The question of how the geologic timescale fits with the “young-earth” view is a good one. Not all scientists, and not all Christians, agree on how the evidence seen in geology can be harmonized with a young-earth account. Some, even those who believe the Bible is true and God is the Creator, deny that young-earth views can be harmonized with observations of the geologic timescale.
It is easy to be overwhelmed with conflicting claims. An avalanche of competing evidence, for those without deep scientific knowledge, is not especially helpful. In the end, the most reliable conclusion a non-expert can draw about the geologic timescale is that of open-mindedness. Nothing discovered in geology, in any sense, casts doubt on the veracity of the Bible. Scientists who take Scripture to be infallible and inerrant sometimes disagree on exactly how to interpret those observations. Since the geologic timescale is not a subject explicitly stated in the Bible, there is ample room for Christians to come to different conclusions.
Rock layers in the earth’s crust are examined by geologists to gauge how long ago those materials were deposited. In some cases, these layers, called strata, may contain remnants from plant and animal life buried and preserved through fossilization. In some cases, specific fossils are unique to certain layers, and are referred to as “index fossils.” Paleontologists—scientists who study ancient plants and animals—frequently use assumptions about fossils to date rock layers.
Critics suggest this creates a circular loop. Assumptions about fossil age are used to date rock layers; assumptions about the age of rock layers are used to date fossils. Those critics also point out that strata are not always found in their expected order. They also note that some rock formations show discrepant fossils: organisms that are preserved in the “wrong layer” based on paleontology’s assumptions. In some cases, it’s possible to find fossils from supposedly different eras preserved in the same rock.
The conundrum this poses for the non-scientist was succinctly stated by J. E. O’Rourke in the mid-1970s:
“The intelligent layman has long suspected circular reasoning in the use of rocks to date fossils and fossils to date rocks. The geologist has never bothered to think of a good reply, feeling that explanations are not worth the trouble as long as the work brings results. This is supposed to be hard-headed pragmatism” (“Pragmatism Versus Materialism in Stratigraphy,” American Journal of Science, vol. 276, January 1976, p. 47).
While O’Rourke’s comment has some truth, it also omits a lot of information. The “hard-headed pragmatism” of geologists is, in a sense, a reason to take their interpretations seriously. Secular or devout, a geologist is generally interested in understanding rocks such that one can make predictions and properly analyze the earth’s crust. This is especially important in the energy sector—e.g., fossil fuels—and in mining. Those industries in particular have provided literally hundreds of thousands of observations about strata. There is little incentive, and very much at risk, for any geologist to favor an inaccurate assumption.
Christian geologists, for example, point out that natural phenomena can cause geologic strata to be mixed or inverted. The basic geologic timescale used today predates Darwin’s theories of evolution. In fact, this general system was finalized by devout believer John Phillips, who debated Charles Darwin on such issues. At the very least, this indicates the modern geologic timescale is not in any sense dependent on certain views of evolution.
Those same Bible-believing scientists also note that the development of an old-earth geologic timescale was driven more by the discovery of processes that give every appearance of requiring long times to complete. When radiometric and astronomic observations of the early twentieth century matched those observations, it seemed to confirm that the geologic timescale—at least by appearances—is much older than what is suggested by young-earth views.
Ultimately, the geologic column and the accepted geologic timescale are like most other aspects of human knowledge. They are fallible and subject to change but not to be dismissed entirely. More importantly, it is not necessary for a Christian to hold dogmatically to either a young-earth or old-earth view to be faithful to Scripture. Arguments of various types, with varying validity, can be made for either side.
All Christians should agree, however, on two crucial points. First, it is possible for God to have created a young earth that has the appearance of great age. Second, widespread scientific observation unmistakably gives the impression of an “old” earth. What exactly that means so far as Scripture is concerned is open to a certain level of personal liberty.