Dating the Grand Canyon

Stratigraphy of the Grand CanyonAs easily accessible American landmarks, Mt St. Helens and the Grand Canyon feature disproportionately in young Earth creationist publications. For example Brian Thomas’ Monday article was called Age of Grand Canyon Remains a Mystery.

It is one thing to calculate the age of a layer of rock – this is a textbook application of radiometric dating – but quite another to date a canyon, say, that has cut through said rock at an unknown point later on. Less direct methods of dating must be used, and there is therefore a greater potential for disagreement (at least between scientist’s interpretations of the results). The more generally accepted date for the age of this particular canyon is 5-6 million years, but a recent paper in Science offers evidence in favour of the alternative view, that it was carved almost completely by around 70 million years before the present. Both dates are much more than 6000 years, but that doesn’t faze Mr Thomas:

Science starts with observation. The Grand Canyon’s flat sedimentary rock layers actually extend across broad portions of North America. Evolutionists say that these layers formed during hundreds of millions of years. But at least three observations stand against the evolutionary age assignment. First, such long-ages fail to explain the tremendous time-gaps required by uniformitarian thinking, wherein the vast majority of the evolutionary geologic column is not represented. But a miracle would be required to hide the supposed tens of millions of years of erosion that left no trace in the sharp, flat contacts between layers.

To support his last two sentences Brian cites two Acts & Facts articles. The objections raised in each are a mix of invalid and plain wrong: Unconformities are no mysteries, and no miracle is required.

Second, radiometric dates for igneous rocks that formed when ancient lava squeezed in between Grand Canyon layers contradict one another and confound the sedimentary layers’ age assignments. They illustrate why ages obtained by radioisotope decay are not trustworthy.

The reference here is to a 1992 Acts & Facts article by Steven Austin, called Excessively Old “Ages” For Grand Canyon Lava Flows. A talk.origins FAQ by Chis Stassen summarizes what he got wrong – all that this illustrates is why Austin himself isn’t “trustworthy.”

Third, across 300 million supposed years, the strata never tilted! If they had, then the iconic Grand Canyon layers would be slanted wedges, not the pancake-flat wafers that they are. Is it realistic to believe that earthquakes, continental shifts, catastrophic impacts, or any other cause of strata tilting never occurred over such a time span?

This is the most interesting claim made by Thomas, and one that I can’t completely answer. One thing I can tell you is that, as the canyon is about 450 km long, a slant of a mere degree along this distance would require one end to be 7.8 km above the other, or nearly nine-tenths of the height of Everest – which doesn’t seem feasible. Then there’s the fact that such tilting (in a different direction) has occurred in the older rocks. And as Thomas doesn’t actually cite his claim that “the strata never tilted” I’m not even sure if it’s true. My inability to explain the claim here relates less to the inability of geologists to do so, than it does my own lack of geological knowledge.

Now at last we can get to the canyon itself:

Dating the layers’ time of deposition using scientific clues is clearly riddled with uncertainty. Are secular attempts to date the gorge—the time when water carved through the ancient layers—any more certain? The traditional view was that the Grand Canyon formed when the countryside started slowly uplifting around 70 million years ago. But radiometric dating of recent lava flows that span both sides of the Canyon demonstrated to uniformitarians that it was carved only five to six million years ago. One certainty about secular geologists is that they are continually uncertain about the Grand Canyon’s age.

I can’t vouch for the history that Thomas provides here – I don’t think the lava flows have much to do with it, more the erosional history extrapolated from what is presently observed.

The new results published in Science hearken back to the long-discredited 70 million years idea. This new date result compared the concentration of helium atoms trapped inside apatite minerals from eastern and western ends of the Canyon. How could so many experts for so many decades all have been an order of magnitude wrong about the age of the Grand Canyon?

The mechanism used in the paper involves the idea that helium will diffuse from apetites when the rocks are above a certain threshold temperature, and therefore buried deep within the bowels of the Earth. If the apetites are too cold for diffusion radioactive decay will cause an accumulation of helium. The date was derived from the observation that the apetites appeared to have cooled down – and therefore come relatively close to the eroding surface – around 70 million years ago. That’s a curious find, it has to be said.

Rebecca Flowers, lead author of the Science study, tried to waive off the age discrepancy. She suggested that the old “conventional models” that indicated 5-6 million years did not take into account the possibility that the canyon may have reversed its flow of direction at some time or times in the distant past, according to Science Now.

The quote from the Science Now article reads:

But those 5-million-to 6-million-year-old sediments don’t constrain the age of the canyon, only the direction of the river’s flow within it, Flowers says—and, for example, changes in the slope of the terrain over geological time could have altered the flow of the ancient river. Or the eastern and western portions of the canyon may have formed separately, joining only recently.

The latter explanation, not mentioned by Thomas, sounds more interesting to me. But he argues against the former instead:

For example, Flowers said, “changes in the slope of the terrain over geological time could have altered the flow of the ancient river.” But there is no evidence that the Canyon ever flowed backwards. And according to evolutionary age assumptions discussed above, there were no changes to the terrain’s slope for 300 million years. On that basis, why would anyone expect northern Arizona to tilt during the last 70 million, when Flowers suggests the canyon was carved?

But would that explanation actually require a major tilting of the crust, or are we just talking about the eroding surface at the bottom of the canyon? The Science Now article is ambiguous, and I can’t read the full paper. And do my eyes deceive me, or has Mr Thomas gone from saying “[i]s it realistic to believe that [...] strata tilting never occurred over such a time span?” to “why would anyone expect northern Arizona to tilt during the last 70 million [years].” Perhaps the canyon just tilted back – all we know is that the depositional surface ~270 million years ago has had little net tilting since, not that it hasn’t tilted. But again, I like the other explanation better, so far as I support this “old canyon” hypothesis.

Flowers may be convinced that her new results are reliable, but other experts are not. State University of New York geologist Richard Young told Science NOW that despite this new study, “there’s a lot of evidence for a young Grand Canyon.” And California Institute of Technology geologist Brian Wernicke said, “It’s hard to look at a landscape and discern its erosional history.”

Young’s line is here almost a quote mine – he means “young” as in “6 million years old,” but Thomas may be trying to imply that there is support for young Earth creationism. B.T. concludes:

The question arises again: will science ever resolve the Grand Canyon dating game? Considering that the debate about the Grand Canyon’s age is 150 years old and still going strong, the mere tools of science may never adequately unfold the pages of the past.

This article is very interesting in that here we have the standard dating of a geologic feature, 3 orders of magnitude too old for the YECs, being challenged by a new date that is an order of magnitude older. Thomas is unable to directly use this to support young Earth creationism – he can’t even offer his own explanation for Flowers’ observations – and the best he can do is talk about how the silly scientists cannot agree among themselves. Where in another context we might see confident assertions that the scientific evidence strongly supports the creationist explanation, we instead read that science may never know the true answer. Is Thomas admitting that he has nothing to support the ICR’s own theories, or has he remembered that he shouldn’t be contradicting the “historical science can never say things for sure” line of creationist argument?

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4 thoughts on “Dating the Grand Canyon

  1. Pleased to note – from your opening paras – that you agree with my comments posted under an earlier blog entry around 24 hours’ ago. :) This is no ‘radiometric dating controversy’.

    According to this article: http://www.nytimes.com/2012/11/30/science/earth/study-sees-older-grand-canyon-stirring-controversy.html?_r=0
    this paper: http://www.sciencemag.org/content/early/2012/11/28/science.1229390
    refers to an “implied a dichotomy in the late eastern and early western canyon origins” (suggesting formation at different times I think).

    The Thomas article does not mention this – not directly at least. (He does mention another claim by the scientists and retorts “there is no evidence that the Canyon ever flowed backwards”.)

    I’m assuming you haven’t – like me – had a chance/opportunity to read the full Flowers-Farley paper in Science magazine.

    • No, I haven’t read it, unfortunately. As I mentioned above, the differing formation times idea is the one that interests me the most, but as you say he doesn’t talk about it.

  2. Thanks for thinking about our results and defending the scientific process aimed at deciphering Earth history. Keep up the good work. If you drop me an email, I’ll send you a copy of our paper.

    In reference to one of your comments above, there is a huge dataset that indicates western U.S. topography, drainage systems, landscapes, and elevations have changed dramatically over the last 80 Ma. The region that is now the Colorado Plateau and Rocky Mountains were are sea level at 80 Ma.

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