Grand Canyon National Park C onsidered one of the seven natural wonders of the world the Grand Canyon lives up to its title While the region contains a collection of varied rock formations that are impressive in their own right and contribute to its grandness it is the canyon or rather canyons that dominate and define the landscape The main canyon winds for 277 miles 446 km with a maximum depth of more than a mile 1 6 km and a maximum width of about 18 miles 29 km From this central canyon branches a maze of secondary gorges This enormous labyrinth of stone seems timeless but it is relatively young Earth has a history of nearly 4 5 billion years but it was only about 6 million years ago that the Colorado River and its tributaries began shaping the canyons While the shaping of land is a relatively new occurrence on Earth the Colorado Plateau Province the area of land into which the rivers carved is far more ancient This huge region covers more than 130,000 square miles 336,700 sq km and throughout time has experienced The age of the rock around the Grand Canyon varies significantly depending on its depth in the earth with the deepest layers of stone usually being the oldest This horizontal young-to-old layering is known as superposition In the deepest trenches of the Grand Canyon rock layers thought to be nearly 2 billion years old are visible Many of different geological movements from surrounding areas While areas around the plateau have cracked or been disrupted by movements within the earth the plateau generally remained intact maintaining a natural record of the planet’s history 10
This photo taken from an altitude of six miles 10 km shows the chasms that make up the middle portion of the Grand Canyon these base layers are made up of igneous and metamorphic rock Igneous rock is formed from rock that has melted and solidified again and metamorphic rock is created when previously existing rock is physically changed by extreme heat and pressure Vishnu Schist a metamorphic rock and Zoroaster Granite an igneous rock are among the region’s ancient rock layers each formed more than 1 5 billion years ago What happened during the next billion years is generally unknown because whatever rock was created has since eroded is now northern Arizona was at different periods of time the site of enormous sand dunes broad muddy rivers and shallow tropical seas A record of each period is now preserved in the form of sedimentary rock which is made of small sediments compressed together Over millions of years dunes became sandstone mud became shale and Over the course of the past 550 million years or so the area that 11
