Radiometric Dating Part 4
>> Wednesday, October 27, 2010
There is a common misunderstanding that radiometric dating systems have confirmed the age of the earth. Nothing could be further from the truth. Radiometric dating systems are purported to give ages in the billions of years for the earth’s primary rocks. However, these methods are entirely unreliable giving errors of magnitude. The New Encyclopedia Britannica states that the picture for radiometric accuracy is “gloomy”. Rare attempts to apply multiple radiometric dating methods where mother and daughter elements are both present to rocks from the same stratum “almost always” give disparate dates.
“The uranium-thorium to helium-lead” methods of radiometric dating have been “pushed into the background” due to the “limited applicability and questionable reliability” of these methods. The decomposition of potassium-40 into two daughter elements: argon-40 and calcium-40 is equally fraught with problems.
Among potential wrong assumptions in establishing a date for a rock sample is the original presence of daughter elements. For example calcium-40, a daughter element of potassium-40 decomposition, is abundantly available in the earth’s surface. Only a fraction of this element can be attributed to the decomposition of potassium-40. Therefore, the presence of calcium-40 cannot be used to demonstrate the age of anything.
A second false assumption is that the decomposition processes have remained constant over billions of years. We have not even scientifically observed these processes with any accuracy for 50 years. How can we extrapolate that things have not changed over hundreds of millions or billions of years when we know that stasis of the environment cannot be true? There are many potential variables and conditions that may prove to accelerate or decelerate the nuclear decay processes.
A third problem is that contamination of rock samples is unavoidable. There are many ways that mother, or daughter elements can be falsely introduced or leaked away. Potassium, for example, is water soluble and very reactive. What is to prevent it from being leached out, or being washed into a sample? Besides calcium-40, the other daughter element in the potassium-40 decomposition process, is argon-40. This is the daughter element normally used for dating purposes. Argon is a gas that can easily escape into the atmosphere! If argon escapes into the air, then how will dates based upon its absence or presence be reliable? These and other sources of error make these radiometric systems entirely useless in the study of the age of the earth.
(These notes and quotes were extracted from The New Encyclopædia Britannica,
Chicago, 1989, vol. 19, macropædia section on Geochronology pp. 785-789)
Besides the theoretical problems, actual measurements usually give anomalous dates for rock samples. This phenomenon is well documented. In one example volcanic rocks, known to have formed in the last 200 years, gave the bizarre age of 3,000,000 years. Clearly radiometric dating methods are useless as instruments to estimate the age of the earth.
On the other hand there are evidences that certain radiometric processes would indicate a young age for the earth. For example, helium isotopes are a by-product of uranium and other natural radioactive decay. Assuming that 100% of the helium in the earth’s atmosphere is the by-product of radioactive decay, and assuming current rates, then the earth’s atmosphere can be no more than 40,000 years old.
Unlike other radiometric dating systems, carbon fourteen (14C ) dating has a demonstrated validity, but only for relatively recent events. The most optimistic of scientists would not extrapolate 14C dating validity beyond 40,000 years. It is highly accurate for several thousand years. The older the dates, the less their reliability. The same kinds of questions posed for the other radiometric dating systems apply here. What was the ratio of mother to daughter elements in the beginning? Have conditions remained constant? Has contamination occurred? Due to evolutionary bias about the age of the earth, 14C dating is not normally applied to date strata where other radiometric methods might be considered. However, it would be interesting to apply radiocarbon dating to coal and oil deposits, or to the dinosaur tissue recently discovered in China (see next post).
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