There is no doubt that the Grand Canyon is exactly that—grand. That word is used too often to describe features that are far from grand. But in this case the description not only fits—it is an understatement. As Heidinger said, “Some of nature’s finest work is here on display, created by her artists: water, wind, and time.”
John Muir, one of my heroes, said that this about the Grand Canyon
“It seems a gigantic statement for even nature to make, all in one mighty stone word, apprehended at once like a burst of light…coming in glory to mind and heart as to a home prepared for its from the very beginning.
Wildness so godful, cosmic, primeval, bestows a new sense of earth’s beauty and size. Not even from high mountains does the world seem so wide, so like a star in the glory of light on its way through the heavens.
…Here, for a few moments at least, there is silence, and all are in dead earnest, as if awed and hushed by an earthquake.”
President Theodore Roosevelt said that it was “the one great sight which every American should see.” Elizabeth Browning’s brief but profound remark, “Earth is crammed with heavens.”
Each year I have gone to Arizona I have tried to learn a little more about geology. There is no better place to learn about geology. The Grand Canyon is that deep gash which an early runner of the river called a “dark and mysterious cleaving, actually stretches from 600 feet to 18 miles depending on where you find yourself. And that gash exposes nearly two billion years of the earth’s history visible in its distinct layers. Juanita Brookes quipped about the gash, “What God hath put asunder let no man join together.” The natural forces of running water, heat, frost, gravity, abrasion,upliftand faulting all worked together at different times to carve this astounding chasm. As one looks down into that canyon one looks at nearly 2 billion years of the earth’s history written out in a colorful palette of different colors each representing a different age. John Muir called it a“grand geological library, a collection of stone bookscovering … tier on tier conveniently arranged for the student.”
Its “layer cake geology” reveals years of stratified rock in chronological sequence. The younger rocks are above and the older ones lower. In the upper layers one can find evidence of ancient rich marine life. Deeper and hence older layers of Vishnu Shist do not reveal any former life at all. Marine deposits were laid down over 45 million years ago when a clear sea formed resistant Redwall limestone . Muav limestone in front of the redwall formed in shallower seas and late eroded in gentle patterns of cliff and shapes and ledges.
At the bottom of the canyon there are remnants of Precambrian rocks that are nearly 2 billion years old. The processes that triggered the immense canyon started about 1.68 to 1.840 billion years ago. At that time enormous continental tectonic plates moved slowly across the surface of the earth. Then a plate that carried island arcs and the plate that became North America collided. Heat and pressure from this process changed the existing rocks into dark metamorphic rock that can now be seen in the basement of the canyon. The oldest rocks are at the bottom.Molten rock then squeezed into cracks and hardened as light bands of granite.
About 70 million years ago the Rocky Mountains began to form, and the Colorado Plateau rose up as the North American plate pushed up the Rockies Mountains and the plateau when that plate overrode the Pacific Plate underneath it. In the process a large part of what is now Utah, northern Arizona, western Colorado and a corner of northwestern New Mexico slowly rose up from the sea level to elevations of thousands of feet. The Plateau is about 130,000 sq. miles in size. That is how the ocean floor close to modern day California ended up so high! These powerful geological forces created both the Rockies and the Colorado Plateau. This was how the Colorado Plateau was created. This rising up occurred with very little tilting or deformation of the sedimentary layers.
But the sculpting of this natural work of art was not done. After that the Grand Canyon was carved. About 5 or 6 million years ago, the Colorado Riverflowed across the Colorado Plateau on its way to the Rocky Mountains and ultimately to the Gulf of California. Each rain washed sparsely vegetated desert soils into the river. There was little to hold the soil together. A steep gradient and heavy sediment loads created a powerful tool for erosion.
The process of erosion was assisted by rain, snowmelt, and tributary streams that entered the canyon throughout its length. Windwas also influential. That wind has been called the greatest sandblasting machine on earth. The volume of the Colorado River varied greatly from year to year. When the last Ice Age ended some 12,000 years ago, the Colorado River may have had a flow 10 times what it is today! As the river cut down into the canyon the canyon deepened.
The fact is of course that the rocks of the Grand Canyon are not unique, but the clarity of the exposure geological record is unique. So it possible to read that history in the rocks. It was a fantastic example of what Chris and first heard in Grosse Morne National Park in Newfoundland—there is a lot of history to be learned from rocks. As my guidebook said,
“Grand Canyon’s mulitcolored layers of rock provide the best record of the Earth’s formation of anywhere in the world. Each stratum of rock reveals a different period in the Earth’s geological historybeginning with the earliest, the Precambrian Era which covers geological time up to 570 million years ago. Almost 2 billion years of history have been recorded in the canyon, although the most dramatic changes took place relatively recently, five to six million years ago,when the Colorado River began to carve its path through the canyon walls. The sloping nature of the Kaibab Plateau has led to increased erosion in some parts of the canyon.”
Ultimately that is what the Grand Canyon experience is all about—an appreciation of immense amounts of time. Geology is the science that deals with immense time. James Hutton considered by some to be the founder of modern geology wrote a grand opus on the topic. His main theses were very controversial at the time, though they are universally accepted now. The first was that the Earth’s surface is constantly being eroded by water, ice, wind which together grind old rock rock into smaller chunks, pebbles and fine sediment. These are then carried down stream by rivers and eventually are deposited in the bottom of the sea. Then those sea bottoms are transmogrified slowly by pressure and heat from below and then become stratified into layers of new rock. That heat also causes uplift of those strata and of the magmas of molten rock beneath them that eventually form jagged mountains, domed plateaus, and grantic knobs, great rifts, warpings, and exposures and juxtapositions of variously tilted strata. Those of course are then eroded all over again. As David Quammen explained it,
“in short, mountains become silt which becomes sedimentary rock which becomes mountains, with erosian driving the process from above and subeterranean heat driving it from below,in a repeating cyclethat seems to go on indefinately, ‘showing no vestigage of beginning,–no prospect of an end.’
As John Muir said, the world, though made, is yet being made. That this is still the morning of creation. That mountains, long conceived, are now being born, brought to light by the glaciers, channels traced for rivers, basins hollowed for lakes. ”
He also said,
“Everybody needs beauty as well as bread, places to play in and pray in, where Nature may heal and cheer and give strength to body and soul and alike.”
After all, J.B. Priestly had said this about the Grand Canyon in Harper’s Magazine,
“There is of course no sense at all in tyring to describe the Grand Canyon. Those who have not seen it will not believe any possible description. Those who have seen it know that it cannot be described… It is not a show place, a beauty spot, but a revelation. The Colorado River made it; but you feel when you are there that God gave the Colorado River its instructions. The thing is Beethoven’s Ninth Symphony in stone and magic light. I heard rumors of visitors who were disappointed. The same people will be disappointed at the Day of Judgment.”