Perhaps this article can "evolve" into a FAQ someday (any professional geologists out there willing to help out?). The topics that I plan to cover:
1. How the column was originally assembled
2. Later independent verification methods
3. A few common creationist objections
It is important to note that the column was not assembled originally as a series of events or formations spaced by determinate amounts of time (i.e. an absolute sequence). Rather, it was assembled as a relative sequence (i.e., X before Y before Z), without any solid idea of the timing of these events, or what if anything was missing from between them. The key role in this development was played by the Principle of Superposition (younger sediments overlie older ones).
The Phanerozoic periods were first identified in Europe. In fact, one could take a stroll and encounter formations representing all of the periods, overlain in order (this is more convenient than digging thousands of feet to get to them, but one could do that as well). The following cross-section of Europe represents a straight-line route which starts in Northwestern Wales, and ends at London (curvature of the earth ignored; vertical scale greatly exaggerated; diagram slightly simplified):
NW Wales London ------------------------------------------------------------------------------- cccccOOOOOOOOOsssssssDDDDDDDiiTTTTTTTTTTTTTTjjjjjjjjjjjKKKKKKKKpppppppppppppppp cccccccOOOOOOOOOOOOssssDDDDDDDDDiiTTTTTTTTTTTTTTjjjjjjjjjjKKKKKKKKppppppppppppp BBBcccccccccccccOOOOOOOsssDDDDDDDDDDiiTTTTTTTTTTTTTjjjjjjjjjjKKKKKKKKKKpppppKKK BBBBBBcccccccccccccOOOOOOssssDDDDDDDDDDDiiTTTTTTTTTTTTjjjjjjjjjKKKKKKKKKKKKKKKK BBBBBBBBBBBBcccccccccccOOOOOssssssDDDDDDDDDDiiTTTTTTTTTTTjjjjjjjjjjKKKKKKKKKKKK BBBBBBBBBBBBBBBBBBBccccccOOOOOOOsssssssDDDDDDDDDiiTTTTTTTTTTjjjjjjjjjjjKKKKKjjj BBBBBBBBBBBBBBBBBBBBBBBBBccccOOOOOOOssssssDDDDDDDDDiiTTTTTTTTTjjjjjjjjjjjjjjjjj BBBBBBBBBBBBBBBBBBBBBBBBBBBBBccccOOOOOOsssssssDDDDDDDDiiTTTTTTTTTjjjjjjjjjjjjjT BBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBBccccOOOOOOssssssDDDDDDDDiiTTTTTTTTTTTTTTTTTTTT B = basement igneous D = Devonian K = Cretaceous c = Cambrian i = Carboniferous p = Paleogene O = Ordovician T = Triassic s = Silurian j = JurassicThis was derived from figures in: Evolution of the Earth, Dott & Batten, 1988 (4th edition), p. 54 Historical Geology, Carl O. Dunbar, 1949, p. 182 (I will send photocopies of the figures to anyone who asks me via Email.)
This is basically how the column was originally identified and assembled; all of the periods are found in order where geology was born. The use of index fossils and such helped to identify the same formations in the same order *elsewhere*, which further strengthens the original order.
For further information:
A Trip Through Time, Cooper, Miller, and Patterson; Columbus, Merrill Publishing Company, 1990 (second edition). Chapter 6 (pp. 154-186)
Great Geological Controversies, A. Hallam; New York, Oxford University Press, 1989 (second edition). Chapters 1-3 (pp. 1-86)
More important than the method used to originally assemble the column are methods invented since which can be used to test the ordering.
While "superposition" (without assumption of time intervals) is not very controversial, it is also not surprising that the column is in agreement with it -- for that is how it was put together. However, an ordering method which wasn't dreamed of when the column was originally assembled is the best sort of verification that one could hope to get.
A) Radiometric dating
Radiometric dating was conceived in the first half of this century. While it does have limitations and requires certain historical assumptions be valid, radiometric dating methods produce results in concordance with position in the geologic column about 95% of the time. Provided that there are reasonable explanations for the 5% anomalous cases, this is an independent test against the ordering derived by stratigraphy.
For example, K-Ar dating was tested against the North American Land Mammal ages of the Cenozoic, whose ordering was originally derived stratigraphically:
Stratigraphic K-Ar Date # Samples Position Name of Age (x10^6yr) Dated ======== ============ ========= ========== 1 Irvingtonian 1.36 1 2 Blancan 1.5 - 3.5 7 3 Hemphillian 4.1 -10.0 8 4 Claredonian 8.9 -11.7 16 5 Barstovian 12.3-15.6 9 6 Hemingfordian 17.1 1 7 Arikareean 21.3-25.6 4 8 Orellian --- 0 9 Chadronian 31.6-37.5 9 10 Duchesnean 37.5 3 11 Uintan 42.7-45.0 2 12 Bridgerian 45.4-49.0 2 13 Wasatchian 49.2 1 14 Puercan 64.8 1(Table from the Dalrymple paper, listed in references below, which is available from Wesley Elsberry for postage cost.)
Clearly, in this example, the ordering derived from radiometric dating and the ordering derived from stratigraphic position are in agreement.
The primary reasons why the ordering of the geologic column is accepted as originally assembled are: 1) consistently finding the same formations in the same order all over the world (though there are many places where some are missing, the relative position is quite dependable); and 2) independent confirmation of that ordering from radiometric dating. However, there are several other minor independent means by which we could order the column. I will explain one example:
B) Astronomical dating
Astronomers propose that tidal forces have been slowing the earth's rotation at a miniscule (and probably variable) rate. This means that the number of days in a year has slowly been decreasing over time.
I have somewhere (but I couldn't find it this weekend) a study on the number of daily growth layers per year in various fossilized creatures (corals and stromatolites, mostly). These values, used as an ordering method (higher number of days per year = older) provides the same ordering as both stratigraphy and radiometric dating.
An article covering only corals is available as Scientific American Offprint #871 (Runcorn, R. K., 1966, "Corals as paleontologic clocks").
Principles of Isotope Geology, Gunter Faure; New York, John Wiley and Sons, 1986 (second edition). A technical handbook/textbook.
USGS Open-File Report #86-110, G. Brent Dalrymple; United States Geological Survey, 1986. A response to creationist criticisms on radiometric dating.
Geologic Time, D. L. Eicher; New Jersey, Prentice-Hall, 1976. Details several dating methods (including "coral clocks").
Perhaps Jim will aid me in filling out this list. However, I'll pick a few examples from the literature that I have for now.
A) Circular reasoning. Creationists claim that the fossil record is ordered by the assumption that life evolved in a certain manner, and therefore the appearance of evolution in the fossil record is not surprising (e.g., Morris & Parker, What is Creation Science?, pp. 240-243).
The geologic column was first assembled and ordered by scientists who did not accept evolution. It therefore cannot be the product of the assumption of evolution in any manner.
The quotations which creationists present, in regard to possible circularity, involve the use of so-called "index fossils." These fossils were in use by geologists long before evolution was accepted. Rather than being any presumed "evolutionary age", they are merely fossils which are only found in a narrow range in the column. When found in a formation whose age is unknown, that formation is assumed to hold the same position in the column as other formations that have identical fossil content.
If the fossil record looked like the ICR wants you to believe, the use of index fossils never would have occurred. Geologists never would have found any fossils that are restricted to only a narrow range of strata. Even the creationists will admit that this isn't the case, on occasion:
"Many scientists, both creationist and evolutionist, would agree that there is a distinct order to the geologic strata, with characteristic fossils occupying the different layers. It is important to remember that the 'geological column' was worked out in the early 1800s, before Darwin published the *Origin of Species*, by men who almost universally believed in creation." [Sylvia Baker, Evolution: Bone of Contention, p. 15]Note that, to be fair to Parker, he goes on to claim that "ecological zonation" can explain the ordering. To be unfair to Parker, Wonderly goes on to explain why that's a ridiculous idea.
"Scientifically, the major challenge facing Flood geologists is the regularity of the fossil record. If the flood and its aftermath were responsible for the deposition of the fossil record, would not plants and animals be all jumbled together? Sometimes fossils are jumbled together .... Still, the majority of fossils are associated consistently with identifiable systems such as the Cambrian, Ordovician, etc." [G. Parker, The Fossil Record in Christian Perspective, p. 77 in Wonderly, Neglect of Geologic Data, p. 59]
C) Radiometric dating methods don't always work. Creationists will point to lists of anomalous results as if they invalidate the methods.
The problem for scientists is that they must explain why radiometric dating methods fail to produce concordant values about 5% of the time. Since the requirements for a valid date are usually stated up front, what is involved is usually the violation of one of the requirements.
It is quite common for scientists to be able to explain the exact reasons which yielded the invalid date. For example, "Big Daddy?" (Jack Chick) claims that a living mollusc dated by Carbon 14 to about three thousand years in age. The anomaly is explained by the fact that molluscs derive carbon from sources other than the atmosphere (e.g., weathered carbonate rocks) and therefore invalidate the initial conditions for "carbon dating."
The problem for creationists is that they must explain why radiometric dating methods produce concordant values 95% of the time. This sort of consistent performance cannot be explained as random luck. A process which yields concordant (but misleading) results must be demonstrated.
I suppose that if I gave a creationist five alarm clocks, each of which worked 95% of the time. When they all said it was time for him to get ready for work, I wonder if they would be ignored? There are plenty of cases where multiple radiometric dating methods agree on the age for a given object.
Neglect of Geologic Data: Sedimentary Strata Compared with Young-Earth Creationist Writings, Daniel E. Wonderly; Pennsylvania, IBRI, 1987. An old-earth creationist blasts young-earth creationists' comments on the geologic column. Available for $8.45 (postage and handling included) from IBRI / P.O. Box 423 / Hatfield, PA 19440. Should be required reading for any young-earth creationist.