Almost everyone has heard of tides at the beach. This is a phenomenon that occurs periodically and is capable of moving large masses of water inland or outward from the shore. The force behind this movement of water masses is the gravitational pull of the moon and the sun on the Earth's surface. The moon is the satellite that exerts the strongest force on these tides, combined with the attraction of the sun, whose mass is much greater.
In this article, we'll explain how tides are formed and what they depend on. We'll also discuss what tide tables are and their usefulness in sport fishing. Want to learn more about tides and tide tables?
How do they work
In addition to the combined effects of the moon and the sun on Earth, we must also consider the effects of Earth's own movements, such as rotation and revolution. The Earth's rotation exerts a force known as centrifugal force. While many forces contribute to this phenomenon, the moon undoubtedly exerts the greatest force. If you'd like to learn more about the moon's role, you can read about the tides and the moon.
The tides operate cyclically. Since the Earth takes 24 hours to complete a full rotation, it would once be perfectly aligned with the moon. Logic tells us that there should only be one high tide per day. But this isn't the case. There are two high tides with 12-hour cycles and low tide in between. Why does this happen, and not as logic would suggest?
Let's explain step by step. Since the Earth and the Moon form a system that rotates around a center of rotation, it is the Moon that attracts the waters when it is in a vertical position, causing them to rise. On the other side of the Earth, the same thing happens thanks to the centrifugal force generated by the Earth's rotation . This high tide that occurs on the opposite side of the Earth is less intense.
However, on faces that are not aligned with the moon, the opposite occurs. The gravitational and centrifugal forces counteract each other and result in low tide.
Tidal cycle
We need to consider the Earth's movement to fully understand this cycle. As the Moon rotates on its own axis, it also revolves around the Earth. It takes about 29 days to complete its orbit. This is why the Earth isn't exactly aligned with the Moon every 24 hours; it takes slightly longer (approximately 50 minutes). This difference is called a lunar day, and it's what governs the tidal cycle.
Therefore, the complete cycle between high tide and high tide is 12 hours , while the cycle between high tide and low tide is 6 hours. This isn't always so precise, since our planet isn't composed solely of water. There are land surfaces with irregularities that influence the tides. The geometry of coastlines, the depth profile of coastal areas, ocean currents , the prevailing wind, and latitude also play a role. Sometimes, atmospheric pressure also has an influence.
Types and table of tides
As we've discussed, it's the moon's gravitational pull that exerts the greatest force on the waters. But there are several types of tides. On the one hand, we have spring tides. These are a type of high and low tide that is more pronounced and occurs when the moon and the sun are aligned over the Earth. It is then that both forces pull on the waters with greater force, resulting in both higher and lower tides. If you'd like more information, you can consult about how a delta forms in relation to the movement of water.
The opposite also occurs. When the Sun and Moon are at a right angle, the gravitational forces are weaker, resulting in minimal gravitational pull. It is at these times that tides are smallest and are called neap tides. If any of the variables affecting tides mentioned above are significant, storm surges can occur.
Tide tables are compilations of high and low tide times. They are very useful for planning sport fishing trips. Thanks to these tables, you can know when high and low tide will occur. Furthermore, they help estimate fish activity, increasing or decreasing the likelihood of catching fish.
Here is an example of a tide table:
Are there tides in the Mediterranean Sea?
Compared to other seas and oceans, high and low tides are barely noticeable in the Mediterranean Sea. This is because it is a virtually enclosed sea. The only opening is the Strait of Gibraltar, through which there is an exchange of water masses with the Atlantic Ocean.
The strait acts like a tap, shutting off the flow of water and preventing tides from becoming too pronounced. Because such a large volume of water has to pass through such a narrow passage, strong currents are generated, but they are not fast enough to significantly alter water levels during the tidal cycles.
During the emptying part, the opposite occurs. There is a fairly strong outflow current that heads towards the Atlantic. Therefore, since the Mediterranean is a fairly small and closed sea, although the tides are noticed at the level of the coast so that they rise or fall centimeters, it hardly alters navigation. It is true that whoever is on the shore of the beach will notice the change throughout the day. But beyond that, it doesn't matter.
I hope this information helps you learn more about what tides are and how they work.