The etymology of tide takes us to the French word marée . An Eastern Gallic term that, in turn, emanates from Latin. Specifically from "mare", which can be translated as "mass of water".
The tide is the movement made by the waters of the sea when they descend and rise alternately and periodically . This oscillation is a consequence of the attraction exerted by the moon and the sun .
Objects that have mass are attracted to each other by the natural phenomenon known as gravity . The moon and the sun, in this framework, exert forces of gravitational attraction on the planet Earth : the tide is the effect of these forces on the oceans.
Due to these forces , tides develop and sea level changes periodically. It is important to keep in mind that changes are also recorded due to rain, wind and other factors that are not linked to the tides.
The continuous and slow rise of marine waters is called flow . When the sea reaches its maximum height, the high tide or high tide is reached. From this point, the progressive descent begins, called reflux . The minimum height, meanwhile, is called low tide or low tide . Then the flow develops again and so on.
From high tide to low tide (and vice versa) it takes approximately six hours . It should be noted that the flow is due to the progressive increase in solar and/or lunar attraction, while the ebb is related to the progressive decrease of said attraction .
Likewise, we must not forget that one of the best-known songs of recent times by the Spanish musical duo Amaral, formed by Eva Amaral and Juan Aguirre, is titled "When the tide rises." This is a song that was presented in 2011 and is found on the album titled "Hacia lo Savage."
Red tide , on the other hand, is the propagation of microalgae in the water in a certain region. These microorganisms generate toxins that affect mollusks: if a person later ingests these animals, they can become poisoned.
The oil spill , finally, appears when an oil spill occurs in the water. These accidents damage the ecosystem in various ways.
In the same way, we cannot ignore that in Spain there is also talk of a green tide. This is the name given to a set of protests against cuts in education that took place during the 2011-2012 school year.
The Community of Madrid was where mobilizations of this type were mainly carried out, carried out, above all, by teachers due to the worsening conditions in the classrooms imposed by the PP. However, they also had the support of parents of students and society in general.
The increase in ratios in nursery schools, the suppression of compensatory classrooms, the notable decrease in the public offer of teaching employment, the reduction of night high school groups and various salary cuts are the situations that led to the so-called green tide. A name it received because the protesters wore t-shirts of that color that read: "Public School of all for all."