The Creation Explanation
|The Age of the Earth|
The above examples of problems and difficulties in the various systems of radiometric age analysis bring into question the validity of the fundamental assumptions upon which the systems are all built. Assuredly much radiometric dating information has been assembled which appears to show extensive agreement between measurements and methods. On the other hand, since in many cases the assumptions lead to contradictory or absurd results, how can it be established that the assumptions are valid in any case? Furthermore, the assumptions have to do with supposed events in the distant past for which there were no human observers, and the basic time scale for these alleged events has already been agreed upon on the basis of evolutionary philosophical principles. Therefore, is not the evidence adduced in support of imagined scenarios of geologic activity and radioactive decomposition actually circumstantial? And do not the complex corrections, rearrangements, and reinterpretations of data that are devised to explain or remove discordant results take on considerable ad hoc character?
In the light of the many physical evidences for a young earth and the problems with radiometric chronologies reviewed above, creationists feel justified in rejecting or at least questioning seriously the great-age chronologies which are built on evolutionary presuppositions.
On the other hand, there is still a great deal of work remaining for scientists involved in developing a valid creationist model for interpreting the data of the geological sciences. One important problem has been the correct understanding of isochrons, a type of graphical correlation of isotopic ratios in a set of rocks or mineral crystals. Isochrons are used quite commonly with the rubidium/strontium radioactive decay system.
An isochron is a graph in which two isotopic ratios are plotted against each other. The data plotted are taken from the analyses of a set of different rocks or mineral crystals in a particular geologic formation. In rubidium/strontium isochrons the two ratios plotted are 87Sr/86Sr versus 87Rb/86Sr. In theory if the various rock samples formed from the same original magma source, the isochron plot should be a straight line, provided the rocks or mineral crystals have been closed to either loss or addition of the several isotopes. From the slope of this line the time since crystallization can be calculated. Rubidium/strontium isochrons often are very poor or non-existent, but sometimes they are quite good straight lines, fitting well with the interpretation which assigns great ages to the rocks.43 Recently, however, Russell Arndts and William Overn discovered that such an "isochron" can be explained in terms of the mixing of two different source magmas which had different beginning contents of the pertinent isotopes.44 The mixing of magmas and crystallization of the rocks could have occurred quite recently. Therefore, a rubidium/strontium "isochron" may actually be simply a mixing curve which has nothing at all to do with great age. Furthermore, there is no way with certainty to distinguish an isochron from a mixing curve. In this connection it is significant that in some recent isotopic studies of extensive geological structures the rubidium/strontium data have been interpreted in terms of mixing of different source magmas. Faure and Powell discussed briefly in their 1972 book, Strontium Isotope Geology.45 Fourteen years later in his book Principles of Isotope Geology, Faure confirmed that mixing of two source magmas can result in "fictitious isochrons" which yield false age estimates.46 These contradictions and anomalies are found in the radiometric analyses of Grand Canyon igneous and volcanic rocks using three major methods, uranium/lead, potassium/argon, and rubidium/strontium.
Grand Canyon Radiometric "Ages" Raise Doubts about Radiometric Chronologies
Dr. Steven Austin, a geologist of the Institute for Creation Research, has conducted the most recent and ongoing studies of problems and anomalies in radiometric chronologies.47 Anomalies in the radiometric age estimates of volcanic rocks in the Grand Canyon seriously undermine the reliability of several major radiometric methods used by geologists to estimate the ages of rocks. Using analysis of published radiometric age studies, augmented by new measurements, Dr. Austin, shows that the youngest volcanic rocks located on the top of the sedimentary strata in the Grand Canyon yield "ages" which are a billion and more years "older" than the age values obtained for supposedly much older rocks buried deep under the sedimentary layers. Dr. Austin concludes that the volcanic rocks of the Grand Canyon have inherited isotope ratios which give them a false appearance of great age. He points out that the problems in the results of radiometric age determinations lie not in the technology used, which is excellent, but in the assumptions which must be made in order to use the results to estimate the ages of the rocks.
43. Wasserburg, G.J. and M.A. Lanphere, Geological Society of America Bulletin, vol. 76, 1965, pp. 735-758.
44. Arndts, Russell and William Overn, Bible-Science newsletter, Vol. 19, April 1981, pp. 5-6; ___________, Radiometric Dating: Isochrons and the Mixing Model (Bible-Science Association, Minneapolis, 1983).
45. Faure, G. and J.L. Powell, Strontium Isotope Geology (Springer-Verlag, New York, 1972), pp. 34-35.
46. Faure, Gunter, Principles of Isotope Geology, Second Edition (John Wiley, New York, 1986), pp. 141-151.
47. Gish, Duane T., Steven A. Austin, et al., Institute for Creation Research Grand Canyon Field Study Tour Guidebook (Institute for Creation Research, Santee, CA, 1990), pp. 83-109.