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The Latest Big Controversy on the Age of the Grand Canyon
Take a look at this group of people
Participants at the "Workshop on the Origin of the Colorado River", USGS, Flagstaff, May, 2010This represents the entire cohort of experts on planet Earth, who know something about the science of the origin of the Grand Canyon. There's about 60 of them, meaning there are not a whole lot of people in the world who regularly concern themselves with Grand Canyon's age.
So it was a big deal when the national media reported on the publication of a paper in the journal
by researchers Rebecca Flowers and Kenneth Farley on November 29. The article reported on evidence they obtained documenting an ancient Grand Canyon of about 70 Ma (million years). The date is more than ten times the age that most of the people in the photograph ascribe to the canyon, thus explaining why the press went hog-wild over a subject that normally hides in the shaded recesses of small tributary canyon. Who would have known that this story would fire up the creative juices of a nation still recovering from the long, drawn out presidential election.
Front page stories appeared in the New York Times, Washington Post, the LA Times, Huffington Post, the Seattle Times, and the Latino Post. The story went viral instantly in just about every small town newspaper in America and who knows how far and wide globally. (My hometown newspaper, the Arizona Daily Sun, ran a mistaken headline, "Jurassic Canyon", obviously trying to play off the Jurassic Park name, but missing the time period (Cretaceous) by about 80 million years). Broadcast media even chimed in, with NPR's "All Things Considered" running a 7:15 segment on the radio and PBS doing similar justice on the PBS Nightly Newshour. You can listen and watch these here and here.
Zoroaster Temple along the Colorado River in Grand CanyonTo put it mildly, most scientists who work in this field are not used to the attention. So why all the hoopla? Perhaps it's because research journals like
are not immune to the publicity-seeking payoffs that any media outlet strives for in our information blitzkrieg culture. That's not to say that there is no merit in the research (or the arguments against it). It just seems a bit strange that the only time the collective national ear is cocked in this direction is when two respected camps of researchers want to duke it out in a 'who's right/who's wrong' sockdolager.
As someone who is knowledgeable about Grand Canyon geology (yes, I am in the picture above but be forewarned that I rarely take sides in such matters, preferring to think that anyone who has come up with an original idea about the canyon's origin is likely to be at least partially right), my own in-box was slammed over the weekend. This is because my book was released in a new 2nd edition in late September of this year. Talk about a publicity windfall! Yes, the controversial idea is contained in the new edition and some folks here in Arizona have already heard of this controversy during the book tour I have been conducting since the book's release.
Cover of the 2nd editionWhat controversy you might ask? First off, it's not an entirely new idea. Flowers and Farley have been working with another Cal Tech researcher, Brian Wernicke, since at least 2008, when Flowers finished her PhD under Wernicke at Cal Tech. Wernicke adopted the idea from another "old canyon" geologist, Don Elston, who endured violent opposition to his ideas on the antiquity of the canyon during the late 20th century. There have always been researchers who find evidence for an "old canyon" and the idea has been around since the days of John Wesley Powell. Only since the 1930's has the idea of a "young canyon" emerged as the modern paradigm.
The new theory involves two very complex and complicated laboratory techniques that can reveal when the canyons rocks were brought close to the surface. Using tiny apatite crystals collected from the basement rocks in the canyon (Vishnu Schist or Zoroaster Granite), the information gave two different stories, one for the history of the western Grand Canyon and the other for the eastern canyon, where most tourists see the gorge. The results said that western Grand Canyon (downstream from Lava Falls) was cut to within a few hundred meters (about 1,000 feet) of its
present depth by 70 Ma
! And the eastern area had a
canyon of similar proportions
to the modern canyon by 55 Ma (but cut in Mesozoic rocks now completely eroded away). Incredibly, the older canyon was cut by a river that flowed exactly opposite to the modern Colorado River and the researchers call this river the California River. (Get it? The modern Colorado River goes from Colorado to California, while the ancient California River went from California to Colorado).
A view of western Grand Canyon, which may have been cut as early as 70 million years agoSuffice it to say that those who argue for a young canyon (one no older than 6 million years), find that the new results are tantamount to heresy. Researcher Karl Karlstrom of the University of New Mexico had a four-page rebuttal ready by press time and was quoted as calling the results "ludicrous". And while there may be some legitimate concerns he raises about the use of the technique, I wonder if this kind of response is, in the long run, all that good for the science or the public being exposed to it. This is Grand Canyon's moment in the sun, a time to cherish and nurture the opportunity to be heard on the national stage. Perhaps we geologists shouldn't take sides so quickly. Maybe we shouldn't view this as an attack on a cherished idea but merely another possibility that deserves to be heard and considered. The Grand Canyon has always had its adherents for an "old canyon". They are a minority for sure but the fact that this idea will not die is evidence enough that something must be there. That is my opinion on the "controversy".
When the Cal Tech group began their study they assumed that the apatite samples would reveal that Grand Canyon's rocks were buried in
of overlying rock - unequal because the canyon today has 5,000 feet of relief and the upper samples should have been buried under less material than the samples collected from the bottom. Most geologists would suspect a very subdued surface about 70 Ma. The illustration below (from my current lecture) shows red dots where the apatite samples were collected within the depths of the eastern Grand Canyon. The unequal length of the blue arrows depicts the amount of overlying material they expected to find.
After running the laboratory technique the samples gave the researchers a surprise. The results showed that no matter from what depth they collected the samples, they all appeared to have been
buried under equal amounts
of material. Connecting the tops of the blue arrows revealed the proposed topography in eastern Grand Canyon about 70 Ma.
And below is their interpretation of the data - a gorge of similar proportions cut into the Mesozoic rocks that are stripped back to the Echo and Vermilion Cliffs.
In my reading of the paper from
(not light reading I might add) I observed that the laboratory technique is not as evolved as one might hope for. Some assumptions are made that could result in different outcomes. Still, the technique has potential and even Karlstrom admits such a possibility. But he also wonders how a canyon could have been carved so early in time and then just sit there relatively unmodified for tens of millions of years. (Don Elston suspected that after being carved, the early canyon was partially filled with sediment and then exhumed in the last 6 million years).
It's true that the Park will not soon change the valid and useful number regarding the age of the Grand Canyon. What we see today from the canyon's edge is a gorge that has been greatly deepened and shaped in only the last few million years. The evolutionary history of the Colorado River shows that its exact course through the canyon to the Gulf of California was also accomplished in only the last 6 million years. But I want to make clear that most geologists too often
conflate the age of the river with an absolute age for the canyon
. For while the Colorado River is definitely no more than 6 million years old, the age of its ancestors and some early incarnation of the canyon need not be so strictly confined.
If we are to make sense of "When did the Grand Canyon form?", we should first ask ourselves, "What defines the Grand Canyon?". Karl Karlstrom and others like him say that the Grand Canyon must be a feature formed entirely by the modern Colorado River. I'm not so sure. Some aspects of the canyon, with respect to its depth or extent, could pre-date the modern river, having been formed by prior ancestors. Perhaps the question of "When did the Grand Canyon form?" can only be answered by another question: "What constitutes the beginning of the Grand Canyon?"
We are lucky that the world is paying us a visit at this time. Let's keep the debate civil, respectful, and without harsh words to our fellow geologists. We all seek the truth and each incremental step brings us closer to it. This is part of the process of getting to know a world-class landform that continues to inspire and enchant us all.
Title page to "Carving Grand Canyon" Photograph by George H.H. Huey