Millions of Years

I find that persons advocating a Bible-based, often literal, creation story misunderstand science to the extent that it undermines their argument. "Because evolutionists assume millions of years, they believe... [fill in the blank usually with evolution]" is a creationist mantra commonly provided in rebuttal to science-based arguments. Typically, this assertion is followed by a list of evidence that either demonstrate things happen rapidly (fossils of animals giving birth, burial of coal, fossilized pliers, hats, flour sacks, and others), or that things shouldn't be as they are if the Earth were as old as evolutionists claim (oceans should be saltier or filled with sediment, the Cliffs of Dover shouldn't be cliffs or the continents should have eroded flat, and others). In actuality, these pieces of evidence are misinterpreted by creationists based on the mistaken assumption that "evolutionists assume millions of years." They (we) don't.

In this context, evolutionists are sedimentologists, stratigraphers, and paleontologists; I'll refer to practicioners of these disciplines as geologists. I have indicated in previous posts (Principles of Geology and Fossils and Circular Reasoning) that geology is founded on a set of simple guidelines: the principles of superposition, original horizontality, and lateral continuity. Superposition and original horizontality are based on the assumption that gravity works (in the Newtonian sense, Einstein's refinements don't significantly affect the actions of these geologic processes). Lateral continuity is a logical extension of superposition and original horizontality. These concepts are in the geologist's toolbox along with cross-cutting relationships, unconformities, uniformitarianism, and faunal succession¹.

One refinement I have yet to mention is the concept of facies: aspects and characteristics of a rock layer that change laterally (horizontally) are often repeated vertically. This concept is known as Walther's Law and is an observation as close to a "law" as geology is going to get. See for example wikipedia and Depositional Systems and Environments.

At no point in this toolbox, has a geologist assumed "millions of years." Rather, by observing the rocks and applying these basic principles, geologists have made two monumentally important observations which have been repeatedly demonstrated and tested. Each rock layer tells a different story about the processes that created it. Rock layers can be placed in order. In a continuous vertical sequence of rocks the order is obvious. The application of superposition, lateral continuity, and faunal succession is especially useful for ordering rock sequences separated geographically.

Even before the geologic record² was established in its current form, the concept of uniformitarianism suggested the Earth had to be more than a few thousand years old. If a succession of rocks provides evidence of being formed as the result of differing processes, there must be sufficient time not only to form each layer in the deposit, but time must also pass to allow for observed changes in the depositional settings. Just as sediments deposited by tides reflect daily cycles, the time required to form a succession of sandstone, shale, and coal must include not only the time to make the layers, but also the time needed to transition from oceanic to swamp settings. It can't be a single setting; trees and ferns don't grow at the bottom of the ocean. It requires even more time when like sequences comprising multiple transitions from ocean to swamp are stacked one upon another (for example: cyclothems in the Carboniferous). Another of my favorite cyclic rock sequences is the Castile Formation.

There was an early, but failed, effort to determine the age of the Earth based on sedimentology and stratigraphy. Uniformitarianism suggested the rate of sedimentation occurring in a depositional setting can be measured based on the rate of observable processess. If the rate at which a rock type is formed and its thickness is known, elapsed time can be estimated. Then, just add up all the elapsed times for all the layers and the Earth is that old. An obvious problem to this proposal is the presence of unconformities (gaps in the record representing a period of time of no deposition or erosion). Other problems include the same rock type can form at different rates and arriving at an exact count of the number of layers. This exercise, however inaccurate, demonstrated beyond the shadow of a doubt that the Earth was certainly older than 6,000 years and on the order of millions of years.

The bottom line is that rather than assuming millions of years as is asserted by creationists, the multi-million-year age of the Earth is the logical implication of applying a uniform set of simple guidelines to place Earth's rock record in order to facilitate their systematic study. It was not until the invention of radiometric age dating techniques that it was discovered just how many millions of years (4,500 million plus or minus a few million).

¹In this context, faunal succession neither assumes nor demonstrates evolution. The term simply means what William "Strata" Smith intended: the collection (assemblage) of fossils that occur within a rock unit are characteristic of that unit. And, this doesn't refer only to vertebrate macrofossils, it includes microfossils (plant and animal), invertebrates, and trace fossils.

²I am speaking here of the rock record, that is, the observable order of rocks resulting from the application of basic geologic principles. Once the framework of the order of rocks was determined, the order (succession) of fossils in that rock record, the "fossil" record, began to take shape. As more fossil data accumulated, the utility of those fossils to resolve detailed rock order (stratigraphic) questions became obvious enabling the correlation and ordering of rock units that weren't laterally contiguous or directly stacked. When viewed as a whole, the rock and fossil records comprise the relative time scale. The Geologic Time Scale is that relative time scale with age dates derived from radiometric analyses. The succession of fossils in the rock record provide powerful support for the Theory of Evolution and absolute (radiometric) age dating demonstrates the process took much longer than 6,000 years.