Does Radiometric Dating Prove the Earth Is Old?

The presupposition of long ages is an icon and foundational to the evolutionary model. Nearly every textbook and media journal teaches that the earth is billions of years old.

Using radioactive dating, scientists have determined that the Earth is about 4.5 billion years old, ancient enough for all species to have been formed through evolution.1

The earth is now regarded as between 4.5 and 4.6 billion years old.2

The primary dating method scientists use for determining the age of the earth is radioisotope dating. Proponents of evolution publicize radioisotope dating as a reliable and consistent method for obtaining absolute ages of rocks and the age of the earth. This apparent consistency in textbooks and the media has convinced many Christians to accept an old earth (4.6 billion years old).

What Is Radioisotope Dating?

Radioisotope dating (also referred to as radiometric dating) is the process of estimating the age of rocks from the decay of their radioactive elements. There are certain kinds of atoms in nature that are unstable and spontaneously change (decay) into other kinds of atoms. For example, uranium will radioactively decay through a series of steps until it becomes the stable element lead. Likewise, potassium decays into the element argon. The original element is referred to as the parent element (in these cases uranium and potassium), and the end result is called the daughter element (lead and argon).

The Importance of Radioisotope Dating

The straightforward reading of Scripture reveals that the days of creation (Genesis 1) were literal days and that the earth is just thousands of years old and not billions. There appears to be a fundamental conflict between the Bible and the reported ages given by radioisotope dating. Since God is the Creator of all things (including science), and His Word is true (“Sanctify them by Your truth. Your word is truth,” John 17:17), the true age of the earth must agree with His Word. However, rather than accept the biblical account of creation, many Christians have accepted the radioisotope dates of billions of years and attempted to fit long ages into the Bible. The implications of doing this are profound and affect many parts of the Bible.

How Radioisotope Dating Works

Radioisotope dating is commonly used to date igneous rocks. These are rocks which form when hot, molten material cools and solidifies. Types of igneous rocks include granite and basalt (lava). Sedimentary rocks, which contain most of the world’s fossils, are not commonly used in radioisotope dating. These types of rocks are comprised of particles from many preexisting rocks which were transported (mostly by water) and redeposited somewhere else. Types of sedimentary rocks include sandstone, shale, and limestone.

The radioisotope dating clock starts when a rock cools. During the molten state it is assumed that the intense heat will force any gaseous daughter elements like argon to escape. Once the rock cools it is assumed that no more atoms can escape and any daughter element found in a rock will be the result of radioactive decay. The dating process then requires measuring how much daughter element is in a rock sample and knowing the decay rate (i.e., how long it takes the parent element to decay into the daughter element—uranium into lead or potassium into argon). The decay rate is measured in terms of half-life. Half-life is defined as the length of time it takes half of the remaining atoms of a radioactive parent element to decay. For example, the remaining radioactive parent material will decrease by 1/2 during the passage of each half-life (1→1/2→1/4→1/8→1/16, etc.). Half-lives as measured today are very accurate, even the extremely slow half-lives. That is, billion-year half-lives can be measured statistically in just hours of time. The following table is a sample of different element half-lives.

Science and Assumptions

Scientists use observational science to measure the amount of a daughter element within a rock sample and to determine the present observable decay rate of the parent element. Dating methods must also rely on another kind of science called historical science. Historical science cannot be observed. Determining the conditions present when a rock first formed can only be studied through historical science. Determining how the environment might have affected a rock also falls under historical science. Neither condition is directly observable. Since radioisotope dating uses both types of science, we can’t directly measure the age of something. We can use scientific techniques in the present, combined with assumptions about historical events, to estimate the age. Therefore, there are several assumptions that must be made in radioisotope dating. Three critical assumptions can affect the results during radioisotope dating:

1. The initial conditions of the rock sample are accurately known.
2. The amount of parent or daughter elements in a sample has not been altered by processes other than radioactive decay.
3. The decay rate (or half-life) of the parent isotope has remained constant since the rock was formed.

The Hourglass Illustration

Radioisotope dating can be better understood using an illustration with an hourglass. If we walk into a room and observe an hourglass with sand at the top and sand at the bottom, we could calculate how long the hourglass has been running. By estimating how fast the sand is falling and measuring the amount of sand at the bottom, we could calculate how much time has elapsed since the hourglass was turned over. All our calculations could be correct (observational science), but the result could be wrong. This is because we failed to take into account some critical assumptions.

1. Was there any sand at the bottom when the hourglass was first turned over (initial conditions)?
2. Has any sand been added or taken out of the hourglass? (Unlike the open-system nature of a rock, this is not possible for a sealed hourglass.)
3. Has the sand always been falling at a constant rate?

Since we did not observe the initial conditions when the hourglass time started, we must make assumptions. All three of these assumptions can affect our time calculations. If scientists fail to consider each of these three critical assumptions, then radioisotope dating can give incorrect ages.

The Facts

We know that radioisotope dating does not always work because we can test it on rocks of known age. In 1997, a team of eight research scientists known as the RATE group (Radioisotopes and the Age of The Earth) set out to investigate the assumptions commonly made in standard radioisotope dating practices (also referred to as single-sample radioisotope dating). Their findings were significant and directly impact the evolutionary dates of millions of years.3

A rock sample from the newly formed 1986 lava dome from Mount St. Helens was dated using Potassium-Argon dating. The newly formed rock gave ages for the different minerals in it of between 0.5 and 2.8 million years.4 These dates show that significant argon (daughter element) was present when the rock solidified (assumption 1 is false).

Mount Ngauruhoe is located on the North Island of New Zealand and is one of the country’s most active volcanoes. Eleven samples were taken from solidified lava and dated. These rocks are known to have formed from eruptions in 1949, 1954, and 1975. The rock samples were sent to a respected commercial laboratory (Geochron Laboratories in Cambridge, Massachusetts). The “ages” of the rocks ranged from 0.27 to 3.5 million years old.5 Because these rocks are known to be less than 70 years old, it is apparent that assumption #1 is again false. When radioisotope dating fails to give accurate dates on rocks of known age, why should we trust it for rocks of unknown age? In each case the ages of the rocks were greatly inflated.

Isochron Dating

There is another form of dating called isochron dating, which involves analyzing four or more samples from the same rock unit. This form of dating attempts to eliminate one of the assumptions in single-sample radioisotope dating by using ratios and graphs rather than counting atoms present. It does not depend on the initial concentration of the daughter element being zero. The isochron dating technique is thought to be infallible because it supposedly eliminates the assumptions about starting conditions. However, this method has different assumptions about starting conditions and can give incorrect dates.

If single-sample and isochron dating methods are objective and reliable they should agree. However, they frequently do not. When a rock is dated by more than one method it may yield very different ages. For example, the RATE group obtained radioisotope dates from ten different locations. To omit any potential bias, the rock samples were analyzed by several commercial laboratories. In each case, the isochron dates differed substantially from the single-sample radioisotope dates. In some cases the range was more than 500 million years.6 Two conclusions drawn by the RATE group include:

1. The single-sample potassium-argon dates showed a wide variation.
2. A marked variation in ages was found in the isochron method using different parent-daughter analyses.

If different methods yield different ages and there are variations with the same method, how can scientists know for sure the age of any rock or the age of the earth?

In one specific case, samples were taken from the Cardenas Basalt, which is among the oldest strata in the eastern Grand Canyon. Next, samples from the western Canyon basalt lava flows, which are among the youngest formations in the canyon, were analyzed. Using the rubidium-strontium isochron dating method, an age of 1.11 billion years was assigned to the oldest rocks and a date of 1.14 billion years to the youngest lava flows. The youngest rocks gave a billion year age the same as the oldest rocks! Are the dates given in textbooks and journals accurate and objective? When assumptions are taken into consideration and discordant (disagreeing or unacceptable) dates are not omitted, radioisotope dating often gives inconsistent and inflated ages.

Two Case Studies

The RATE team selected two locations to collect rock samples to conduct analyses using multiple radioisotope dating methods. Both sites are understood by geologists to date from the Precambrian (supposedly 541–4,600 million years ago). The two sites chosen were the Beartooth Mountains of northwest Wyoming near Yellowstone National Park, and the Bass Rapids sill in the central portion of Arizona’s Grand Canyon. All rock samples (whole rock and separate minerals within the rock) were analyzed using four radioisotope methods. These included the isotopes potassium-argon (K-Ar), rubidium-strontium (Rb-Sr), samarium-neodymium (Sm-Nd), and lead-lead (Pb-Pb). In order to avoid any bias, the dating procedures were contracted out to commercial laboratories located in Colorado, Massachusetts, and Ontario, Canada.

In order to have a level of confidence in dating, different radioisotope methods used to date a rock sample should closely coincide in age. When this occurs, the sample ages are said to be concordant. In contrast, if multiple results for a rock disagree with each other in age they are said to be discordant.

Beartooth Mountains Sample Results

Geologists believe the Bearthooth Mountains rock unit to contain some of the oldest rocks in the United States, with an estimated age of 2,790 million years. The following table summarizes the RATE results.7

The results show a significant scatter in the ages for the various minerals and also between the isotope methods. In some cases, the whole rock age is greater than the age of the minerals, and for others, the reverse occurs. The potassium-argon mineral results vary between 1,520 and 2,620 million years (a difference of 1,100 million years).

Bass Rapids Sill Sample Results

The 11 Grand Canyon rock samples were also dated commercially using the most advanced radioisotope technology. The generally accepted age for this formation is 1,070 million years. The RATE results are summarized in the following table.8

The RATE results differ considerably from the generally accepted age of 1,070 million years. Especially noteworthy is the multiple whole rocks potassium-argon isochron age of 841.5 million years while the samarium-neodymium isochron gives 1,379 million years (a difference of 537.5 million years).

Possible Explanations for the Discordance

There are three possible explanations for the discordant isotope dates.

1. There may be a mixing of isotopes between the volcanic flow and the rock body into which the lava intrudes. There are ways to determine if this has occurred and can be eliminated as a possible explanation.
2. Some of the minerals may have solidified at different times. However, there is no evidence that lava cools and solidifies in the same place at such an incredibly slow pace. Therefore this explanation can be eliminated.
3. The decay rates have been different in the past than they are today. The following section will show that this provides the best explanation for the discordant ages.

New Studies

New studies by the RATE group have provided evidence that radioactive decay supports a young earth. One of their studies involved the amount of helium found in granite rocks. Granite contains tiny zircon crystals, which contain radioactive uranium (²³⁸U), which decays into lead (²⁰⁶Pb). During this process, for each atom of ²³⁸U decaying into ²⁰⁶Pb, eight helium atoms are formed and migrate out of the zircons and granite rapidly.

Within the zircon9 crystals, any helium atoms generated by nuclear decay in the distant past should have long ago migrated outward and escaped from these crystals. One would expect the helium gas to eventually diffuse upward out of the ground and then disappear into the atmosphere. To everyone’s surprise, however, large amounts of helium have been found trapped inside zircons.10

The decay of ²³⁸U into lead is a slow process (half-life of 4.5 billion years). Since helium migrates out of rocks rapidly, there should be very little to no helium remaining in the zircon crystals.

Why is so much helium still in the granite? One likely explanation is that sometime in the past the radioactive decay rate was greatly accelerated. The decay rate was accelerated so much that helium was being produced faster than it could have escaped, causing an abundant amount of helium to remain in the granite. The RATE group has gathered evidence that at some time in history nuclear decay was greatly accelerated.

The experiments the RATE project commissioned have clearly confirmed the numerical predictions of our Creation model.... The data and our analysis show that over a billion years worth of nuclear decay has occurred very recently, between 4000 and 8000 years ago.11

Confirmation of this accelerated nuclear decay having occurred is provided by adjacent uranium and polonium radiohalos that formed at the same time in the same biotite flakes in granites.12 Radiohalos result from the physical damage caused by radioactive decay of uranium and intermediate daughter atoms of polonium, so they are observable evidence that a lot of radioactive decay has occurred during the earth’s history. However, because the daughter polonium atoms are only short-lived (for example, polonium-218 decays within 3 minutes, compared to 4.47 million years for uranium-238), the polonium radiohalos had to form within hours to a few days. But in order to supply the needed polonium atoms to produce these polonium radiohalos within that timeframe, the nearby uranium atoms had to decay at an accelerated rate. Thus hundreds of millions of years worth of uranium decay (compared to today’s slow decay rate) had to have occurred within hours to a few days to produce these adjacent uranium and polonium radiohalos in granites.

The RATE group suggested that this accelerated decay took place during the Creation Week or during the Flood. Accelerated decay of this magnitude would result in immense amounts of heat being generated in rocks. Determining how this heat was dissipated presents a new and exciting opportunity for creation research.

Conclusion

The best way to learn about history and the age of the earth is to consult the history book of the universe—the Bible. Many scientists and theologians accept a straightforward reading of Scripture and agree that the earth is about 6,000 years old. It is better to use the infallible Word of God for our scientific assumptions than to change His Word in order to compromise with “science” that is based upon man’s fallible assumptions. True science will always support God’s Word.

Based on the measured helium retention, a statistical analysis gives an estimated age for the zircons of 6,000 ± 2,000 years. This age agrees with literal biblical history and is about 250,000 times shorter than the conventional age of 1.5 billion years for zircons. The conclusion is that helium diffusion data strongly supports the young-earth view of history.13

It must also be concluded, therefore, that because nuclear decay has been shown to have occurred at grossly accelerated rates when molten rocks were forming, crystallizing and cooling, the radiometric methods cannot possibly date these rocks accurately based on the false assumption of constant decay through earth history at today’s slow rates. Thus the radiometric dating methods are highly unreliable and don’t prove the earth is old.