The Age of the Earth: How Interlinking Evidence from Tree Rings, Carbon-14, and Varves demonstrates an old earth
Posted by J.W. Wartick ⋅ February 4, 2019 ⋅ 3 Comments
Image from Wikipedia. Credit: By Copyright © National Land Image Information (Color Aerial Photographs), Ministry of Land, Infrastructure, Transport and Tourism, Attribution, https://commons.wikimedia.org/w/index.php?curid=28702247
What kind of evidence do we have to support the notion that the Earth is truly ancient? It's a question I often get asked, as someone who came from a young earth background. Young Earth Creationists often posit that the evidence for an "old earth," if viewed from a different angle, could just as easily (or perhaps better) point to a young earth. However, there are some aspects of evidence for an old earth that seem to defy this argument, particularly because they interlink in such a way that independently points towards an old earth. Here, I take a look at an article by Gregg Davidson and Ken Wolgemuth in which they make this very argument. Below is the title and abstract.
Testing and Verifying Old Age Evidence: Lake Suigetsu Varves, Tree Rings, and Carbon-14
Gregg Davidson and Ken Wolgemuth
Carbon-14 measurements from layered sediments collected in 2006 from Lake Suigetsu, Japan, together with tree-ring data, offer an unprecedented opportunity to demonstrate how competing old- and young-earth hypotheses can be quantifiably tested. Conventional observation of radioactive decay rates, atmospheric carbon-14 production, tree-ring growth, cross-dating, and varve formation yields a narrow range of expected values for the carbon-14 content of samples over the last 50,000 years. Young-earth challenges to each observation should result in specific and predictable departures from conventional expectations. This article documents a sequence of tests to demonstrate beyond reasonable doubt that carbon-14 decay rates have remained unchanged, estimates of past atmospheric production rates are accurate, cross-dating of tree rings is reliable, the sampled trees have grown one ring per year going back more than 14,000 years, and finely layered sediments from Lake Suigetsu were deposited annually going back more than 50,000 years.
Gregg Davidson and Ken Wolgemuth, in this paper, analyze three independent lines of evidence that interlink to confirm each other. Specifically, by looking at tree rings, varve formation, and carbon-14 dating, they yield a range of possible dates that matches across these independent variables. This gives a strong confirmation of the age of the earth, along with demonstrating that the decay rate of carbon-14 does not seem to have changed and remain accurate for more than 50,000 years.
The importance of this paper, and arguments like it, is that these are independent lines of evidence that all interlink to show the same conclusion. This needs to be emphasized, because young earth creationists will often call into question these pieces of evidence individually, shooting them down with objections that they then conclude shows they are individually faulty. Rarely, if ever, do young earth creationists acknowledge or deal with the fact that these evidences, while being independent, yield results that all add up to the same ages. Again, the importance of this cannot be understated, because it would mean that, for whatever reason, the young earth creationist must then assert that their independent objections to each individual dating method also can somehow explain why those dating methods to which they are objecting yield the same results.
Trees record the years they've been growing through rings that show how quickly their cells grew during different seasons. A record of years can be traced by comparing tree rings to show wet/dry seasons that form something similar to a bar code type pattern allowing for identifications across years. The oldest living trees have 5000 years recorded, and fossilized trees can be compared to living trees to extend that record back further, with the oldest reliable comparison yielding 14,000 years. Young earth objections to tree rings typically center around the notion that multiple rings form in single years.
Carbon-14 Dating
Wolgemuth and Davidson write that, in regards to Carbon-14 dating:
The primary requirements for determining age are (1) a constant radioactive decay rate, (2) knowledge of the original carbon-14 content, and (3) quantification of any old carbon that may have been incorporated into the specimen.
Standard young earth objections are leveled at each of these three requirements. However, it is rarely (if ever–though I'm sure someone does, somewhere) disputed that certain dates are yielded when Carbon-14 testing is done. Thus, it is the young earth objections to the three requirements where they rest their case. These objections are often that we cannot know whether the radioactive decay rate changed in the past; (less typically) that the original carbon-14 content is in question; and that the samples are somehow contaminated. Now, Wolgemuth and Davidson do clearly state that scientists must account for some known factors that can vary how quickly Carbon-14 is formed. But these can be accounted for and allow scientists to get fairly accurate data on dating samples.
Image source: http://www.suigetsu.org/varves.html Used under fair use. Accessed January 2019
Probably the least familiar of these dating methods to anyone with a passing interest in the age of the earth is varves. These are sets of alternating layers formed by sediment on the floor of bodies of water due to a number of factors. With Lake Suigetsu in mind, the method of dating involved is a measurement of algae blooms via examination of the varves. At this lake, cores have yielded dependable rates that allow dates traced back to around 150,000 years.
Independent Methods, Same Results
Where this gets interesting, and where young earth creationists ought to take note, is that while it is somewhat easy to discount individual pieces of evidence based on independent objections, it is much more difficult to do so when these allegedly faulty dating systems yield the same dates.
Carbon-14 dating methods allow scientists to make predictions for how much Carbon-14 ought to be present in a sample before testing the sample. Thus, scientists can use these predictions to chart what the expected Carbon-14 content of tree rings or varves will be. The article has just such a chart, yielding a very narrow range of expectations regarding Carbon-14 content with the age of the sample. They can then take tree rings, going with the conventional assumption that the rings indicate years, and sample them for Carbon-14 to see if they match the expectations of carbon dating. What is remarkable (visually, especially, again, see the article) is that these expected ranges correspond exactly to the samples taken of tree rings. This means that a tree ring yielding an age of 14,000 years due to the number of rings also yields an age of 14,000 years when sampled for Carbon-14. But these dating methods are completely independent. The Carbon-14 date doesn't rely at all on the number of rings in a tree, nor is reverse true.
Wolgemuth and Davidson then show the expectations from a young earth model with explanations of tree rings. For example, the expectation of multiple rings per year is tested and falls well outside the predictions of the Carbon-14 dating. This is important, because it means that the conventional assumptions about testing dates align together independent dating systems while young earth predictions yield wildly dissimilar results. These results are presented in the paper.
Scientists go further, though, and can line these evidences up with varves of Lake Suigetsu. Here, there is some technical data about how scientists can determine when significant events happened in the lake, such as extreme algae blooms or additional brackish water, but the core of the point is that when these factors are accounted for, a predictive range for Carbon-14 can again be made and set alongside the age estimate based upon the varve samples. Once again, when aligned, there is remarkable correspondence between Carbon-14 expectations and the actual measurements set alongside the varve-counting method of dating. Additionally, note Wolgemuth and Davidson, there is a steady decline backwards in the amount of Carbon-14 present, showing not a wildly erratic decay rate but rather a steady and predictable rate as one goes deeper into the sediment of Lake Suigetsu. These predictions falsify a young earth account, in part, because the young earth model "expects… massive sediment deposits during the flood year…" in addition to other expectations of many flood models for a young earth.
Next, Wolgemuth and Davidson turn to combining all of these lines of evidence together, demonstrating that the period of overlap where we can measure tree rings, varves, and Carbon-14 yields a graph just as predicted by conventional expectations, and that varves and Carbon-14 can be plotted much farther (due to their availability and the lack of reliable tree ring data older than 14,000 years), showing a constant alignment of these independent forms of evidence.
The authors state the decisiveness of this data and its implications for models of the age of the earth quite well:
we have two options. Option 1 is that God gave us amazing tools to test and verify that carbon-14 decay rates have not changed and sediments in Lake Suigetsu have been accumulating for more than 50,000 years. Option 2 is that God precisely manipulated multiple independent phenomena—tree ring growth, atmospheric carbon-14 production, and sediment couplet formation—to mimic conventional expectations.
More Methods of Dating
Wolgemuth and Davidson don't leave the evidence there, however, because more methods of dating can converge on Lake Suigetsu, allowing for additional independent dating. Argon-Argon dating from volcanic ash in the Lake yields a radiometric test that corresponds to Carbon-14 dating and tree ring data.
They note that most young earth creationists don't object when Carbon-14 dating is used on things that corroborate biblical materials, such as the Dead Sea Scrolls. Yet when one puts the data point for the Dead Sea Scrolls alongside the tree ring carbon data, we find that there is, again, alignment between the Carbon-14 dating for the tree rings, the actual counting of the tree rings, and the age of the Dead Sea Scrolls. This would mean that some form of manipulation of dating systems would have to yield the correct date for the Dead Sea Scrolls but incorrect dates by counting tree rings and Carbon-14 despite the fact that these align perfectly with the data for the Dead Sea Scrolls. And with this latter data, again, Argon-Argon dating with radiometric dating can be incorporated to show yet another independent method of dating.
Young earth creationists have not dealt with the fact that it is not just independent methods of dating that yield similar dates but rather that these independent methods correspond with each other and back each other up. On a young earth reading of the evidence, there is no explanation for why the allegedly mistaken methods of counting tree rings, varves, measuring Carbon-14 dating, and Argon-Argon dating from volcanic ash should all correspond with the same dates. After all, each of these is taken to be independently mistaken for different reasons and at different rates. But if that's true, then the observed data should be completely different from what it actually is. Additionally, the alleged accuracy for dating things in biblical archaeology is generally conceded by young earth creationists, and this dating for biblical artifacts also corresponds to other dating methods. Thus, the accurate date of the Dead Sea Scrolls corresponds with the allegedly inaccurate methods of tree ring counting, varve counting, and radiometric dating. What possible reason could there be for this to be the case? Going back to the words of Wolgemuth and Davidson, the most reasonable explanation is that God has given us the tools to study creation, and that these tools give us an accurate record of earth's history.
What options are there in the origins debate? – A Taxonomy of Christian Origins Positions– I clarify the breadth of options available for Christians who want to interact on various levels with models of origins. I think this post is extremely important because it gives readers a chance to see the various positions explained briefly.
What is the relationship between Christianity and science?- An Overview of 4 Views– How should the Christian faith interact with science? Do they interact at all? I survey 4 major views on these and other questions.