One of the things that’s taken me somewhat by surprise in researching for this blog is the precision that modern radiometric dating methods can achieve. To give just one example, a few years ago researchers at Glasgow University pinned down the date of the K/T impact event, which killed off the dinosaurs, to within just eleven thousand years of 66,038,000 years ago. That’s an accuracy of just one part in six thousand — far tighter than I ever expected!
For what it’s worth, tolerances as tight as these completely falsify the oft-heard young-earth claim that radiometric dating is “guessing at best,” or that long ages are merely a presupposition to try and make space for evolution to happen. It is simply not possible to get results that specific out of vague and non-specific starting points, and “evolutionary presuppositions” are about as vague and non-specific as you can get.
Such high precision results are also the exact opposite of what we see in claims of evidence for a young earth. YEC arguments routinely rely on extremely low precision measurements with huge error bars, poorly known quantities, and rates that nobody expects to have been the same in the past as they are today.
The ninth entry on Answers in Genesis’s top ten list is a textbook example of this. It is the claim that there is not enough salt in the sea for an old earth. This argument says that if you tot up what goes in and what goes out, and divide how much is already there by the difference, you get an upper limit, and the earth (or at least, the oceans) can’t be any older than that.
Exactly what limit does this place on the age of the earth?
Everyone who cites this argument seems to have different ideas about what that upper limit actually is. Many rank-and-file YECs think it’s just a few thousand — I’ve had one person quote me 6,000 and another person quote me 100,000. This person quotes Kent Hovind as thinking it is 5,000 years.
For the most part, if you’re quoting figures this low, you probably just saw this argument on your Facebook feed, shared it without clicking through to read it, and blindly assumed that it must have been somewhere in the region of six thousand years or only slightly more. In actual fact, Andrew Snelling, Answers in Genesis’s geologist-in-chief, who wrote the article in the first place, gives a figure of 42 million years, citing the 1990 paper The Sea’s Missing Salt: A Dilemma for Evolutionists by YEC scientists Steve Austin and Russell Humphreys.
As evidence for a young earth, that is a joke. 42 million years may differ from the modern scientific consensus on the age of the earth by a factor of a hundred, but it also differs from the YEC timescale by a factor of seven thousand. If we are to concede that this falsifies the scientific consensus on the age of the earth, we must also insist that it falsifies the young-earth timescale seventy times more forcefully.
But does it falsify the scientific consensus anyway? In order to answer this question, we must address a question that we need to ask of all young-earth claims.
How large are the error bars?
There’s a deep and fundamental problem with trying to use the amount of salt in the sea to estimate the age of the earth. We are dealing with quantities that are extremely difficult to pin down, highly sensitive to changing climatic and environmental conditions, and as such can not be realistically assumed to have been the same in the past as they are today. There are a lot of different inputs and outputs, some of them not fully understood or completely quantified even today, and it’s very easy to overlook some of them. Even measuring the known quantities is a gargantuan task, requiring massive multi-national surveys over long periods of time. Enormous error bars are par for the course. The values involved change constantly as new and more detailed surveys are undertaken.
Nevertheless, the amount of salt in the sea was actually the basis for some of the earliest attempts to estimate the age of the earth in the pre-radiometric era. The first people to try and come up with a figure were Edmund Halley (1715) and John Joly (1899). Joly’s figure was 90 million years (Hay et al, 2006). More recently, Daniel Livingstone (1963) used data by Clarke (1924) to come up with an estimate of a few hundred million years, with a very wide margin of error that could extend as high as 2.5 billion years. The modern scientific consensus, taking all known data into account, now considers that long-term rates of influx and egress are equal within error bars, and consequently the amount of salt in the sea tells us nothing whatsoever about the age of the earth. (Holland, 2006.)
It is error bars, not evolutionary presuppositions, that have caused scientists to abandon the salt chronometer in favour of radiometric techniques. No matter what your worldview, it is outright ridiculous to reject high-precision results, accurate to one part in 6,000, in favour of low-precision methods whose errors can be ±50% or more.
Of course, Snelling describes all this as a “rescuing device,” and says that “even the most generous estimates” give an upper limit of just 62 million years. However, besides not taking everything into account, Austin & Humphreys’ paper was based on outdated data.
A case in point: halite deposits
One of the most important processes by which salt is removed from the oceans is by evaporation. This leaves behind massive deposits of halite, which can be found in numerous places all over the world. One of the largest halite deposits is found underneath the Mediterranean. There is a lot of evidence that from 5.96 to 5.33 million years ago, the Strait of Gibraltar repeatedly closed off, causing the Mediterranean to dry out and depositing vast quantities of ocean salt on the sea floor. This period, the Messinian Salinity Crisis, came to an end 5.33 million years ago when the Strait of Gibraltar was finally breached one last time and the Mediterranean rapidly re-filled in an event called the Zanclean Flood. A speculative future recurrence of this flood was portrayed in the award-winning xkcd webcomic episode, “Time,” a few years back.
This episode would have removed a substantial fraction of the salt in the oceans. So too would other large halite deposits that can be found all over the world, in places such as the Dead Sea and the Gulf of Mexico. Austin and Humphreys cite a figure of 4.4×1018 kg for the worldwide inventory of halite, citing Holland (1984). They claim that it is “extremely unlikely” (page 8) that this contains a significant error, as “No major quantity of halite in the earth’s crust could have escaped our detection.”
In actual fact, it turns out that major quantities of halite deposits had escaped our detection, and in the past three decades, many more such deposits have been found in the course of oil exploration. Hay et al (2006) give much more up to date estimates of between 19.6×1018 kg and 35.2×1018 kg, or between four and a half and eight times greater than that cited by Austin and Humphreys. Furthermore, they state that these figures are most likely incomplete (they include no data from Antarctica, for example), and that further exploration and surveys in the future may well push the figure up even higher. They also conclude that, far from increasing, the amount of salt in the oceans has actually decreased since Precambrian times.
Austin and Humphreys’ paper also overlooks several other factors. Glenn Morton points out for example that there are no less than sixteen different known mechanisms for sodium removal that they omitted to take into account, such as plankton concentrating sodium in their bodies, which is then removed from the oceans as sediment when they die.
The 2006 paper by Hay et al (full content here) is a good, comprehensive scholarly survey of the amount of salt in the oceans. It is a lengthy read, but it is easy to understand and it presents a lot of useful data. However, it should be abundantly clear that, once modern, up to date figures are used and all known vectors are taken into account, and given the huge uncertainties and variabilities in the values concerned, the amount of salt in the oceans tells us nothing whatsoever about the age of the earth.
Featured image credit: Gail Hampshire (via Wikimedia Commons)