Qur'an, the last of the Divine Scriptures, was revealed unto Prophet Muhammad ﷺ more than 1400 years ago. The Qur'an at time addressed the coarse and illiterate audience of Arabia who lived a life confined to the wind blowing deserts, far from seas and rivers. Thus, many revelations in Qur'an could not be understood by them for science was perhaps in its very early age and everything that was said was more of speculations rather than solid convictions. And thus, many a Divine Revelation remained unanswered till very late in the 20th century when science began to find hidden meaning of things said centuries ago.
We already talked of the
Theory of Big Bang and Formulation of all living beings with water in our series of posts on "Divine Revelation in Qur'an validated by Scientific Discoveries". Today, we will talk about the separation of two seas when these contain different water densities and formation. Let us first see how this phenomenon is mentioned in Qur'an:
He has set free the two seas meeting together. There is a barrier between them. They do not transgress. (Quran, Sūrah 55 Ar Rehman verses:19-20)
He is the one who has set free the two kinds of water, one sweet and palatable, and the other salty and bitter. And He has made between them a barrier and a forbidding partition. (Quran, Sūrah 25 Al Furqan verse:53)
In Allah's overall scheme of things, bodies of salt and sweet water, which are adjoining and yet separate, have significant functions. Weaving a harmonious fabric out of these different fibres shows both Allah's power and wisdom. Incidentally, this verse points to a fact which has only recently been discovered by science. This fact relates to the oceans of the world: they meet and yet each remains separate for Allah has placed "a barrier, a partition" between them. [1]
Now coming over to the scientific explanation of the phenomena mentioned in Qur'an:
Modern Science has discovered that in the places where two different seas meet, there is a barrier between them. This barrier divides the two seas so that each sea has its own temperature, salinity, and density. For example, Mediterranean Sea water is warm, saline, and less dense, compared to Atlantic Ocean water. When Mediterranean Sea water enters the Atlantic over the Gibraltar sill, it moves several hundred kilometers into the Atlantic at a depth of about 1000 meters with its own warm, saline, and less dense characteristics. The Mediterranean water stabilizes at this depth. [2]
In the diagram above, the Mediterranean Sea water as it enters the Atlantic over the Gibraltar sill with its own warm, saline, and less dense characteristics, because of the barrier that distinguishes between them. Temperatures are in degrees Celsius (C°). (Marine Geology, Kuenen, p. 43, with a slight enhancement.)
This is just one example. There are many places in the oceans where this phenomenon occurs. Those who argue that Qur'an is nothing but brainchild of Prophet Muhammad ﷺ, how would they respond to this phenomenon mentioned in Qur'an 1400 years ago and only validated in recent times, almost five hundred years later, using advanced equipment to measure temperature, salinity, density, oxygen dissolubility, etc. The human eye cannot see the difference between the two seas that meet, rather the two seas appear to us as one homogeneous sea. Likewise, the human eye cannot see the division of water in estuaries into the three kinds: fresh water, salt water, and the partition (zone of separation).
You many now like to view a video on the subject in question and how two bodies of water of different densities and formation are kept from mixing with each other and keep at bay with a invisible barrier in between the two: "Why the Atlantic and Pacific Meet, But Never Mix"