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It is likely that you have ever witnessed on a beach or coast how the sea can rise and fall a few meters. What is the reason for this? Would you like to understand why the tide rises and falls? The answer is found in the two stars closest to our planet: the Sun and the Moon.
You want to know more? If so, continue reading this interesting and educational article by Green Ecologist about what are the tides and why do they occur.
What are the tides
We begin this article by defining the tide concept. The tides are regular or periodic variations in sea level of the order of several meters and are caused by the force of gravitational attraction jointly exerted by the Moon and the Sun on the Earth. This change in sea level occurs at intervals of a few 6 hours approximately and, in addition, there are several types of tides, as we will see later.
In addition to the tides that affect the waters of seas and oceans, there are other types of movements that occur periodically and for the same reason. They are the tides that occur in the atmosphere (with changes of several kilometers) and in the lithosphere (with small variations that can hardly be perceived).
Why the tides occur
We continue this article explaining how the tides are produced. As we have already indicated, the cause of the tides is in the force of gravity exerted by the Moon and the Sun. In other words, these two stars attract water from seas and oceans to each other, modifying their level.
Now, Newton's law of gravitational attraction tells us that this force depends on the mass of the bodies and also on the distance that separates them. In this way, although the Moon is much smaller than the Sun, the attraction it exerts on the Earth is much greater than that of the great solar star (two to three times more). This is because the Moon is much closer to our planet than the Sun. Therefore, the moon and the tides have a strong bond, being the lunar tides (that is, those caused by the Moon) more important in amplitude than those caused by the Sun astro.
But there is still more, because depending on the different positions that both stars have with respect to our planet, different types of tides can be produced, since the gravitational pull will be different in each case. It is also relevant to comment that the flattening of the Earth (since it is not a perfect sphere) varies with this tidal phenomenon (remember that three-quarters of the planet's surface is covered with water).
What are the types of tides
As we have already been anticipating, there are different types of tides and they are classified based on several criteria. Depending on the height that the sea water reaches, the tides can be of two types:
- High tide or high tide: When the sea level reaches its highest level, we will have high tides, which occur approximately every 12 hours.
- Low tide or low tide: at the moment when the sea level reaches its lowest level, we will have low tides, which also occur approximately every 12 hours.
Therefore, since the low tides and high tides have a periodicity of 12 hours, both follow each other alternating in an interval of 6 hours. Likewise, when we have high tide in one part of the globe, there will be a low tide just in the opposite part.
The following classification of types of tides It is according to the phases in which it is Moon:
Spring tides
They happen when we have Full Moon and New Moon, since it is in these lunar phases when the Sun and the Moon are aligned, allowing to achieve a greater gravitational effect. Spring tides are, therefore, the largest.
Neap tides
They occur when the Moon is in the phases of last quarter and of crescent quarter, since it is in these phases when the two stars meet at antagonistic points (forming an angle of 90º to each other) and compensate for their attractive forces. Neap tides are therefore the smallest.
We could also talk about lunar tides and solar tides depending on whether they are caused by the Moon or the Sun respectively, although the forces of both always influence to a greater or lesser extent.
In this other post you can learn about the phases of the moon.
Consequences of the tides
Have you ever wondered about tidal effects?
- It is well known among fishermen that when there are high tides they usually fish a more fish. Plus, it's even easier to fish when low tides add in.
- It is also convenient for divers and surfers to know about the types of tides and when they will occur in order to plan their activities.
- Besides changes in water depth, it is also important to know that tides can produce uncontrollable ocean currents that can influence the speed and course of the ships, as well as cause some person to be unfortunately dragged into the interior of the ocean.
- Another of the consequences of the tides is that they are capable of generating the ideal conditions for the specific ecosystem of the intertidal zone. It is an ecosystem that is adapted to both marine and aerial conditions, with typical fauna such as some mollusks, crabs, starfish and sea anemones. Among the flora we can find various species of algae.
How to tell if the tide is high or low
How can you tell if there is a low or high tide at the moment in which we are observing it? To find out, it is appropriate that you take into account the periodicity of which we have spoken previously, as well as the phase in which it is. Moon at that moment.
In addition, a very clear indication that the tide is going out is the fact that we see foam residue and other debris. Without forgetting, of course, that we can find specific flora and fauna of the intertidal zone.
However, with a simple internet search, you can find tide tables in each area that will give you an answer to this question.
Why are there tides in the Cantabrian Sea and not in the Mediterranean?
Finally, if you are looking for an answer to why there are no tides in seas such as the Mediterranean and there are in other seas such as the Cantabrian, we will tell you below. Even if the Moon is capable of attracting huge bodies of water, its gravitational force not as effective with smaller bodies of water as, for example, that of the Mediterranean Sea.
However, it cannot be said that there are no tides, but that these they are not as powerful or noticeable. If, for example, the tides of the Cantabrian Sea are one and a half meters, those of the Mediterranean may only reach 50 centimeters, but yes, this phenomenon also occurs.
To further expand your knowledge about tides, we advise you to read these other articles by Green Ecologist about oil slicks and the Effects of a red tide.
If you want to read more articles similar to What are tides and why do they occurWe recommend that you enter our Nature Curiosities category.
