Geologic Dating Methods: Are They Always Accurate?

Geologists use radiometric dating methods to determine the age of strata and fossils. Are they always accurate? Does an evolutionary bias affect the dating?

When a new fossil is discovered, geologists assign a date for when they think the plant or animal lived. They normally use radiometric dating methods to date the fossil, and many promote these methods as being accurate. Yet when you look into the technical papers on these discoveries, you find that these dates are often questionable and are sometimes clearly in error.

What are radiometric dating methods?

Several types of radiometric dating methods are used today. One of the best known is carbon 14 (C-14). When a plant or animal dies, the carbon in it has a small amount of radioactivity. C-14 is produced when high-energy particles from solar radiation hit the earth’s atmosphere and make the unstable element called C-14. As time goes by, this C-14 slowly changes back to stable atoms. explains: “Carbon-14 dating, also called radiocarbon dating, [is a] method of age determination that depends upon the decay to nitrogen of radiocarbon (carbon-14). Carbon-14 is continually formed in nature by the interaction of neutrons with nitrogen-14 in the Earth’s atmosphere; the neutrons required for this reaction are produced by cosmic rays interacting with the atmosphere.

“Radiocarbon … is absorbed from the air by green plants and then passed on to animals through the food chain. Radiocarbon decays slowly in a living organism, and the amount lost is continually replenished as long as the organism takes in air or food. Once the organism dies, however, it ceases to absorb carbon-14, so that the amount of the radiocarbon in its tissues steadily decreases. Carbon-14 has a half-life of 5,730 ± 40 years—i.e., half the amount of the radioisotope present at any given time will undergo spontaneous disintegration during the succeeding 5,730 years. Because carbon-14 decays at this constant rate, an estimate of the date at which an organism died can be made by measuring the amount of its residual radiocarbon. …

“It has proved to be a versatile technique of dating fossils and archaeological specimens from 500 to 50,000 years old.”

There are also other radiometric dating methods that are used to date strata and fossils. One of the most common is the potassium-argon dating method. This is used to date volcanic rock to the time the volcano erupted. If this rock is above a fossil, that fossil can be dated as “older” than the volcanic rock above it.

Encarta 2006 Premium Encyclopedia’s article on “Archaeology” explains:

“Potassium-argon dating provides approximate dates for sites in early prehistory. Geologists use this method to date volcanic rocks that may be as much as 4 billion to 5 billion years old. Potassium is one of the most abundant elements in the earth’s crust. Many minerals contain radioactive K-40 (potassium 40) isotopes, which decay at a known rate into Ar-40 (argon 40) gas. Scientists use a device called a spectrometer to measure the accumulation of Ar-40 in relation to amounts of K-40. The ratio of these elements can indicate the age of a geologic layer, generally since it last underwent a metamorphosis, such as melting under the heat of molten lava from a volcanic eruption. Thus, geologic layers rich in volcanic deposits lend themselves to potassium-argon dating.”

Sometimes radiometric dating methods give results that are totally wrong. One example of this is the KNM-ER 1470 fossil found in Kenya by Bernard Ngeneo, a field worker for the famous paleoanthropologist Richard Leakey. When the original sample of the volcanic tuff was given to the laboratory, the potassium-argon date was about 230 million years. This date would mean that men lived during the time of the dinosaurs and would upset the evolutionary timescale. So new samples were sent and finally a date of 2.4 million years was eventually accepted (Nature 226, April 18, 1970, pp. 226-228).

Since evolutionary theory is generally assumed to be true, it is to be expected that dates that do not fit the evolutionary timescale will be reexamined or dismissed. But does this assumption lead to circular reasoning and wrong conclusions?Since evolutionary theory is generally assumed to be true, it is to be expected that dates that do not fit the evolutionary timescale will be reexamined or dismissed. But does this assumption lead to circular reasoning and wrong conclusions?

Assumptions of these methods

In order to calibrate these dates, geologists must use certain assumptions:

  1. The amount of the radioactive element at the time of origin is known.
  2. The rate of decay of the radioactive element is the same throughout time.
  3. There has been no contamination or loss of the radioactive element or the radioactive decay products since being formed in the sample.

Problems can occur when using these assumptions. The Bible shows that before the Flood in Genesis 7, conditions were different on the earth. Adam lived for 930 years. Clearly something was different during that period of time. Perhaps there were atmospheric differences that could have affected the amount of radioactive material produced at that time.

Scientists have to assume that C-14 production has been a constant in order to calibrate their dating methods. Yet it is known that the amount of C-14 in the atmosphere has changed over time, and the amount of C-14 in the atmosphere varies. The nuclear bomb tests of the 1950s, for example, actually changed the amount of radioactive carbon in the atmosphere.

Another problem with radiometric dating methods is the assumption about the amount of the original radioactive element. How do we know exactly how much potassium was originally in the volcanic rock? As we will see, this method clearly can give erroneous dates for strata.

Even the method used for dating a sample can lead to dramatic changes in dates for an item. National Geographic Magazine explained that a different dating method for C-14 indicated the oldest Maya civilization was not nearly as old as earlier data had indicated. The article states: “The remains of a woman found below a layered platform called Cuello in northern Belize had been thought to be more than 4,000 years old. … As a result of new dating methods, about a thousand years have been trimmed from the chronology” (“Oldest Known Maya: Not Quite So Old,” Nov. 8, 1990).

A thousand years is a very large error!

Radiometric dating methods are referred to as “absolute” dating, but that doesn’t mean the dates they arrive at are necessarily certain. Scientists use the term absolute to distinguish from relative dating methods. When fossil A is found in rock strata below a rock layer containing fossil B, fossil A can generally be dated as older, relative to fossil B. That is relative dating. But relative dating doesn’t yield actual age; that is what absolute dating attempts to do.

“Absolute dating complements relative dating by providing a specific (not necessarily precise) chronological age for a given specimen” (Glen Kuban, Introduction to Fossil Collecting, 1994-2000, emphasis added).

Yet many presume these dating methods are absolute in terms of certainty. This is misleading, since dates determined by radiometric dating methods are not always absolute at all.

Environmental conditions

Erroneous dates can occur when the environment has affected the sample. For example, the C-14 dates of living mollusks found in rivers can give anomalous dates.

In an article published in Science, M.L. Keith and G.M. Anderson discussed the results of their studies from the Meramec River in Missouri (“Radiocarbon Dating: Fictitious Results With Mollusk Shells,” Vol. 141, p. 634). They found that living freshwater mollusks give anomalous dates of up to 3,000 years old. This is caused by the absorption of C-14 from ancient plant remains in humus.

Here we find that the environment can seriously affect the amount of C-14 found in living creatures.

“Radiocarbon: Ages in Error,” an article by Robert E. Lee in the Anthropological Journal of Canada, said that artifacts found in the area of a volcano can give erroneous ages of up to 4,000 years. “Older carbon can be moved upward by circulating groundwater, to impregnate a young sample thereby diluting the carbon-14 in the sample—thus providing a date that is too old, a date that is false” (Vol. 19, 1981, p. 14).

Tree ring dating

Some scientists have used tree rings to attempt to prove that C-14 dating is accurate in dating items from thousands of years ago. Yet there are problems with this method also.

Tree rings are caused by the changes in growth rates during a calendar year. In their article “Past Climate Reconstructed From Tree Rings,” Harold Fritts, G. Robert Lofgren and Geoffrey Gordon explained, “In particularly unfavorable years, the rings are narrow, and in some trees no ring is formed at all. In other seasons an unusual period of drought during the growing season may cause some trees to produce more than one ring for that year” (Climate and History: Studies in Interdisciplinary History, 1981, p. 195).

Frederic Jueneman discussed this problem in an article in Industrial Research (August 1972, p. 13). Discussing the problems of C-14 dates, he wrote: “Strange anomalies were found in dating of the tree rings progressively worsening earlier than the year—1500 [1500 B.C.]. There were many more years of tree rings than radiocarbon dating gave credit for.” He explained that artificial adjustments were later made to the C-14 dating method that made them appear to be accurate.

The simple answer to the problem is that more than one ring can be made when there is a drought.

Egyptian dating problems

In his book Pharaohs and Kings, David Rohl explained that C-14 dating is not always accurate: “It is not generally appreciated but a number of historians of a conventional persuasion are similarly troubled by the radiocarbon data applied to archaeological samples. … They often resort to extreme measures to deal with the dating conflicts which arise” (1996, p. 384).

The book goes on to explain that the tree ring dating could be part of the problem. Also there is a 45-percent rejection rate when C-14 dates are taken from various samples. How do you know which dates are correct? Scientists have biases as everyone does. They will reject dates that don’t agree with their own ideas about history and Egyptian chronology. The article contains a chart showing how dates for Egyptian kings are hundreds of years off during the first and second millennium B.C. when compared to conventional historical dates.

Rohl wrote, “Israeli archaeologist A Mazar refuses to use C-14 dating for Palestinian archaeological remains of the fourth and third millennium B.C.” (p. 385). Rohl showed that dendrochronology (tree ring dating) has been shown to be in error (p. 388).

Hawaiian lava flows

The Journal of Geophysical Research had an article by Juan Funkhouser and John Naughton discussing the erroneous dates given for the Hualalai Volcano in Hawaii. The date of the eruption is known to be around 1800-1801. Samples of the radiogenic argon give incorrect values. If the date of the eruption were not known, it would be assumed that the volcano erupted millions of years ago.

“Even taking into account the uncertainties of the analytical data, there is a definite excess of radiogenic argon and helium present, particularly evident for samples of historic age” (“Radiogenic Helium and Argon in Ultramafic Inclusions From Hawaii,” Vol. 73, Issue 14, July 15, 1968, p. 4602).

There are many articles from scientific journals that show the discrepancies in the radiometric dating methods. When a date doesn’t coincide with the ideas of evolution, the date is generally reexamined or reconsidered. Later the problem becomes buried and forgotten by most scientists.

Are all dates determined by geologic dating methods wrong? No. But when various methods give conflicting dates, care should be taken. Clearly, the environment can affect radiometric dates and cause a gross misinterpretation of history.

New evidence can turn up at any time and overturn assumptions that have been made for many years. When radiometric dates seem to contradict biblical events, keep in mind that these dates can be wrong. Be sure to read the articles on evolution and creation on this Life, Hope & Truth site, starting with “Intelligent Design: Can Science Answer the Question, Does God Exist?

About the Author

Bill Jahns

Bill Jahns

Bill Jahns graduated from Ambassador College in 1969, and he has worked full time in the ministry since then. Presently, he serves with the Church of God, a Worldwide Association, pastoring congregations in Morgantown, West Virginia, and Athens-Parkersburg, Ohio.

Read More

Get the Latest

InSights Blog

Get the latest blog posts from Life, Hope & Truth straight to your inbox.


Never miss a post! Sign up to receive the week's latest articles, blog posts and updates.



Discern is published every two months and is available in digital and print versions. Choose your preferred format to start your subscription.

Print subscriptions available in U.S., Canada and Europe


Please choose your region: