How old is the Grand Canyon?

No, not 4,000 years.

The general consensus among geologists who have studied the erosional history of the Grand Canyon and its setting is that the Colorado River carved out the whole thing over about the last 4 – 5 million years. A combination of tectonic uplift to the north – growing the Colorado Plateau – and continental rifting in the south – opening the Gulf of California – steepened the flow of the Colorado River and sped up its waters. As a result, it carved through the painted strata beneath its bed at a colossal rate, until it hit the crystalline bedrock of the Vishnu Schist, which today outcrops along the bottom of the canyon.

But a new study (Polyak et al., Science v. 319, p. 1377 (2008)) challenges that view, and proposes that part of the Canyon started forming up to 17 million years ago… some 10 million years earlier than previously thought. This is a big deal, and a controversial one. The study is based only on two data points, and has received a lot of criticism by other Grand Canyon geologists. The details of the controversy are technical, but the gist is that Polyak and coworkers may have misinterpreted their two data points, and are using their misinterpreted data to build an alternate but incorrect picture of Grand Canyon history – one that doesn’t fit with a lot of other evidence that people have collected over the last 100 years.

This isn’t a case of kooks versus scientists… this is a real scientific controversy, and one that shows really well how science is supposed to work. The consensus age of about 5 million years is based on a lot of information from a lot of sources. Literally thousands of research papers over the years, based on tens of thousands of hours of field and laboratory work by hundreds of scientists, building up to a picture that shows a 4 – 5 million year old Grand Canyon. The new study claims to overturn all that, at least for part of the Canyon, so to be accepted it’s got to stand up not only on its own merits but also in comparison with all that other work. The new data will either stand up to that test, or they won’t. And no one really cares how the various parties to the argument feel about their positions. That – among other things – is what separates science from religion.

A lot of people don’t appreciate how scathing scientific battles can be. Here’s an example:

The highly publicized conclusion of Polyak et al. (1) that the western end of the Grand Canyon is more than 10 million years older than previously thought ignores and contradicts long-established regional geologic knowledge. We ask that the authors provide a rigorous justification of both their assumptions and their interpretations, specifically in the context of the well-published geology of the region. Considering this, we propose alternative interpretations of their two anomalous western Grand Canyon data points.

That is the beginning of a published critique of the Polyak 17-million-year figure, written by Joel Pederson of Utah State University and coworkers (Pederson et al., Science v. 321, p. 1634 (2008)). A second rebuttal (Pearthree et al., Science v. 321, p. 1634 (2008)) also calls the Polyak data into question. Polyak and company came right back with their own counter-rebuttal. This is what a healthy scientific debate looks like.

I don’t know who is right in this debate, and that’s the point. There is no way to know who is right, until the facts are checked and rechecked, the argument gets hashed out publicly in laborious detail, and a clear winner emerges. The winner will not be voted on by anyone. The winner will be the one most scientists end up going with because their explanation fits everything better. No unquestionable authorities, no cabals.

What is sad about this controversy is that the YECs are going to be all over it. The young-earth cretins don’t care about facts, only air time. If they can use this legitimate scientific argument to further their nonsense agenda, they’ll latch right onto it like the parasites they are. I can see the headlines now: SCIENTISTS BAFFLED OVER GRAND CANYON AGE! And that’s probably just what the mainstream US press will say.

The irony is that the upstart young mavericks in this debate are arguing that the Grand Canyon is older than previously thought. No matter. I’m sure the YEC pseudo-literature will crow and screech about how this is proof that not all scientists agree about how old the Grand Canyon is, and therefore it must be 4,000 years old and was carved out in 40 days.

Joel Pederson sums this up nicely in his rebuttal to Polyak’s study, where he expresses justifiable dread over how he, too, imagines this will play on the nightly news.

The famous landscape of the Grand Canyon lies along the front lines of competing scientific and nonscientific views of Earth’s antiquity and evolution. Regional geological knowledge of the Grand Canyon is especially rich and detailed, but it is already prone to unnecessary controversy and is frustratingly difficult to synthesize and communicate to the public. The report by Polyak et al. adds to the confusion rather than building upon previous science, and it therefore makes relating Grand Canyon science to the public even more challenging.

Unfortunately, he’s probably right.


~ by Planetologist on October 9, 2008.

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