High tide usually lasts about 6 hours. And it’s generally the same for low tide. Also, tides hit a high and low usually twice a day.
But what causes tides? And why are there low and high tides?
The effects of the moon on ocean tides
The main reason that causes ocean tides is from the gravitational attraction between the moon and Earth:
- HIGH TIDE: When the moon is close to the Earth, it stretches the side of the planet that it’s facing. The side that is closest to the moon has a high tide because the moon pulls the body of water close to it.
- LOW TIDE: The side farthest away to the moon has a low tide because the gravitational force is weaker and doesn’t bulge out.
As the Earth rotates, the bulge shifts to the side facing the moon. But because oceans hold a set amount of water, water levels rise in one area and drop in another area. This is when there are high and low ocean tides.
Our enormous sun, which holds 99.9% of the total mass of the solar system, has an effect on the ocean tides as well. But it’s not as strong as the moon because the sun is farther in distance.
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- Oceanography: A Key to Better Understanding our World by the University of Barcelona
- Large Marine Ecosystems: Assessment and Management by the University of Cape Town and NOAA
- The Changing Arctic: Present, Past, & Future by the University of Colorado Boulder