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Radiometric Dating

Many people find it hard to understand how we can be critical of actual observations made on once molten rock. How can we argue with numbers? We must remember however that the rocks do not come with labels informing us of their ages. What the machines do tell us is a ratio of parent radioactive element to stable daughter element. It is up to us to figure out the significance of the values obtained from any given measurement. Sedimentary rocks are not dated in this way but just rocks which were once melted. It is assumed that the melting process eliminates all radioactive elements so that the process of radioactive decay starts at the point of solidifying. It is nevertheless true that many of the measurements on rocks do lead to calculations of very long ages. One potential use of these calculations is to provide an indication of what rocks lie lower than others in the rock column. But we do not want to take the numbers too seriously.

Dr. Steven Austin reviews the equations and the assumptions that go into the calculation of the age of a rock from the ratio or parent and daughter minerals. (Grand Canyon: Monument to Catastrophe. 1994. See chapter 6). The whole issue boils down to how much daughter element was present at time = 0. There are not a lot of cases where we can check the necessary assumptions, but Dr. Austin published one in 1996. In June of 1992 he collected a seven-kilogram sample of rock from the talus dome inside Mount St. Helens. From the position of the rock on the dome, the sample probably came from one of the last lava flows following the eruption of 1980. This particular flow was probably from 1986. The sample was sent away to a company which specialized in radiometric dating. Potassium-argon dates for various parts of the sample came back with ages ranging from 340,000 years to 2.8 million years. But we know that these rocks were less than ten years old!  Obviously, the molten lava did not eliminate all the argon before the rock solidified. And this is the problem with the dating method: not knowing how much daughter was initially present. [Steven A. Austin. 1996. Excess Argon within Mineral Concentrates from the New Dacite Lava Dome at Mount St. Helens Volcano. CEN Creation ex nihilo Technical Journal 10 #3 pp. 335-343  PDF available at www.icr.org/article/argon-mount-st-helens]

A group of scientists from Institute for Creation Research’s RATE Project [Radioisotopes and the Age of the Earth] prepared rocks and sent them to laboratories to be dated using several radioactive dating methods such as rubidium-strontium and uranium-238 – lead-206. In every case, the numbers were not at all consistent, sometimes exhibiting a wide spread. Dr. Austin had observed the same thing. With one lava flow which cascaded down into Grand Canyon, he calculated ages ranging from 100,000 years up to 2.6 billion years. [p. 126] That is quite a spread, but of course none of these values suggests an age of thousands of years.

The RATE Project also studied the decay of crystals in granite rock from a deep mine in New Mexico. The relevant observation was unexpectedly high levels of helium in zircon crystals in which uranium-238 had decayed to lead-206. In the decay process, eight atoms of helium are emitted for every atom of uranium changed to lead. But helium is very slippery and escapes quickly from any container. The diffusion rate was measured which indicated that most of the helium should have escaped long ago from the crystals. But it had not! The RATE scientists concluded that 1.5 billion years of uranium decay had occurred within the last 6000 years since the helium had not had time to diffuse at the observed rate.  While interesting, such conclusions suggest that temperatures hotter than the sun would have been generated in such a fast radioactive decay process. Obviously, that has not happened. Theoretical physicists are trying to figure out how such a varying rate of radioactive decay could actually have occurred.

The radiometric dating with which most people are familiar is Carbon 14 or C14.  In the air a neutron hits an atom of nitrogen 14 and turns it into carbon 14. This carbon combines with oxygen to become carbon dioxide. Plants photosynthesize and incorporate the carbon dioxide into plant material which animals later eat. Thus most organisms contain some traces of C14 . When the organism dies, it is no longer taking in food and the amount of radioactive carbon begins to decline. It decays back to Nitrogen 14. Scientists then calculate how long the process of decay of C14 has continued in any given artifact. However, there are a lot of uncertainties about how much radioactive carbon was present initially. Apparently, the amount of radioactive carbon is still increasing in the atmosphere relative to the rate of decay (secular equilibrium not yet achieved). Scientists try to calibrate radioactive carbon by counting tree rings in Bristlecone pine and then measuring the amount of carbon at that age. However, there are a lot of uncertainties in this process too. The problem is trying to overlap pieces of wood to get a continuous record going back.

Also, some scientists suggest that the pre-flood levels of C14 might have been very much lower as a result of a stronger magnetic field that would have deflected many cosmic rays so that they did not hit nitrogen14.  Apparently, there are other conditions as well which could have kept radioactive carbon levels low in the atmosphere before or immediately after the flood. All these conditions could result in radiocarbon measurements suggesting ages which are too old (the less carbon 14, the older the calculated age of the material).

It is obvious that we would like to know a whole lot more than we do about radiometric dating! However, our default position is that the earth is young. There is definitely no reason to reject what God has told us on the basis of some uncertain calculations based on assumptions which are uncertain in the extreme.

Related Resources

Related Terms

  • Cambrian Explosion
  • Sedimentary Rock
  • Flowering Plant Explosion
  • Body Plans