Review by Greg Neyman
© Old Earth Ministries
Published May 2006
In this chapter, DeYoung summarizes the research done by Russell Humphreys on helium retention in zircon crystals. The original work done by Humphreys is online, and can be read if you prefer to delve into the technical literature. There is a history behind these works. Here, in chronological order (as near as I can figure), is the articles in this series of discussions and rebuttals.
Helium Diffusion Rates Support Accelerated Nuclear Decay, Published 2003. This first study is actually by four young earth theorists, Humphreys, Steven Austin, Andrew Snelling, and John Baumgardner.
Helium Diffusion Age of 6,000 Years Supports Accelerated Nuclear Decay, Published 2004 in CRSQ. This is also by the same four theorists
Young-Earth Creationist Helium Diffusion "Dates", Published 2005?, by Kevin Henke. This lengthy rebuttal points out the problems in the helium research
Helium Evidence for A Young World Remains Crystal-Clear, Published April 2005, a response to Henke's article, written by Humphreys
Young-Earth Creationist Helium Diffusion "Dates", Published 2005. This is Henke's response to Humphreys April 2005 article
Since the summary in this book by DeYoung is a non-technical summary, I will attempt to do the same thing.
DeYoung tells that in 1974, a bore hole was drilled through basement rock in New Mexico, at a location known as Fenton Hill. The drill team measured the underground temperatures as they drilled, and this data is relied upon in the young earth calculations. Some of the rock samples were obtained by the young earth creationists. Initial work in helium diffusion was done by a young earth creationist named Robert Gentry, who is famous for proposing a young earth via polonium halos, another young earth theory which has proven to be false.
RADIOACTIVE ZIRCON CRYSTALS
The rocks we are concerned with is basically a granite, composed of quartz, feldspar, and biotite. The biotite, or black mica, contains the zircon crystals. The zirconium atoms can be replaced by uranium and thorium as impurities. The nuclear decay of the uranium produces stray alpha particles, which combine with free electrons to become helium atoms. The helium, being a tiny gas, escapes, or "diffuses" out of the zircon crystals.
The problem, according to the young earth study, is that there should be no helium in the zircons, as it has had 1.5 billion years to diffuse out of the crystals. However, zircons from a depth of 1,000 meters was found to still contain 58 percent of the total helium that should have been generated by past nuclear decay.
DeYoung claims that there are two possibilities. There is either a problem with the assumed time scale (i.e. the rocks are not 1.5 billion years old), or there is a problem with our understanding of how helium moves through rocks. However, neither is a problem. DeYoung fails to mention the real problem. The young earth research is faulty.
RATE RESEARCH ON HELIUM DIFFUSION
First, RATE looked into the possibility that the biotite mineral surrounding the zircons could act as a barrier, keeping the helium trapped. RATE commissioned an outside scientist to help determine the answer to this possibility. First, samples from the Beartooth Mountains in Wyoming were analyzed, and showed that the helium freely moved through the biotite. Encouraged by this, they then obtained some rock samples from the 1974 drilling at Fenton Hill in New Mexico. First, samples from a depth of 750 meters was tested, yielding similar results.
RESULTS OF HELIUM DIFFUSION IN ZIRCON
Next, samples from a depth of 1,490 meters were tested. This test led to the chart that DeYoung relies upon heavily, on page 74. In short, they analyzed the amount of helium that should have accumulated over the supposed life of the mineral (1.5 billion years), and showed that the amount of helium remaining in the mineral was too high. After 1.5 billion years, given the ease with which helium diffuses out of the zircons, there should be little helium remaining.
The chart shows that using an assumption of a young earth, the amount of helium in the zircons is a much better fit than the old earth, uniformitarian model.
DeYoung says that some critics of this young earth explanation have brought up the issue of closure temperature. Closure temperature is the temperature at which the helium atoms do not have sufficient energy to escape the zircons, and thus if the temperature were below this level, the helium could be trapped for billions of years.
He contrasts that with the "real meaning" of closure (as if the old earth scientists did not understand this!). This real meaning, understood by all, is the temperature at which the rate of helium formation via uranium radiation exceeds the amount of helium escaping from the crystal, or in simple terms, more helium is being created than is escaping.
We know that closure does not seal the crystal and trap all the helium inside. And, we know that at some point, the zircon must lose helium just as quickly as it is produced (when it reaches this point of equilibrium). The point is that helium can be retained in the crystal in higher quantities than can be expected at higher temperatures.
FURTHER DISCUSSION OF ZIRCONS
Finally, DeYoung explores the claim that biotite, as a mineral that forms in thin layers, traps the zircon crystals between the layers, and seals it. Since helium freely moves through the biotite as well, there is no reason to discuss this "flaky" argument.
Are these young earth claims about zircons true? Not at all. Although this is a noble attempt to do some real science, they failed to consider all the variables in their studies. Here are the problems. Note that although some of these are addressed by Humphreys in a rebuttal, he fails to answer these issues.
1. In the experiments to see how readily helium diffused, they did use one variable, temperature, but they failed to use another one...pressure. Subsurface pressure is great at depth, especially 750 and 1,490 meters deep, the depth of the samples used. This increased pressure would have a great affect on the ability of the helium to diffuse. This fact alone invalidates the young earth experiments.
2. The Fenton Hill site has undergone several periods of faulting and volcanism (it is only a few kilometers from Valles Caldera). This caldera contains excess helium as well. Thus, contamination by outside helium is a real possibility.
3. In the scientific study published by Humphreys and his associates, they do not report on the variabilities and do not give measurement errors. Unlike real peer-reviewed articles, other scientists have no way of interpreting how accurate their results are.
4. When examined, the Q/Q0 values (fraction of helium retained) contain math errors, and report values too high.
5. Humphreys did give their total data in the study, in Appendix C. However, when you total them for the 750 meter deep zircons, the helium greatly exceeds the amount that would be expected from 1.5 billion years of uranium decay. This clearly indicates an outside source which provided excess helium to the rocks in question.
6. The most damaging information to the young earth theory is not even addressed here. The RATE group acknowledges that billions of years of radioactive decay has occurred, however, they feel that it occurred within two time frames...during the creation week, and during the year-long flood. However, condensing that much radiation into a one-week period, or into a year-long flood, would produce enough heat to vaporize the earth! Humphreys does recognize this heat problem, but provides no solution.
7. Helium is a gas, and it diffuses, or passes through the rocks. Referring to the original studies, zircons from a depth of 1,000 meters had 58 percent of their total helium (total being the amount produced by 1.5 billion years worth of accumulation), and rocks from 2,900 meters deep had 42 percent. Since helium rises, one would expect as the helium navigates upwards, that the shallower rock would have more helium present, which is what they found. Helium which formed from radioactive decay at 2,900 meters deep would rise, and it would enter other zircons on its way to the surface. One cannot assume that the helium in a particular zircon was only formed within that zircon.
DeYoung says this higher level is expected at the top due to lower temperature. He is partially right. With lower temperature, you may reach the closure temperature. However, you also have less pressure, which must be considered also.
8. A point not even addressed by Humphreys in his rebuttal (he fails to provide rebuttals for several critiques) has to do with secular equilibrium. Basically, as uranium decays to thorium, it reaches a point at which the rate of thorium decay equals its production, after which its concentrations remain constant. Uranium decays in a series of events, from uranium to the final product of lead. This series contains elements with half-lives of well over 10,000 years. If these decay rates changed suddenly (i.e. the young earth theory of accelerated decay), then we would not expect to see these elements in secular equilibrium. However, uranium ores do indeed show secular equilibrium, and clearly indicate they have been in a fixed, constant decay rate for at least the last two million years (the extent of the current research goes back this far).
These points are merely a summary of the complete rebuttal done by Henke and others. As you have time, I urge you to investigate this matter for yourself.
Old earth creationists can rest assured that none of the evidence concerning helium diffusion in zircons indicates a young earth.
For Further Reading
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