In discussing creation with a friend, we focused our discussion on the fact that the oceans are salty. According to science, where did the salt come from? When earth was first created, was the water that originally covered the earth fresh? Could salty oceans be a result of “the fall” (making the largest source of water undrinkable)? If the earth is millions of years old, why haven’t the oceans dried up from evaporation? Are there springs of saltwater bubbling up from the sea floor?
Of course, it is hard to “prove” what happened in the deep past, but the common sense answer is that the early ocean was not salty. The means by which the oceans became salty is that salt on the land is washed into the oceans by the rivers. At first this may not seem logical, as the oceans are salty and the rivers are not salty, so one might think that rivers would actually dilute the saltiness in the oceans. However, this is definitely not the case. The water in rivers is much less salty than that in the ocean. Typically, the salt content in rivers is about 100 parts per million and the ocean is approximately one thousand times as salty. However, when river water enters the ocean, the water evaporates and the salt is left behind. Over time, the total amount of water in the oceans reaches an equilibrium amount. In any given year, let us say that 60 inches of rain falls, on average, across the earth, but the same amount of water evaporates. What this does is very slowly, but gradually, over many millions of years, the amount of salt builds up in the oceans. Current estimates are that if the amount of sodium ion entering the ocean per year were to continue at the same rate, then the total salt now in the oceans would have reached this level in somewhere near 400 million years. Given that the earth is quite a bit older than this age, it certainly can explain the level of salt in the oceans.
A helpful analogy is found in salty lakes such as the Dead Sea, the Great Salt Lake and others. Such salty lakes are always formed in inland areas with no exit to the oceans. Over time, the amount of salt in the Dead Sea has grown because the water evaporates, but the salt remains behind. Thus the Dead Sea, which is much younger than the oceans, has become very salty–much saltier than the oceans.
The reason the oceans do not dry up from evaporation is that the total amount evaporating from the oceans is in nearly exact balance with the amount entering the oceans through rainfall and inflow from rivers. Are there springs of saltwater bubbling up from the sea floor? The answer is that this is certainly not the principle source of salt in the oceans. There are deep ocean vents which seep into the ocean, but these vents have significant levels of hydrogen sulfide, methane and other gases, but not significant amounts of salt. So, the salt in the oceans arrived there by inflow from rivers. This is the scientific explanation, anyway. There is no indication at all that the oceans became salty in the fall. In fact, the evidence from fossil sea creatures is that the oceans were definitely salty long before the first humans inhabited the earth, and there is not the slightest indication in the Bible that the level of saltiness in the oceans increased at the Fall of Adam and Eve.
Please let me make a general comment. In questions about natural history, it is best to give science the first stab at answering such questions. Coming up with ad hoc explanations (explanations which are created, not because of any evidence, but in order to preserve an already-held opinion) such as using the fall of mankind into sin to explain the salt in the oceans is not a wise approach. I really appreciate the words of Galileo in The Letter to the Duchess Christina (1614). He said “The Bible was written to show us how to go to heave, not how the heavens go.” In other words, the Bible is a theology book, not a science book and it should be read that way. Of course, Galileo is not inspired, but I believe his wisdom here is useful. He also said in the same letter, “In discussions of physical problems, we should begin, not with the authority of scripture but with sense experiences and necessary demonstrations.” In other words, in explaining how nature works, we should begin by examining nature, not the scripture, which was not principally designed to answer such questions.