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Why Tides?

Many people new to the coastal region have never experienced tides, while those who live on the coast live according to the never-ending beat of the rise and fall of the water. So whether you’re an old salt or an land lubber, let’s dive in to how tides work!


The moon! Yes, the moon plays a big part in the tides on our planet the sun does as well but since the sun is further away from the Earth than the moon is, the moon is left as the major player, based on how gravity works.

Very simply, the Earth and moon’s gravitational fields act upon one another, which is what keeps the two objects spinning around each other. Because the rocky part of the Earth doesn’t bend due to the pull of the moon, we don’t notice “land tides”. But because water is much more fluid than rock, the water, rather than the rocks will be pulled towards the moon.


So if some of the planet’s water is drawn towards the moon, it has to come from somewhere, so the areas from which the water is taken experience a low water level. So the part of the Earth facing the moon always experiences high tide. The side opposite the moon also experiences a high tide due to the centrifugal force of the Earth and moon spinning around each other. So at any given time on the planet there are 2 areas of high tide, and perpendicular to the high tides, 2 areas of low tide. Those tidal areas, from our perspective on Earth, cause sea level to go up for about 6 hours, then down for about six hours, completing approximately 2 full cycles a day.


One of the first questions I often hear from people is “why isn’t the tide at the same time every day”? Notice in the previous paragraph I said “about 6 hours”? Well that’s because while the Earth is spinning on its axis every 24 hours, the moon is also orbiting around the Earth at a rate of once every 28 days or so. What this means is that while a solar day (the time from noon to the next noon) is 24 hours, the “lunar day” is 24 hours and 50 minutes. So for our purposes in the waters around Wilmington and Masonboro Island, the high tide tomorrow will be just over an hour later than the high tide today.


Our next article will discuss tidal currents and how they affect kayakers in the Cape Fear region.


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