In Part two of this series we discussed radiocarbon dating as a method used to identify the age of organic materials.  We will now take a much more in-depth look at the various dating methods in an effort to determine their usefulness in establishing the age of rocks and fossils found in the geologic record. 

       Dating methods used to arrive at the age of rocks and fossils is a critical issue in the whole creation/evolution controversy.


       Scientists believe the radiometric dating techniques in current use accurately identify the age of the earth as approximately four and one-half billion years old.  Radiometric dating is the process of determining the age of rocks from the decay of their radioactive elements.  This dating method has been in widespread use for over half a century. There are over forty such techniques, each using a different radioactive element or a different way of measuring them.  Scientists claim these radiometric dating techniques agree with each other as a whole and, therefore, present a coherent picture in establishing a very old age for the Earth and universe. 

       Rocks are made up of many individual crystals, and each crystal is usually made up of at least several different chemical elements such as iron, magnesium, silicon, etc. Most of the elements in nature are stable and do not change. However, some elements are not completely stable in their natural state. Some of the atoms eventually change from one element to another by a process called radioactive decay. Atoms of the original element, called the parent element, decay to atoms of another element, called the daughter element, at a predictable rate. The passage of time can be charted by the reduction in the number of parent atoms, and the increase in the number of daughter atoms.

       A rock that is to be dated must be free from the loss or the addition of additional radioactive parent atoms or daughter atoms from the time the rock was made. If it has lost some of the daughter element or if it has gained additional parent element, it would change the decay rate and result in an inaccurate determination of age.  Scientists believe most dating techniques have very good ways of telling if such a loss or gain has occurred and if it has occurred, the date is thrown out.

       Scientists report that radioactive elements used in radiometric dating have been subjected to heat, cold, pressure, vacuum, acceleration, and strong chemical reactions in various laboratory testing.  The purpose of these tests is to expose these elements to the same kind of environmental dynamics that would be experienced by rocks or magma in nature.  Based on such tests, scientists have concluded that decay rates are unaffected by such forces of nature.  Therefore, it is believed the amount of radioactive atoms found in rock remains stable from the time the rock was formed with no additional such atoms being added.  It is claimed that in only a couple of special cases have any decay rates been observed to vary and none of these special cases appy to the dating of rocks.


       Observation of how radioactive elements change from one form to another has shown that such change occurs in half-lives.  If it takes a certain length of time for half of the atoms to decay, it will take the same amount of time for half of the remaining atoms, or a fourth of the original total, to decay. In the next interval, with only a fourth remaining, only one eighth of the original total will decay. By the time ten of these intervals, or half-lives, have passed, less than one thousandth of the original number of radioactive atoms is left. The amount of decay from a fixed number of radioactive atoms decreases as there are fewer atoms left to decay.  

       The various radiometric dating techniques are all based on measurement of a different radioactive isotope. An isotope is a subdivided group of atoms of a particular element. For example, the element uranium has three isotopes (subdivisions), U-235, U-238 and U-239.  Each isotope has a different atomic weight represented by a different number.  The element carbon has isotopes of 12, 13 and 14.  Only the carbon 14 isotope is radioactive and therefore only this isotope is used in carbon 14 dating.  Carbon-14 has a half-life of 5,715 years.  In 5,715 years, one-half of a given amount of carbon-14 turns to the element nitrogen-14.  Uranium-238 has a half-life of 4.5 billion years after which one-half of it becomes the element lead-206.  Thorium-230 has a half-live of 75,400 years after which one-half of it becomes radium-226.  Potassium-40 is a radioactive isotope having a 1.26 billion year half life at which time half of it turns into the isotope argon-40.

       Eighty-four elements having 339 isotopes occur naturally in nature.  Two-hundred and sixty-nine isotopes are stable and 70 are radioactive.  Eighteen of the radioactive isotopes have long half-lives and are the ones usually used in radiometric dating.  Half-lives are measured directly either by using a radiation detector to count the number of atoms decaying in a given amount of time from a known amount of the parent material, or by measuring the ratio of daughter to parent atoms in a sample that originally consisted completely of parent atoms. 


       Igneous rock is formed when hot lava from a volcano cools and hardens.  This hardening results in radioactive isotopes of minerals that make up the rock to remain stationary in the rock.  As the radioactive isotope begins to decay, it forms atoms of a daughter element.  The age of the rock is determined by first measuring the number of daughter atoms and the number of remaining parent atoms and then calculating the ratio between them. Then the half-life is used to calculate the time it took to produce that ratio of parent atoms to daughter atoms.

       There is one major complication to this process and that is determining whether or not there were atoms of the daughter element already present in the rock.  The presence of such preexisting daughter elements would invalidate any age determination of the rock based on radiometric dating.  Let’s use potassium as an example.  Potassium is a common mineral found in igneous rock.  One isotope of this mineral is radioactive potassium-40. This isotope decays into 88.8% calcium-40 and 11.2% argon-40.  It is difficult to determine how much calcium-40 is initially present in rocks being dated.  So the potassium-40 to calcium-40 ratio is not often used.

       On the other hand, argon is a gas.  When lava is still in its molten state, the argon readily escapes.  Once the lava hardens, it begins to trap additional argon being produced by the decay of potassium-40.  You, therefore, begin with newly formed argon atoms which can be measured against the number of potassium-40 atoms and arrive at an age for the rock. In reality, however, there is often a small amount of argon remaining in a rock when it hardens. This argon is absorbed from the air and is usually trapped in the form of very tiny air bubbles in the rock.  This non-radioactively formed argon must be accounted for in order to accurately determine the age of a rock. This is accomplished in the following manner:  Argon has an isotope of its own called argon-36. The ratio of argon-40 to argon-36 in air is well known, at 295. Thus, if one measures argon-36 as well as argon-40, one can calculate and subtract off the air-argon-40 to get an accurate age of the rock.


       Some have challenged the potassium-argon method of dating by showing that some igneous rocks dated by this method have been shown to be several million years old when in fact such rocks have been formed in just the past few years. Geologists respond that potassium-40, with its long half life of 1.26 billion years, is not intended to date young rocks. To try to do so is to improperly use this method.  The argon-40 found in such rocks has not been produced by decay of potassium-40 but was in the rock to begin with.  When such argon-40 atoms are compared to potassium -40 atoms which have not come close to their half-life of decay, you would expect to get a false reading because you are comparing a daughter isotope to a parent isotope that has not yet produced any daughter.  To further verify potassium/argon dating results, scientists will use the argon/argon method which involves using a nuclear reactor and incremental heating of the rock to produce isotopic argon by-products that, when measured, provide validation of the potassium/argon dating of a particular rock.

      In nearly all radiometric dating methods, except potassium-argon and the associated argon-argon method, there is always some amount of the daughter product already in the rock when it cools.  Critics of radiometric dating believe this to be a major obstacle to accurate dating.  Such critics believe that a rock cannot remain free of daughter materials through millions of years of exposure to other rocks, water, chemicals, changes in radiation, etc.  It is further believed that just one major catastrophe, such as the Noachian flood, would have produced massive mixing of parent and daughter materials in rocks.

       Geologists don’t deny the existence of daughter materials unrelated to the decay of radioactive isotopes in rocks they date. They believe, however, that they have dependable methods of precisely determining how much of the daughter product was already in the rock when it cooled and hardened.  Geologists will often use several dating methods on the same rock to verify its age.  When several dating methods produce the same result, it is felt that the age of a rock has been properly identified. Geologists have also examined moon rocks and meteorites and have found them to be the same age as that of the oldest earth rocks. Rocks obtained from the moon would not be exposed to the kind of environmental factors some creationists believe have negatively affected the accuracy of radiometric dating of earth rocks.   

       Some creationists charge that decay rates of radioactive material have not been constant throughout time.  They cite the work of H.C. Dudley who claims to have changed the decay rates of 14 different radioactive isotopes by means of pressure, temperature, electric and magnetic fields and other methods. I have contacted several creationist organizations and the Library of Congress in an effort to locate the original work of H.C. Dudley.  I have not been able to locate his work so I can’t examine and verify his claims.

       Scientists respond to the charge that decay rates have not been constant by pointing out that telescopes allow us to see supernovae (exploding stars) at distances so vast that the pictures take hundreds of thousands to millions of years to arrive at the Earth. So the events we see today actually occurred hundreds of thousands to millions of years ago. Scientists have found that much of the light following a supernova blast is powered by newly created radioactive parents. Therefore, radiometric decay in the supernova light is able to be measured. These half-lives completely agree with the half-lives measured from decays occurring today. Scientists have concluded that all evidence points towards unchanging radioactive half-lives.

       As briefly discussed in part two of this series, some creationists believe the atmosphere above the earth at one time contained much more water than at present.  It is felt this vapor canopy greatly altered the degree of cosmic radiation hitting the earth and thus altered the radioactive isotope content of rocks.  Geologists point out that moon and meteorite rocks show the same radioactive isotopes as earth rocks and therefore the canopy theory is a mute point. 

       Creationists point to the Van Allen radiation belt which encircles the earth at a distance of about 450 miles. The belt emits very intense radiation. It is believed that any change over time in the level of emissions from this belt would alter the decay rate of radioactive minerals.  Scientists respond that there is no evidence to show this rate has changed over time and again point out that measurement of decay rates of radioactive isotopes found in light from ancient exploding stars demonstrates the consistency of decay rates over time.

       In an attempt to coordinate radiometric findings with belief in a young earth, some creationists have advanced the idea of the earth having an apparent old age.  If God created the earth in six days, rocks, plants, animals and man would have been created whole and fully grown. Therefore all radioactive minerals would be already partially through their half-lives on the day they were created. Since there is no way of testing this idea, it remains nothing more than an attempt to explain the conclusions of radiometric dating within the framework of assigning young earth conclusions to the Genesis account.


       The earths crust is largely made up of igneous rock which is cooled-downed liquid rock called magma or lava.  Overlaying much of igneous rock is sedimentary rock.  Sedimentary rock is made from the accumulation of various sized particles of various types of rock.  This rock is usually laid down in layers called strata as a result of the action of water. Radioactive mineral isotopes that are found in sedimentary rock are derived from the weathering of igneous rocks.  Radiometric dating of such isotopes found in sedimentary rock does not date the sedimentary rock as such but only the bits of igneous rock found in the sedimentary rock.  Therefore, with the exception of carbon-14 dating, radiometric dating cannot be used to establish the age of sedimentary rock or the fossils found in them.  

       Fossils are largely the mineralization of once existing organic material and contain carbon, including carbon-14. Therefore, carbon-14 dating is used to date fossils and by association establish the age of the sedimentary rock. Another way sedimentary rocks and the fossils found in them are dated is to use radiometric dating information on igneous rocks found below and above sedimentary rocks.  By determining the age of such igneous rock found above and below sedimentary rock and then using carbon-14 dating to date the fossils in such sedimentary rock, it is felt a reasonably accurate age can be determined for the fossils and the sedimentary rock in which they are found.  

       Critics of this method of dating sedimentary rock, and the fossils they contain, point out that in many cases the carbon-14 dates don’t correlate well with the dates determined for the igneous rock surrounding the sedimentary strata.  It’s pointed out that the geologic record sometimes shows both older and younger igneous rock found above and sometimes below sedimentary rock in the same area.  It is therefore believed that this method of dating sedimentary rock and its fossils is highly problematic.  It is further pointed out that since fossils of greater and lesser complexity are found scattered throughout sedimentary strata, there is no basis upon which to date some fossils as older than others.   

      Evolutionists, having recognized this problem even before radiometric dating was developed, established a method of dating called indexing. Indexing is a method of identifying a greater number of certain types of fossils within a certain level of strata and assigning a date to those fossils based on what is felt to be their level of complexity as compared to other fossils. All fossils in those particular strata are then assigned that same age and subsequently, the sedimentary strata in which the fossils are found are given the same age.  It is from this approach that the geological columns indicating long ages of geological time were developed.  This dating method assumes life evolved from simple to complex forms.  Evolutionists believe that carbon-14 dating of fossils has confirmed their previous assumptions of organic development from simple to complex.  They believe radiometric dating of igneous rock surrounding the sedimentary strata has been consistent enough with carbon-14 dating of fossils to establish valid dating of the sedimentary strata in which the fossils are found and also establish the validity of the earth and its fossils being billions of years old.

       Creationists see indexing as circular reasoning where an assumed age of fossils is used to date strata and strata are then used to date the fossils. It is pointed out that indexing doesn’t account for the presence of fossils found in a particular strata that are quite different in complexity from the index fossils.  It is further pointed out that so-called simple fossils are often found to have very complex structures and therefore cannot be defined as simple.  It is felt that since fossils of all types are found throughout the sedimentary strata, indexing is of little value in identifying progression of simple to complex.  It is also believed that the appearance of younger and older igneous rock both above and below the same area of sedimentary rock is a significant challenge to using radiometric dating to date fossils and establish the age of sedimentary strata.  When these observations are combined with what is felt to be serious problems with radiometric dating in general, young earth creationists see the determination of the earth being billions of years old as untenable.    


       Evolutionists believe sedimentary strata has been gradually laid down over millions of years due to uniformitarian processes involving the action of water and its effects on igneous and other types of rock that make up the earths crust.  Living organisms, including plant life, are believed to have slowly developed during these same long periods of time and some of their remains were trapped in developing sedimentary rock due to floods, volcanoes, earthquakes or just plain settling of sediment occurring over these long periods of time.  Evolutionary geologists see much strata being laid down vertically in horizontal layers, one layer at a time, due to slow sorting and settling of sediment contained in slow moving water. Because of the great amount of strata found on the earth, including such geologic wonders as the Grand Canyon, it is believed that it has taken millions of years for these strata to develop.   

      Because it is believed much strata has been laid down horizontally, one layer upon another in a slow methodical fashion over millions of years, younger strata are believed to overlay older strata with the oldest strata being lower in the geological column and more recently formed strata being found at the top of the column.

       Both evolutionary geologists and old earth creationist geologists believe the strata have been laid down over millions of years. For young earth creationists, the Noachian flood is seen as providing the right conditions for the development of the stratification of sedimentary rock seen throughout the world.  Young earth creationists point to the work of French sedimentologist Guy Berthault who has demonstrated in the laboratory how strata can develop vertically to produce horizontal layers in a very short period of time. Therefore, horizontal layers can be all the same age and not thousands or millions of years apart in age.  Berthault produced different currents of water running over and through particles of sediment in a tank designed for his experiments.  What he observed is that the action of moving water over and through sediment moved the sediment sideways producing vertical layers of horizontal sediment and stratified according to the density of the particles. For details about the research of Guy Berthault go to: www.answersingenesis.org/tj/v11/i1/sedimentation_reply.asp

       What these experiments show is that multiple horizontal levels of sedimentary rock can form rapidly and simultaneously, due to a current of water pushing and shorting particles along an upward vertical path.  This same mechanism is seen at work along shorelines around the world.  In an experiment in Queensland Australia, a sand slurry made up of 30% sand and 70% water, was pumped at a rate of 100.000 gallons per minute. This resulted in the disposition of layers of material four to five feet high and the width of a football field.

       For many creationists, this research tells them that the strata containing fossils could have been formed over much shorter periods of time than postulated by evolutionists.  To the young age creationist, this shorter period of time could very easily be the past six to twelve thousand years with much of the geologic stratification that is seen caused by the catastrophic action of the Noachian flood.

       Creationists point to the expulsion of Mount St. Helens in 1980 as an example of how a catastrophic event can change the topography of the land in a very short time.  On May 18, 1980, Mt. St. Helens erupted and in eight minutes 230 square miles of forest was destroyed.  In nine hours the top quarter and entire center of the mountain disappeared, leaving a vast, horseshoe shaped hole.  Two hundred and fifty feet of material was deposited in Spirit Lake located near the base of the mountain.  In short time canyons were formed by the rapid flow of volcanic ash and hot mud.

       In the months and years following this explosion, thousands of upright trees can be seen at all different levels of developing layers of sediment in Spirit Lake. If Spirit Lake were to recede and the sediment dry out and become layered sedimentary rock, an evolutionary geologist, who wasn’t aware of the Mt. St. Helens event, could look at the upright trees at different horizontal levels and conclude that such stratification was the result of millions of years of uniformitarian development when in fact such stratification of sedimentary deposits has developed in a short number of years due to the catastrophic explosion of Mt. St. Helens.

       Creationists believe such rapid change as produced by the Mt. St. Helens volcano and the findings of the Berthault experiments, have significant ramifications relative to the dating of sedimentary rock and the fossils found in such rock. If flow of water can form a vertical buildup of horizontal stratification of sediment in a short period of time, then such layers of sedimentary stratification would be all the same age.  If the strata are the same age, then the fossils found within such strata would also be the same age.  This is seen as having serious implications relative to the validity of the geologic column and the dating methods used to establish long time frames for the development of organic material and the strata in which such organic material is found.

       Evolutionists counter that there are many places in the world where strata appear to have been laid down under undisturbed conditions with no evidence of catastrophism. Even where strata is found turned upside down from its presumed vertical order of older at the bottom to younger at the top, such strata is seen with the exact reverse order of oldest layers on top and youngest layers on the bottom.  Such upside down strata is believed to result from land being  "faulted" or "bent" as a result of volcano’s, earthquakes and other disturbances. Evolutionists point out that such reversed strata still remain in the assumed relative order, only in reverse and such cases of "out of order strata" are not found in large flat undisturbed basins, as many deep core drilling's of regions round the world have demonstrated.  It is further pointed out that even where the geologic order is interrupted, the relative layers remain the same as originally predicted by the geologic column.

       Evolutionists point out that you can’t necessarily equate the sudden creation of canyons and sediment by the rapid flow of volcanic material with the creation of the Grand Canyon and other canyons that have been formed by the erosion of sedimentary rock made up of limestone, sandstone, and shale.  They point out that many of the sedimentary strata in and around the Grand Canyon contain the tracks of animals. The red Kayenta formation, near Glen Canyon Dam, contains the tracks of dinosaurs. Evolutionists ask young earth creationists why animals would have been walking around at various strata levels if indeed these strata were all laid down at the same time due to a catastrophic event such as the Noachian flood.

       While evolutionists acknowledge the work of Berthault as contributing to our understanding of how strata can form, they reject the idea that it has to form in this manner.  Evolutionists point to Lake Suigetsu in Japan which has had many of its 45 thousand layers individually carbon-dated, and each layer, as you go from top to bottom, was found to be older than the one above by approximately one year, going back 45 thousand years.  It is discoveries such as this that evolutionary geologists feel provide strong evidence for taking a more uniformitarian approach to establishing the age of the earth

       Evolutionists point out that they do not reject catastrophism as occurring and being responsible for some of the geologic record.  They do not, however, see such catastrophism as pointing to a young earth as this flies in the face of what thy consider proven dating methods that show an old earth and the gradual development of life forms.

       In our next installment in this series, we will examine  evidence for how the geologic record may have been formed due to a catastrophic event such as the Noachian flood.