The Earth’s surface has so many different colors, features and forms that it’s not hard to understand why early scientists found it difficult to determine what was responsible for creating the natural landscapes that surround us. In the early 19th century, most European scientists believed that earthquakes and volcanoes were the primary forces that shaped our planet’s geology, from the highest mountains to the deepest valleys, and to the vast open spaces that lie between.
But in 1858, an American geologist named John Strong Newberry changed that thinking after he arrived in the Grand Canyon on a surveying expedition for the U.S. government. At the time, the Grand Canyon didn’t even appear on many maps. It was part of a region written off simply as “the great unknown.”
At 277 miles long, up to 18 miles wide and more than a mile deep into the Earth’s crust, the Grand Canyon almost defies belief. All the waters in all the world’s rivers would only fill it halfway. The great gorge exposes the very interior of the North American continent; each rock layer reveals a story about geologic history, from the present day to almost 2 billion years ago.
John Newberry was the first geologist ever to descend down to the Grand Canyon’s floor. Once he set eyes on the Colorado River and studied the colorful layers of rock that towered above him, he proposed that the river itself had carved the canyon—a radical theory for the time. It suggested that it would have taken millions of years to carve the canyon, which meant that the world was much, much older than most people had imagined.
Today, most scientists agree that Newberry was right about how the canyon was formed. But the tale begins even before the Colorado River first began flowing down and out of the Rocky Mountains about 6 million years ago. In fact, it starts hundreds of millions of years ago.
Evidence: fossils on top
Two-hundred-and-fifty-million years ago, the Grand Canyon started to form as the result of a collision between the Pacific and North American tectonic plates. They bumped together with such force that the North American plate thrusted up more than two miles.
Then, over a period of 15 million years, what was once seabed continued to rise until it formed a vast plateau far above sea level. Today, it’s possible to find fossils of ocean creatures deposited in a Permian seafloor 7,000 feet up, at the top of the Grand Canyon.
The plateau stayed that way for millions of years—until water transformed it.
Proof: water down below
Six million years ago, several hundred miles south of what is now the Grand Canyon, tectonic plate movements opened up the Gulf of California to the sea. For the first time, small streams in the Rocky Mountains could empty into the Pacific Ocean. These streams merged to form the Colorado River, which, as it headed to the Gulf of California, naturally sliced through the lands that were to become the Grand Canyon.
In truth, though, the Colorado River is not very wide as rivers go: the Amazon River (parts of which, during the rainy season, can exceed 24 miles in width) and the Volga River in Russia (40 miles wide) exceed it by far, and yet they’ve never made anything similar to the Grand Canyon.
The Colorado River, however, drops 10 feet for every mile it travels, and it carries half a million tons of sand, silt and rocks downstream every day. It’s almost like liquid sandpaper. Rain and ice also play a part, chipping away at the canyon walls. Such detritus is also carried downstream; fossils and rocks from this area have even been found almost as far away as the Gulf of California.
Watch the video clip below, produced by Naked Science and taken from a longer documentary titled Colliding Continents. While continental drift helped sculpt one of the world’s most recognizable landmarks, it was the liquid and fluid fingers of an artistic river that finally produced the exquisite results we have today.
Here’s to finding your true places and natural habitats,
I can relate to this river, Candice, not only because of being a native Coloradoan but it’s influence to the West; a very needed source of water. Thanks.
That’s terrific to hear, Richard! And, February 26, was the Grand Canyon’s 100th birthday, another source of pride for the West. —C.G.A.
In an nice bit of synchronicity, NASA’s Earth Observatory just published a nice page (with terrific photos) on the Grand Canyon in their Earth Matters blog:
Those photos are pretty impressive. Thanks, Joan! —C.G.A.