This is the second article in the series titled, “Fossils and Dating and Rocks, Oh My!” Last time I talked about the most common method scientists use to date ancient objects, radioactive carbon (14C) dating. Because carbon dating depends on objective measurements, observations of the environment, and math, many people are very confident that the long ages claimed by measuring radioactive carbon content proves evolutionism is the truth. But as we saw, the problems are not in the method but in the assumptions the method makes.
The assumptions for 14C dating and for the scientific measurement process in this month’s column both depend entirely on claims of the naturalistic worldview where you start out believing the universe came into being by natural processes and is governed by natural laws only. Therefore it changes very slowly over time at constant rates and must be very old. The assumptions behind dating methods do not prove this worldview, they simply require it to be true without proof. Evolutionists don’t like to admit that they start with anything other than their own rationality and their observations from nature. But right from the beginning, they have to start out assuming a godless universe for their methods to work. The validity of your reasoning always depends upon your assumptions, and the naturalistic worldview is the main unspoken assumption behind every evolutionary hypothesis out there. If you wish for more review, I ask you to refer to my last article or to read the Institute for Creation Research (ICR) website’s article on the same subject here.
The validity of your reasoning always depends upon your assumptions, and the naturalistic worldview is the main unspoken assumption behind every evolutionary hypothesis out there.
So what about the dating methods for rocks that are not biological in origin and cannot use 14C for their dating method? Geological ages of millions and billions of years are frequently claimed by scientists and used as proof of long ages and confirmation of the evolutionary assumptions. This time I’ll briefly discuss one of these dating methods and show you that it is not very different than 14C in its assumptions and its truth claims. I’ll keep it as simple as I can, but believe me, there is enough material in this subject area to sink several lifetime’s worth of research into, and this is not my area of expertise. However, we can all evaluate the work of expert geologists and compare discordant claims to understand the truth.
The most well known dating methods for geologists all have to do with the decay rates of various radioactive materials. Such decay rates are generally predictable under current conditions, although variations have been seen as I will outline later. First, recall that an isotope is any one of a variety of atomic forms an element may be found in. Isotopes of the same element differ in the number of neutrons they contain in the nucleus, and thus they have different atomic weights. Some isotope configurations are unstable, like a tower of blocks that is too heavy on top. These isotopes break down into other isotopes and elements through radioactive decay.
In radioactive, decay atoms of an unstable isotope (a radioisotope) shed particles from their nuclei, transforming themselves into “daughter” elements. For example, the unstable uranium isotope 238U decays through several such stages to become a very stable isotope of lead, 206Pb. Similarly, another uranium radioisotope, 235U, decays to its own unique lead isotope, 207Pb, and thorium (232Th) decays, ultimately, to yet another unique lead isotope, 208Pb. Natively, lead is 204Pb. We know of no other way for these heavier isotopes of lead to form. Each daughter isotope is believed to uniquely come from its parent.
Under current conditions, these decay rates can be observed very precisely, resulting in projected half-lives for 238U, 235U, and 232Th of 4.47, 0.704, and 14.1 billion years, respectively. But too often radioisotope dating is presented as an infallible measure of the passing of time. Many books have been written on this subject and there is an abundant amount of data. But careful interpretation of this data may show that radioactive decay does not always determine sample age as the promoters of these methods would have you believe. The basic assumptions all radioisotope dating methods relies on are:
- The amounts of parent (238U, uranium) and daughter (206Pb, lead) were set when the rock formed and they haven’t changed except by radioactive decay.
- The rates of decay have been constant throughout the history of the rock.
- The rock sample has not been contaminated.
There are a few other more complex assumptions that are made, but we will only deal with these here. If any of these assumptions are proven unreliable the whole dating method becomes suspect. Over billions of years, the third assumption is probably completely impossible to guarantee. And as we will see, the second assumption is also particularly hard to prove reliable.
If any of these assumptions are proven unreliable the whole dating method becomes suspect.
Suppose we find a rock sample we wish to date. We crunch it to fine powder and separate out the minerals in it. We use an instrument called a mass spectrometer that shoots a laser beam at the mineral samples and burns them up. You may have noticed that, when burnt, some materials produce different color flames. Mass spectrometers are very precise instruments that work on this principle. They measure the different frequencies of light coming from the combustion and determine what concentrations of elements must have been in the sample as it is destroyed.
A well trusted method of dating rocks, the isochron method, supposedly tells the age of the sample and how much daughter element was already in the rock when it crystallized. To draw an isochron plot, you need to have three types of element present: a radioactive parent (238U), its daughter element (206Pb), and a stable element whose concentrations must not have changed over the history of the rock (204Pb). The concentrations of both the parent element and the daughter element are divided by the concentration of the third element and plotted against one another. For some rather complex reasons you can read about here, if the relative concentrations of 238U to 204Pb and 206Pb to 204Pb in each mineral or whole rock sample line up in a straight line, this is an indication that the dating method gives a very accurate measure of the age of the samples and the amount of the daughter element initially present.
Because the isochron method makes very few assumptions and is based on measurable concentrations in the rocks, scientists tend to think it is a completely reliable measure of the age of a sample. There are many types of isochron methods that employ different parent and daughter isotopes, and if all of them are very accurately measuring the age of the rocks they should all agree. If they do not agree, then their accuracy must be questioned.
Unfortunately for the theory, very frequently, isochrons of different elements from the same rocks do not match. In fact, they are often not even close. The dates derived from this method come with a statistical guarantee of accuracy, but much of the time the differences between two different “reliable” methods return unreconcilably different dates with hundreds of millions of years difference. If two atomic clocks disagreed by 100 years you would come to the conclusion that at least one of them was set wrong. Similarly, the very accuracy of the isochron method requires that all the measurements should be very close to the same. Since they are often not, this shows that the method is flawed. Some other unknown process is going on that should explain the inconsistencies. As a side note, geologists have to pick one of these divergent “ages” as the official age of the rock. And they often do this in an interesting way I hope to discuss next month.
It is not enough to simply find a problem with the current methods, we must also have a reasonable alternative hypothesis that better explains our observations. First, scientists have noted that heavier elements like uranium typically show much older isochron “ages” than lighter elements like potassium (Snelling, 2005). Similarly, one form of decay (alpha decay) typically produces older dates than the other form (beta decay). Finally, elements with longer present-day half-lives produce older dates than those with short half-lives. This tells us that we may not fully understand the decay process over time.
Young-earth creationists believe that the decay rates must have changed dramatically over time (in violation of evolutionary assumption #2, above). And there is some good evidence of this that cannot be explained by the evolutionary understanding of the processes involved. For instance, helium is a byproduct of one kind of alpha decay. But helium escapes rocks rather quickly, as anyone who has ever bought a ballon for his child only to find it sadly deflated the next morning can understand. If helium were formed deep in the Earth’s crust, it would take only 8,000 years to escape from the depths into the atmosphere. If these rocks are truly as old as we are being told, any sample over 8,000 years of age should have almost no helium in it. However, what we find is that much of the helium produced by radioactive decay is still in the rocks, and sometimes even in the crystals where it was produced. No known natural process could keep it there longer, so that would imply all the billions of “years” of decay actually happened over less than 8,000 years.
Another accidental finding that contradicts the idea of constant decay rates over deep time is that the sun actually seems to affect these rates. Two separate processes have been noted: radioactive decay rates have been shown to vary seasonally and diurnally (Mullins, 2009) and decay rates accelerate when part of the sun’s core that produces intense bombardments of neutrinos is aimed at Earth (Stober, 2010). Neither of these processes has a know physical explanation, yet observations were made of changes in a supposedly constant process of radioactive decay. This means that decay rates are not a closed system uninfluenced by external factors.
Conditions during the Flood year could have precipitated rapid radioactive decay. It is my personal educated guess (although remember, I’m no geologist) that the Flood was caused by runaway nuclear fission reactions within the mantle of the Earth that produced the heat necessary to open the “fountains of the great deep” and produce both the volcanic devastation that is so clearly preserved in the fossil record and the massive amounts of radioactive decay that account for those supposed billions of years.
There are many other problems with radioactive dating including funny stories like 10-year-old lava formations from Mount St. Helens being dated at 340,000 years of age (Austin, 1996). These problems show that we do not have such a complete understanding of these processes that we can rely on them to validate extreme claims of old age for the Earth. If you would like to read more about some of these problems, the Institute for Creation Research has some great articles on the subject. Rocks don’t lie, but people sometimes do. And sometimes people are just deceived. This is why I find it reassuring that I can rely on the Word of God as my source of truth, no matter what other scientists are saying this week. Next time I plan to talk about what can go wrong when a rock dates a fossil. Until then, remember, stand on the unchanging Word of God, and you will be safe from the changing opinions of fallible men.
A. A. Snelling, “Isochron discordance and the role of inheritance and Mixing of radioisotopes in the mantle and crust.” Chapter 6 in Radioisotopes and the Age of the Earth, vol 2, 2005.
Mullins, J. 2009. Solar ghosts may haunt Earth’s radioactive atoms. New Scientist. 2714: 42-45.
Stober, D. The strange case of solar flares and radioactive elements. Stanford Report. Posted on news.stanford.edu August 23, 2010, accessed August 25, 2010.
Austin, Steven A. 1996. Excess Argon within Mineral Concentrates from the New Dacite Lava Dome at Mount St. Helens Volcano. Creation Ex Nihilo Technical Journal. 10 (3): 335-343.