When Earth is observed from space, a beautiful bright blue sphere results because three quarters of the planet's surface is covered with water. That is, what stands out in our world is precisely the seas, oceans and the clouds they generate.
Generally there are usually doubts when considering whether seas and oceans are equivalent terms. The answer is no. A sea usually has less extension than an ocean and therefore an ocean is usually formed by different seas. Thus, for example, the Mediterranean Sea is part of the Atlantic Ocean, with which it communicates through the so-called Strait of Gibraltar. The Manche Sea (between France and the United Kingdom), the North Sea and the Sargasso Sea (Florida) are also part of the Atlantic Ocean, among others.
Due to the smaller extent that its waters occupy, this is why we talk about the Black Sea or the Dead Sea and not the Dead Ocean, for example.
To complicate matters further, some seas usually encompass other smaller seas that correspond to areas of this sea that bathe a specific land. In this way, the Adriatic Sea is part of the Mediterranean Sea, which in turn is part of the Atlantic Ocean. Sure, not?
How the oceans formed?
There are several hypotheses to explain the origin of the oceans. Traditionally it has been considered that it was during the first moments of cooling of our planet, when it was an igneous mass that released large amounts of gases that gave rise to our atmosphere and, when it cooled, to the hydrosphere, when numerous rains fell continuously , for days and even years in a row.
However, there are other alternative explanations, such as the one defended by the French scientist Francis Albarède, who considers that the water arrived on our planet brought in the form of ice by numerous asteroids that, diverted from the Oort Belt by the Earth's gravity when crossing that area of the Universe, ended up impacting on the earth's surface.
Let's see it in more detail in "The formation of the oceans".
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