At the Grand Canyon, the different phases of the geological wheel is clearly seen. In a way, the Grand Canyon provides a cross section of the planet’s history showing rocks that indicate the world’s environments unlike the one we see to-day. Peering down the rim one sees the remains of any landscape found on earth. The different layers vary from coarse to fine, as well as sandy rock and contain fossils of sea creatures as well as the imprint of ferns. It forms an unbroken record of life forms that had existed on this earth long before our time. It is a symbol of the American West and was protected as a national monument by Theodore Roosevelt in 1908 and is a UNESCO World Heritage site. The Canyon is also home to indigenous people Hopi, Zuni,Havasupai, Hualapai and Navajo tribes
Millions of people visit the Grand Canyon and in 2016 it had attracted more than 6 million tourists and contributed $ 904 million to the local economies and supported nearly 9,800 jobs. This spectacular chasm which provides the most fascinating landscapes is unique in its beauty. It has taken millions of years to provide this scene in terms of geological formation as we see it to-day. It is also a place where people have lived for many centuries and to the student of human history and geology, it provides untold avenues for study, all merged in mighty formations, mile after mile, and fantastic in height. The Grand Canyon through which the River Colorado flows across the state of Arizona is an awe inspiring creation of nature. The river is 278 miles in length with an average width of ten miles. The height of the stupendous walls vary from around 3,000 feet to 6,000 feet. The walls appear to be sculptured by erosion, evoking great fantasy, as is the brilliance of colours which change as the day begins and ends as the sun disappears between the innumerable escarpments and ravines.
Earth’s greatest geological showcase
It is the Colorado River which has carved the Grand Canyon out of the boulders during a span of time unimaginable. On this time scale, geologists consider the Colorado River to be a recent arrival which has scoured the Grand Canyon in less than five and a half million years. The rocks are ancient but the Canyon is young. In geological terms, the 5 to 6 million years is like a blink of an eye. A cross section of the Grand Canyon shows that it consists of at least twelve layers of rock. The types of rock which had been identified range from limestone rocks exposed within the Grand Canyon at the time it was formed 270 million years ago, to the oldest rocks within the Inner Gorge at the bottom, which date to 1.84 billion years. In comparison, geologists currently estimate the age of the earth at 4.5 billion years. The twelve different layers of rock have been formed during a period between, 270 million to 1.68 billion years, according to geologists. The Grand Canyon is described as the earth’s greatest geological showcase. Indeed, the different layers are so colourful; the depth, width and length so awe inspiring.
The head waters of the Colorado is nearly two miles above sea level which gives the river the intense velocity as it plunges to the Gulf of California, carrying with it hundreds of thousands of tons of sand and silt a day. The Grand Canyon is only one of the many canyons that the Colorado River has carved deep into the earth as it rushes to the sea. While the river deepens the canyon , the other forces make them wider. Resulting from the forces of nature the Grand Canyon has cliffs and other physical features. The process of erosion has created such fantastic shapes in rock, facilitated by the seasons, in that, during winter, the water that seeps between rocks which freeze at night and splits the rocks apart. In spring and summer, the melting snow and rains carry the boulders and gravel down the Canyon’s steep walls to the river leaving ridges. Thus , incredible formations on the rock surface extending mile after mile is seen by any visitor.
History as seen from the rim
Sediment which has got deposited layer after layer is now rock which reveals the geological history of planet Earth. This is clearly seen from the rim. Just as one sees fossils up on the Himalayas, one sees the imprints of sea creatures on these rocks, providing a glimpse into the life forms gone by. Sea creatures had thrived in this region 270 million years ago, before the Dinosaurs arrived. The exposed fossil bed is seen along the rim. What is seen is the result of the geological processes in progress all over the earth, namely, deposition, erosion and plate tectonics. Deposition is when water and wind deposit mud, sand and debris; plate tectonics is when intense heat within the earth slowly churns its mantle of rock which spreads, pushes, twists and lifts up plate like sections of the earth’s crust. This is familiar as seen in the last tsunami.
Erosion
At the Grand Canyon, the three events in the geological wheel deposition, erosion and plate tectonics is evident. It is understood that two billion years ago these rocks had not existed in the form in which we see today, but silt and sediments had built up the floor of the sea, sometimes mixing with lava and debris from volcanic eruptions and continuing the process for three hundred million years. Shifting of sections of the earth’s crust bwegan to compress the sea floor between sea shores. Extreme heat and pressure mixes and recrystallized the original sediments into rocks called schists. These formed great mountains and erosion during another three hundred million years, which have left pink and white granite rocks. Thus, rocks that are 1.8 billion years old form the base of the Grand Canyon.
Hence, the second stage of the geological cycle is over; erosion lasting a quarter of a billion years. The third cycle created the upper horizontal layers of the Grand Canyon as we now see exposed on the rim. This had begun five hundred million years ago, as the seas have advanced, retreated and advanced again, more than a dozen times. Sediments had formed layer upon layer on ocean floors, shorelines and swamps. As the environment changed from sea to dry land in the course of time, climate had also changed. The Canyon had also not been in the same position. It is known that what is Arizona as seen today was nearer the Equator three hundred million years ago. Silt had washed down to broad flood plains to the East. It is known that huge salamanders had waddled through swamps with luxuriant ferns where enormous dragonflies had been flying. Deposition in the equatorial climate and other physical features had also influenced the climate. For instance, what Rocky Mountains are today have prevented rain clouds from reaching the area causing vast dry dune fields over a period of two hundred and seventy million years, including the beautiful and fascinating layers of sandstone in the Canyon.
Evolution of life forms
The Canyon’s horizontal layers which had been deposited by the warm shallow seas had been abundant with marine life such as, fossils of corals, marine snails, shell fish, sponges and countless other examples of tribolites. They had endured for more than a quarter of a billion years, whereas, humans have existed as they are today, for about a hundred thousand years. The Grand Canyon’s rocks give us evidence of past environments of lost worlds, abundant with forms of life that had become extinct before the Dinosaurs. It is understood that around two hundred and fifty million years ago seas all over the earth had retreated devastating marine life called the Permian mass extinction, when perhaps, ninety percent of all marine creatures disappeared for ever. Deposition had continued and layers of limestone forms the rim of the Grand Canyon.
During their formation Dinosaurs evolved, flourished and had become extinct; their huge skeletal remains are seen in museums and places like Drumheller in Canada.
The Colorado Plateau which had been subject to erosion is half way through the stage of the third cycle and erosion will dramatically change the surface of the earth and catastrophic upheavals are likely to appear much faster as evidenced by unprecedented climate changes caused by human intervention like global warming among other destructive activity.
Evidence of habitation
People had lived at the Grand Canyon nine centuries ago and left evidence of their presence in small stone rooms by the Colorado. Broken bits of pottery and pictographs were left painted in rock shelters.
The Hopi, Zuni and other decedents of these ancient people had been called “Pueblo” which means ‘people’ in Spanish. The Pueblo people had lived throughout the Canyon farming near villages, hunting and gathering wild foods. To the Native American Hopi and Zuni people, the Canyon is a special place and the visitors numbering more than five million a year respect the Native American cultures.
The ruins and artefact are their heritage and they regard them with reverence. Hopi House at the Grand Canyon has captured the beauty of ancient Native American design and architecture and attracts visitors’ admiration.
The Grand Canyon National Park is itself enormous and rugged and a large number of archaeological sites numbering around 2,700 have been found, mainly of Pueblo people. They have occupied the Grand Canyon from about 800 AD to about 1200 AD. The early explorers, mainly the Spanish came here in search of gold and not to admire the splendour of the Canyon or the coloured landscape. The visitor to the Canyon today makes it a point to witness the setting sun in all its brilliance from any vantage point; Mather Point provides a spectacular view to be remembered always.
Prognostication
Man is not unlike any other creature that appeared and disappeared from the face of the earth millions of years ago. The massive forces of nature are too formidable for man to change the way he wants, but his actions can no doubt accelerate the natural processes, upsetting the delicate balance, causing calamities and catastrophes, much earlier than they are due to occur, according to the geological clock.
The geological clock began ticking some 4.5 billion years ago when the solar system was formed and planet earth cooled to form rocks and other features during the course of its existence when the environment had become right for life on earth. How hospitable planet Earth will be for man to exist and how long, will be determined by man’s actions alone.
The writer is a former Director,
Management Consultancy, N.I.B.M