How old is the Grand Canyon?

Grand Canyon photo by Rebecca Flowers via Science

[Still fiddling with new blogging software. It’s easy. Just not as easy as Not Blogging At All.]

Here’s my story on the Grand Canyon that ran in Friday’s paper. We have a Young Canyon consensus and an Old Canyon conjecture. The Old Canyon camp is gaining a little bit of ground, thanks to the new paper by Rebecca Flowers in the journal Science. I have no idea who’s right here (my thermochronological skills are rusty), but in such situations it’s usually unwise to throw out the consensus just because some beguiling new data have come along. The critics of Flowers don’t doubt that she’s got good data, but they challenge her interpretation (see Richard Young and his receding cliff as an alternative to an ancient canyon). Geologist Joel Pederson offers something of a compromise interpretation: He believes she’s found a 70-million-year-old paleocanyon that is much older and bigger than anyone knew existed, but that precursor canyon still isn’t the Grand Canyon we see today, which is only 6 million years old.

The research on the Grand Canyon provides a reminder that science marches onward through a dark terrain – the buried past, in this case. Professional science is conducted at the edge of the knowable, in realms fraught with uncertainty, with results that are often ambiguous. The easy stuff has already been figured out.

The deniers of climate change famously exploit debate and uncertainty among scientists to create doubt about whether the planet is warming due to human activity. The job of science journalists is to provide robust coverage of scientific disputes without implying that there are no solid facts in this world of ours and everything’s just a lot of guesswork (and what scientists call arm-waving)

Here’s an excerpt of my conversation with Melissa Block Friday (you can also find an audio link by clicking on this) on All Things Considered:

BLOCK: And let’s give a sense of the tone of this debate here, because another key Grand Canyon geologist called Flowers’ conclusion ludicrous. He says it’s out in left field. Why is this such a hot topic?

ACHENBACH: Yeah, it’s interesting that Rebecca Flowers, Dr. Flowers, actually collected a lot of her samples with this other scientist, Karl Karlstrom, who is a critic of her conclusions because, you know, they have to raft down the river and chip away at the rock on the canyon walls and get these samples.

But this is a basic question of: What are we looking at here? When you stand on the rim of the Grand Canyon, what are you looking at? Now, obviously it’s a canyon carved by a river. You see the Colorado River at the bottom. So the causality seems pretty clear, except this new hypothesis says that much of the canyon goes back 70 million years and was carved by a different river, in fact two different rivers, neither of which was the Colorado River.

And so this is – this is a new idea based on some new scientific techniques, and it has really roiled the waters of that community of geologists.

Joel Achenbach writes on science and politics for the Post's national desk and on the "Achenblog."

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Joel Achenbach · November 30, 2012