Grand Canyon Geology

The Grand Canyon is well-known for its geological significance on our planet’s landscape, making it one of the most studied geological landscapes in the entire world. Its ancient rock sequence, that is so superbly preserved, offers us a window into the past. In fact, its 2 billion year history provides us with the ultimate geological learning playground as its formations, rock composition and landscape allows us to study things about the earth we may never have been able to otherwise.

The Grand Canyon, as we know it, is relatively young – a spry 17 million years old. Previous calculations estimated its age between 5 and 6 million years old until a 2008 study, published in Science, found the Canyon was actually quite a bit older. Opinions remained relatively split on the issue but one thing is certain – that a chasm as deep as the Grand Canyon could have appeared over so short a time and display the billions of years of rock that it does is somewhat mind boggling. While it sounds like a long time to us, it’s almost nothing in the life of the earth.

morning light at Grand Canyon, Arizona, USA

The Plateaus

The Canyon’s foundation was laid millions of years ago when the ocean covered Arizona and surrounding land. Water brought heavy sediment from all over and as it receded, left the sediment behind it. Tectonic plate movement and process of subduction shoved the land together creating the high plateaus of the region. Finally, the Colorado River sliced through the rock to create the depth of the canyon we see today. Its width is thanks to the erosion the ice age caused through the expansion and retraction of waters that pushed it apart giving it the step-wise topography we see today.

The region’s dry, arid climate contributed to forming the erosion of rock. The rock layers, a byproduct of the roaring river carving into the landscape, show us very early geologic history of the continent. They tell us stories we might never have known otherwise. It’s a lesson in the formation of the earth’s crust put beautifully on display thanks to the Colorado River.

Rock Formations

The stratification in the rock is literally a visual lesson in the geology of our earth. Eleven layers of the earth’s crust are visible from top to bottom and clearly defined. Most of these layers are made up of sedimentary rock, compressed sediment left behind by the water no longer there. It holds a wealth of information about our earth and what was happening at the time of its layer’s formation. Fossils tell stories of plant and animal life once found there. The two visible bottom layers are made up of metamorphic rock made by heat and pressure. Lastly, and not visible from every vantage point, there is one layer called a Supergroup. These are rocks that used to be sedimentary in formation but have morphed through heat and pressure into something different.

Today, nearly 40 rock layers have been identified within the walls of the Grand Canyon, beckoning students, scientists and geology enthusiasts to check them out. While you’d be hard-pressed to visit the Grand Canyon and not soak up a spectacular view, we’ve highlighted some of the more scenic geological views.

2 thoughts on “Grand Canyon Geology”

    • A good question without a very precise answer. The thickness of the crust under the Colorado Plateau (which encompasses the Grand Canyon) is 25-31 miles deep. The North Rim with its higher altitude is one of the thicker areas and probably runs close to 30 miles deep. It should be a bit thinner elseware. I suppose you would have to subtract mile if you were standing at the bottom of the Canyon.


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