This is Part 2 of the Creation & Origins series. Part 1 — Why This Is So Hard laid out the hidden assumptions both sides bring to the evidence. This post takes on the biggest one: how old is the earth, and how do we know?
Why Time Is the Load-Bearing Wall
It’s worth noticing, before getting to any rock at all, just how much depends on the answer to “how old is the earth?” — for both sides.
On the mainstream side, deep time isn’t a peripheral detail. Charles Lyell’s proposal of a vastly ancient earth directly shaped Charles Darwin’s thinking — Darwin read Lyell and became convinced that immense stretches of time could turn small, observable changes into the common ancestry of every species alive. Take the millions of years away, and the mechanism most often proposed for macroevolution loses the one resource it can’t do without: time enough for tiny changes to add up to enormous ones.
On the creation side, the stakes are just as structural, for a different reason. The genealogies that run through Genesis aren’t decorative — they’re the connective tissue of the whole biblical narrative, picked up again in Ruth to establish David’s line, and again in the Gospels to trace Jesus back through Mary and Joseph all the way to Adam. If that lineage is meant to be read as real generations rather than symbolic gaps, it anchors creation to a timeline of thousands of years, not billions. Pull on that thread and you’re not just adjusting a date — you’re asking whether Christianity’s claim to be grounded in actual history holds up.
Neither side is dispassionate about this number. That’s exactly why it deserves a careful, unhurried look.
How Radiometric Dating Actually Works
The basic idea is genuinely elegant. Certain elements are radioactive — their atoms are unstable and decay over time into a different “daughter” element, at a rate that can be measured in the present. When volcanic rock crystallizes from molten lava, it locks in a snapshot: a certain ratio of the original “parent” element to whatever daughter element has accumulated since. Measure that ratio today, know the decay rate, and in principle you can calculate how long ago the rock solidified. Geologist Andrew Snelling, who holds a PhD in geology and has worked on this question for decades, puts the core logic plainly: because these decay rates are so slow when measured in the present, the math produces ages in the millions of years — that’s ultimately where the deep-time numbers come from.
Notice what that method quietly assumes, though: that the decay rate has been constant the whole time, that no daughter element was already present when the rock formed, and that the system has stayed closed — no parent or daughter material added or removed by outside processes since. Every one of those is a reasonable working assumption. None of them is something anyone watched happen.
When the Same Rock Gives Different Answers
Snelling’s sharpest claim isn’t philosophical — it’s a direct empirical challenge. He describes taking identical rock samples from multiple sites (the Grand Canyon among them) and submitting them to more than one radiometric dating method. On the same sample, different methods sometimes produced ages differing by hundreds of millions of years, and in some cases by close to a billion. His conclusion: if the system were reliably closed, independent methods applied to the same rock ought to agree. When they don’t, that’s evidence the “closed system” assumption is being violated — and if it’s being violated in ways we can catch, Snelling argues, we should be cautious about trusting the method where we can’t independently check it.
The Mainstream Reply — Taken Seriously
This is exactly the kind of claim that deserves the strongest available counter-argument, not a token one. Mainstream geologists don’t dispute that discordant dates exist — they’re documented in the peer-reviewed literature. Where they disagree is on what the discordances mean.
The sharpest discordances — the kind that produce wildly inflated ages on rock known to be recent, like historic lava flows — tend to cluster around one particular method (potassium-argon dating) and one particular known failure mode: “excess argon,” where argon gas already present in the magma gets trapped in the rock as it cools, inflating the apparent age before any decay-based clock even starts running. That’s a recognized, well-documented problem with that specific method under specific conditions — not a demonstration that radiometric dating as a whole is unreliable. Geologists have developed methods precisely to catch this: isochron dating, for instance, uses multiple samples from the same rock body to detect and mathematically correct for exactly this kind of contamination, rather than trusting a single measurement at face value.
On genuinely ancient rock, the mainstream case rests less on any single method and more on convergence: multiple independent decay systems (uranium-lead, rubidium-strontium, samarium-neodymium — each with completely different decay rates and different potential failure modes) tend to agree with each other on the same ancient rock formations far more often than a random, unreliable process would predict. And for more recent history, radiometric dating isn’t standing alone at all — it’s cross-checked against tree-ring counts, ice-core layers, and lake-bed varves, independent clocks that don’t rely on radioactive decay at all and that extend a consistent, countable record back tens of thousands of years.
Prediction vs. Accommodation
This is a good place to name a distinction that will come up again throughout this series. The flood/young-earth model doesn’t just tolerate discordant dates after the fact — it actively predicts them: if decay rates, deposition rates, or both were altered by a catastrophic global event, then methods assuming constant rates should produce inconsistent, conflicting results when applied across that boundary. The mainstream model, by contrast, accommodates each discordant result individually, after encountering it, with a specific known mechanism (excess argon, sample contamination, weathering, mineral resetting).
Both of those are legitimate explanatory strategies — accommodation isn’t automatically weaker than prediction, especially when the accommodating mechanism is independently verifiable and not just invented to save the theory. But it’s worth being honest about which posture each side is in in this exchange, because the two feel very different at the level of confidence, even when both are intellectually respectable.
A Second Assumption, Hiding in Plain Sight
Snelling makes a related but distinct case using the Grand Canyon’s rock layers themselves, independent of any radiometric measurement at all. The Coconino Sandstone — one layer in that famous stack — can be traced consistently across roughly 200,000 square miles, from Arizona into New Mexico, Colorado, and beyond. At certain boundaries between layers, there’s no visible erosion at all — no gap, no weathering — which Snelling reads as evidence that one layer was deposited essentially immediately after the one below it, with no long pause between. Two hundred thousand square miles of consistent sediment with no erosional gap between layers is, he argues, much harder to explain as slow, ordinary accumulation than as one continuous, rapid depositional event.
The honest mainstream counter here is that absence of visible erosion at a boundary doesn’t by itself rule out a long, quiet gap — some environments simply don’t erode much even given plenty of time, and geologists have their own toolkit (like matching regional rock sequences against known deposition rates elsewhere) for testing how much time a given boundary represents. That’s a real, ongoing area of active geological debate rather than a settled question either direction — which is precisely why it belongs in this series as a genuinely open thorn, not a decided case for either side.
🎥 A Different Angle: Video Explainer
This isn’t a rehash of what you just read. The video below approaches the dating question from a different angle than the essay above — a good gut-check before moving into the next post.
Where This Leaves Us
Radiometric dating is not the slam-dunk either side sometimes presents it as. It’s a genuinely clever method resting on assumptions that are reasonable but unprovable, producing results that are usually consistent but sometimes dramatically aren’t — and both sides have real, non-trivial things to say about why. What should be clear by now is that “the rocks just tell us how old they are” was never quite true for anyone. The rocks give measurements. Both paradigms do the work of turning those measurements into a story.
Next in the series, we leave dating methods behind and go to the fossil record itself — specifically, a pattern in the rock that may be the single hardest thing in this whole series for the conventional timeline to explain cleanly: footprints found in rock layers laid down, by every conventional measure, before the animals that made them are supposed to have existed.
🎧 A Different Angle: Audio Overview
Not a rehash — a short, conversational audio walkthrough of this post’s core argument, useful for revisiting the material on a commute or a walk.
Go Deeper: The Full Source Documentary
Andrew Snelling’s radiometric dating and Grand Canyon field segments referenced in this post appear roughly two-thirds of the way through the same film cited throughout this series.
Is Genesis History? (2017) — full film.
This is Part 2 of the Creation & Origins series. Next: Death in an Instant — trackways, graveyards, and the flood record.
📖 From the Same Author — The Divine Fractal
The Fractal Bible Series by R.M. Mayes
If the order and design running through this series speaks to you, it isn’t the only place Scripture shows its architecture. The Fractal Bible series traces a single pattern — Creation, Fracture, Restoration — repeating at every scale of the biblical text, from a single verse to the whole sweep of redemption history, grounded in thirty years of reading Scripture cover to cover. Same conviction as this series, applied to the text itself: the patterns aren’t accidents.
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