Ocean Salinity as a Failed Scientific Clock

By Ryan McGillivray

Throughout recorded history man has longed to understand his surroundings and environment. Science was born from these observations of the natural world. One of the most important questions raised about the world it is. Over time, many different methods of dating the Earth have been attempted, with most of them failing. One such failed dating technique is measuring the present salt content of the ocean to create a time scale to determine how long it has existed. This technique was introduced nearly 300 years ago, and it was researched by many prominent scientists for several hundred years until it fell out of favor because of obvious drawbacks in the method. Curiously, the salt clock method is somewhat of a controversy even today as proponents of a young Earth model are resurrecting it as proof of an allegedly 6,000-year-old Earth. To understand how valid dating methods work, one must explore invalid methods such as the ocean salt clock and know why and how it is ineffectual. One must also know the history of the method and how it came to be.

One very handy aspect of this method is that measuring salt in the oceans is quite easy because of its abundance. If one cubic foot of sea water is evaporated, it will yield approximately 2.2 pounds of salt (Swensen). The relatively simple method of measuring the salt, along with its abundance is what made this a very appealing dating method to some. Before getting into measuring the salinity of the oceans, one must first understand exactly why the oceans contain salt and how it gets there. salt cycle As rain falls on land, it picks up small granules of dirt and minerals, some of which dissolve into the water itself. As the water makes its way back to the ocean, it contains a large load of dissolved minerals, a lot of which is salt. What makes the ocean salty is that when water evaporates off of the ocean, it leaves its load of dissolved salt behind and becomes fresh. Then as the water condenses into rain, the cycle starts all over again and brings more salt to the oceans. The chart below shows the cycle of how salt is carried from land to the oceans.

Theoretically, in a closed system, measuring the salt content of a body of water would work to calculate an approximate age. Imagine an initially fresh body of water in which salt is continuously added. If a somewhat constant rate of accumulation of the salt is known, and the present amount of salt in the water is known, then a simple algebraic calculation would render the age of that particular body of water. This is exactly what many people have tried to do over the years.

Edmund Halley first addressed the method of testing the ocean's salinity in 1715. Halley, an astronomer, was the first real proponent of using the salt clock to calculate the age of the Earth. He was the first to observe that oceans and certain lakes were fed by streams and were therefore constantly receiving more salt. Halley could not test his theories, however, because he needed to know the salt content of the oceans earlier in time to calculate a rate of accumulation (Dalrymple, 2004, p 39). In 1876, T. Mellard Reade looked into this process and renamed it chemical denudation. Reade came up with a calculation that it would take 25 million years for the sulfates of calcium and magnesium to reach their present concentrations in the oceans. Others tried the method, yielding similar dates. John Joly calculated an age of 99.4 million years in 1899. Ten years later, Joly revised his equations and calculated the age to be between 80 and 150 million years old. George F. Becker found the age of the Earth to be between 50 and 70 million years old when he used the salt clock method in 1910 (40-41).

The dates calculated by all who attempted this method were wrong because of several fundamental flaws in the system. First of all, to use the salt clock as an actually clock, you must assume that the starting point would be 0% salinity. This, of course, could never be known because no one was around to measure the salinity of the oceans right when they formed. Also, people assumed that the ocean is an eternal reservoir, and when the salt is dumped in the ocean, it stays there permanently. This assumption is false as it has been later proved that elements of the ocean are being constantly recycled and leave the water. As plate tectonics shapes our Earth, sea beds rise and evaporate, leaving large salt deposits. Oceanic plates subduct and melt into the Earth which causes volcanoes to erupt which spew material containing salt that becomes incorporated into the land, which then starts the process all over again.

The Earth, including the salt in the ocean, is in a constant state of flux, on a very large cycle. In fact, the amount of salt lost from the ocean and the amount it gains are about the same. This means that the salinity of the oceans does not gradually increase, or even change greatly, but is actually in a state of equilibrium. Another fundamental flaw in this system is that the rates of erosion, solution, rainfall, and runoff cannot be measured over large amounts of geologic time. They simply vary too much to yield any constant (41). Also, the fact that different elements tend to spend different amounts of time in the ocean adds to the confusion of the calculations.

For a process to be considered a good natural clock, it must contain the following: a known initial condition, an irreversible process, a uniform rate, and a final condition. With the salt clock, the initial condition is not known. The process of salt accumulation has been proven to be reversible and in constant change. There is also no uniform rate of accumulation of salt. The only criterion met is the known final condition. Because of these factors, the salt clock can obviously not be used as a natural clock to calculate any type of age.

Despite the known scientific reasons for which this method cannot be used as an accurate natural clock, measuring the salinity of the ocean has recently been used by young earth creationists as supposed proof that the earth is not, in fact, billions of years old. The website Answers in Genesis, a young earth proponent, actually explains the salt clock as a valid measuring device. According to the site, "Many processes bring salts into the sea, while they don't leave the sea easily. So the saltiness is increasing steadily. Since we can work out how much salt there is in the sea, as well as the rates that salts go into and out of the sea, we should be able to calculate a maximum age for the sea (Sarfati)." What is even more curious about this selected article is that the author even cites the works of John Joly and Edmund Haley in his references. The works of Joly and Haley, while vital in tracing the progression of scientific thought on the age of the earth, are in no way current or up to date. The article fails to comment on the shortcomings of the salt clock, and concludes by reiterating that the amount of salt present in today's oceans coincides with the age of the earth according to biblical accounts. To still attempt to use a failed method such as the salt clock as legitimate science is taking a step backward in science. This would be the equivalent of dismissing all modern medicine and going back to bleeding people for virtually any ailment they might contract.

This method of dating the earth, however backward it may seem by today's standards, is nonetheless an important stepping stone in the history of science. If not for trial and errors like this method, it would be impossible to arrive at sound scientific methods and techniques used today. This method is important because it showed critical thinking on the part of man because he was trying to use logic to determine facts about his environment. The spirit or motive of those who used the salt clock is no less valid then any other. This failed clock may at least be remembered in a positive light as a mere step on the path towards discovery and truth.

  1. Dalrymple, Brent G. 2004. Ancient Earth, Ancient Skies. Stanford: Stanford University Press.
  2. Sarfati, Jonathan. 26 October 2005. "Salty Seas- Evidence for a Young Earth." Answers in Genesis. http://www.answersingenesis.org/creation/v21/i1/seas.asp.
  3. Swensen, Herbert. 18 October 2005. "Why is the Ocean Salty?" General Interest Publications of the U.S. Geological Survey. http://www.palomar.edu/oceanography/salty_ocean.htm.