Grand Canyon older than previously believed

 

Arizona, USA

To stand on the South Rim and gaze into the Grand Canyon is to behold an awesome immensity of time.

The serpentine Colorado River has relentlessly incised a 280-mile-long chasm that in some places stretches 18 miles wide and more than a mile deep. Visitors to Grand Canyon National Park will encounter an exhibit titled the Trail of Time, and learn that scientists believe the canyon is about 6 million years old — relatively young by geological standards.

Now a few contrarian scientists want to call time out. The canyon isn't 6 million years old, they say, but more like 70 million years old. If this order-of-magnitude challenge to the orthodoxy holds up, it would mean the Grand Canyon has been around since the days of T. rex.

"Our data detects a major canyon sitting there about 70 million years ago," said Rebecca Flowers, 36, a geologist at the University of Colorado and the lead author of a paper published online Thursday by the journal Science. "We know it's going to be controversial."

About that she is quite correct. Her research, which reconstructs the ancient landscape using a technique called thermochronology, is being met with a cool reception from veteran geologists who study the Colorado Plateau.

"It is simply ludicrous," said Karl Karlstrom, 61, a professor of geology at the University of New Mexico who has made more than 50 river trips through the canyon — one with Flowers, when she chipped her samples off the canyon walls — and helped create the Trail of Time exhibit for the National Park Service.

"We can't put a canyon where they want to put it at the time they want to put it," said Richard Young, a geologist at SUNY Geneseo who has been studying the Grand Canyon for four decades.

Wondrous though it is, Grand Canyon doesn't seem terribly mysterious at first glance. It's a gash in the landscape with a river at the bottom. The causality seems obvious. But Flowers and her fellow Old Canyon theorists say that what we see today in northern Arizona was originally carved, in large degree, by two rivers — neither of which was the Colorado River.

The western part of the canyon, they say, was largely incised about 70 million years ago by what has been dubbed the California River, which drained a mountain range to the west and flowed to the east, in the opposite direction from today's Colorado River. The eastern part of the canyon, they say, was created later, around 55 million years ago, by a different river.

Under the Old Canyon scenario, the Colorado River, which originates in the Rocky Mountains, is a bit of an opportunist, and about 6 million years ago took advantage of the pre-existing canyons and linked them in a fashion that creates the sinuous canyon of today.

The debate to some extent hinges on the semantic question of whether "an Ancient Grand Canyon" (as the Science paper calls it) is the same thing as the Grand Canyon of today. The Flowers paper says the depth of the ancient canyon was within a "few hundred" meters — roughly a thousand feet — of today's canyon.

Karlstrom warns that the Old Canyon theory threatens to confuse the park's 5 million annual visitors: "To them, it seems like dinosaurs might have lived with humans (like the Flintstones) and that geologists do not know if Grand Canyon was carved by the Colorado River or not (it was)," he wrote in an informal note crafted in response to the new paper.

Flowers began advancing the Old Canyon scenario in 2008, and the idea has been championed by Brian Wernicke, a geologist at Caltech.

"I see all the data as aligning very nicely for an Old Canyon model," Wernicke said.

Thermochronology studies the interiors of tiny crystals of phosphate minerals known as apatite. The crystals contain a record of uranium and thorium decaying into helium. If the temperature of the crystals is above 158 degrees, as would be expected in rock buried deep in the warm crust of the Earth, they retain no hint of helium. But if the rock has been cooler, below 86 degrees — as you'd expect if it was relatively close to the surface — the helium is abundant.

Scientists interviewed for this article believe the technique is a robust method for reconstructing ancient landscapes. But there are multi-fold objections to the interpretation advanced by Flowers and Wernicke.

The consensus estimate for the age of the Grand Canyon is based on multiple factors, including well-dated gravel deposits on the western mouth of the canyon where the river exits the Colorado Plateau and river sediments deposited into the Gulf of California.

The river incises the canyon at a known rate — about 150 meters per million years, or about the thickness of a piece of paper annually, Karlstrom said. The Old Canyon scenario doesn't claim that the Colorado has been grinding away in the canyon bottom for 70 million years, but it does require that ancient, abandoned canyons remain dry for long periods of time, Karlstrom said.

"Rugged topography like that fills in with erosion in way less than a million years," he said.

Professor Young, meanwhile, has an objection based on boulders and gravel that are found on the south side of today's canyon. They come from the cliff face of the Shivwits Plateau at the canyon's north rim. The material eroded from that cliff face at least 24 million years ago, Young said; in the years since, the cliff has receded to the north, and the Grand Canyon formed as the river ran along the bottom of the cliff.

In that scenario, there can't have been a canyon in that spot 70 million years ago; the boulder and gravel from the Shivwits cliff would have had to jump the canyon like Evel Knievel.

Young — who has spent more than 40 years studying another paleocanyon, the Hindu Canyon, which runs parallel to the Grand Canyon and is now filled with sediment — believes the new Flowers research is recording the gradual recession of the cliff, not the carving of a deep canyon.

"I think what's happened is the recession of the cliff is what's caused the cooling [of the minerals] to occur," Young said. "Their calculation is really measuring the fact that the surface was being eroded backward."

Joel Pederson, an associate professor of geology at Utah State, applauds the new paper, though he makes a semantic distinction when discussing the age of the Grand Canyon.

"They are looking at a really awesome precursor canyon that the Colorado River later in time took advantage of," Pederson said. "This new study really adds teeth to the realization that those paleocanyons, they were bigger and they were older than we thought they were."

But as for the age of Grand Canyon proper, Pederson is emphatic: "It is 6 million years old."

The Grand Canyon controversy is in many respects a case of science at its most vigorous, notwithstanding the grousing. Geologists have to find the narrative in landscapes that do not always speak clearly. The Grand Canyon provides a wonderful stratigraphic record, revealing sedimentary rock that formed hundreds of millions of years ago, but geologists struggle to discern the timing of the erosion that exposed the formations.

"Erosion's always been the toughest problem in geology," Wernicke said, "because what you're trying to study is all gone now."

As for why it matters at all — why we should care about when, and how, the canyon formed — Wernicke has a ready answer: "It's a fundamental question of human curiosity. It's about as basic a scientific thing as one can imagine."

Flowers will give a talk next Wednesday in San Francisco at the big fall meeting of the American Geophysical Union, as will her ally, Wernicke — and their critic, Karlstrom. Back to back to back.

Start your day with The Independent, sign up for daily news emails
PROMOTED VIDEO
Have you tried new the Independent Digital Edition apps?
News
ebooksNow available in paperback
Sport
Scunthorpe goalkeeper Sam Slocombe (left) is congratulated by winning penalty taker Miguel Llera (right)
football
Life and Style
A woman walks by a pandal art installation entitled 'Mars Mission' with the figure of an astronaut during the Durga Puja festival in Calcutta, India
techHow we’ll investigate the existence of, and maybe move in with, our alien neighbours
Arts and Entertainment
Sir Ian McKellen tempts the Cookie Monster
tvSir Ian McKellen joins the Cookie Monster for a lesson on temptation
News
i100
Travel
Tourists bask in the sun beneath the skyscrapers of Dubai
travelBritish embassy uses social media campaign to issue travel advice for festive holiday-makers in UAE
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
Independent Dating
and  

By clicking 'Search' you
are agreeing to our
Terms of Use.

iJobs Job Widget
iJobs General

Recruitment Genius: Partitioners / Carpenter / Multi Skilled Tradesmen / Decorator

£28000 - £50000 per annum: Recruitment Genius: Various opportunities are avail...

Recruitment Genius: Trade Marketing Manager

£25000 - £30000 per annum: Recruitment Genius: This company leads the market i...

Recruitment Genius: Financial Accountant - Part Time

Negotiable: Recruitment Genius: An exciting opportunity is available for a par...

Recruitment Genius: Domestic Gas Breakdown Engineers

£26000 - £30000 per annum: Recruitment Genius: Domestic Gas Breakdown Engineer...

Day In a Page

Jeb Bush vs Hillary Clinton: The power dynamics of the two first families

Jeb Bush vs Hillary Clinton

Karen Tumulty explores the power dynamics of the two first families
Stockholm is rivalling Silicon Valley with a hotbed of technology start-ups

Stockholm is rivalling Silicon Valley

The Swedish capital is home to two of the most popular video games in the world, as well as thousands of technology start-ups worth hundreds of millions of pounds – and it's all happened since 2009
Did Japanese workers really get their symbols mixed up and display Santa on a crucifix?

Crucified Santa: Urban myth refuses to die

The story goes that Japanese store workers created a life-size effigy of a smiling "Father Kurisumasu" attached to a facsimile of Our Lord's final instrument of torture
Jennifer Saunders and Kate Moss join David Walliams on set for TV adaptation of The Boy in the Dress

The Boy in the Dress: On set with the stars

Walliams' story about a boy who goes to school in a dress will be shown this Christmas
La Famille Bélier is being touted as this year's Amelie - so why are many in the deaf community outraged by it?

Deaf community outraged by La Famille Bélier

The new film tells the story of a deaf-mute farming family and is being touted as this year's Amelie
10 best high-end laptops

10 best high-end laptops

From lightweight and zippy devices to gaming beasts, we test the latest in top-spec portable computers
Michael Carberry: ‘After such a tough time, I’m not sure I will stay in the game’

Michael Carberry: ‘After such a tough time, I’m not sure I will stay in the game’

The batsman has grown disillusioned after England’s Ashes debacle and allegations linking him to the Pietersen affair
Susie Wolff: A driving force in battle for equality behind the wheel

Susie Wolff: A driving force in battle for equality behind the wheel

The Williams driver has had plenty of doubters, but hopes she will be judged by her ability in the cockpit
Adam Gemili interview: 'No abs Adam' plans to muscle in on Usain Bolt's turf

'No abs Adam' plans to muscle in on Usain Bolt's turf

After a year touched by tragedy, Adam Gemili wants to become the sixth Briton to run a sub-10sec 100m
Calls for a military mental health 'quality mark'

Homeless Veterans campaign

Expert calls for military mental health 'quality mark'
Racton Man: Analysis shows famous skeleton was a 6ft Bronze Age superman

Meet Racton Man

Analysis shows famous skeleton was a 6ft Bronze Age superman
Garden Bridge: St Paul’s adds to £175m project’s troubled waters

Garden Bridge

St Paul’s adds to £175m project’s troubled waters
Stuff your own Christmas mouse ornament: An evening class in taxidermy with a festive feel

Stuff your own Christmas mouse ornament

An evening class in taxidermy with a festive feel
Joint Enterprise: The legal doctrine which critics say has caused hundreds of miscarriages of justice

Joint Enterprise

The legal doctrine which critics say has caused hundreds of miscarriages of justice
Freud and Eros: Love, Lust and Longing at the Freud Museum: Objects of Desire

Freud and Eros

Love, Lust and Longing at the Freud Museum