more than 10 times higher in the most extreme regions. To give an average for tidal range along the world's coastlines doesn't make much sense, as they vary so much from place to place. The world's highest tide is in the Bay of Fundy in Canada, where the difference between low and high tide can be up to Those high highs and low lows are about the same at both the full and the new moon when the moon is dark.
The next new moon is Sept. Now, how about those supermoons that caused a buzz — and some spectacular photography — all summer? Shipman said they also have an influence on tides, more even that a traditional full or new moon: "A supermoon happens when the moon is near the closest point in its orbit. The moon only comes a few percent closer at some points in its elliptical orbit around the earth.
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