NATURAL PHENOMENA

The Challenge of The Qur’an ~ 355 ~ and flow of the sea, have large quantities of saltwater gush upstream at high tide but, again the waters do not mix. The salt water forms an upper layer, the fresh water remaining below it. At ebb tide, the salt water recedes, leaving the fresh water, as it was before. Man had observed such natural phenomena from ancient times, but he did not know the laws of nature which governed them. It has recently been discovered by modern research that the way liquids flow is governed by a difference in salinity and thus density because saline water is denser than fresh water; when two water bodies converge, the more saline of the two flows beneath the less saline. Thus, a river flowing into the sea flows on the surface, sometimes for great distances; the Mississippi, for example, appears as a brown, fresh-water stream in the blue waters of the Gulf of Mexico. Salinity variations in the oceans and seas are partially responsible for large-scale seawater circulation. A well-known example is the flow to the Mediterranean Sea, which is separated from the North Atlantic by a sill, 320 metres (1,050 feet) deep,