SCIENCE

To the untrained eye, the Grand Canyon might just look like one big hole in the ground. But to some scientists, the American Southwest’s iconic gorge is increasingly looking like several ancient canyons of different ages, stitched together by erosion. (National Geographic News)

Use our resources to color-code the Grand Canyon’s ages.

Discussion Ideas

• Look at our cool coloring page of the Grand Canyon. The Fun Fact says “The oldest rocks in the Grand Canyon are almost two billion years old.” The Nat Geo News article says the oldest parts of the Grand Canyon are only 70 million years old. What’s going on here?
  • The Nat Geo News article is about the age of the canyon itself—the deep, steep valley carved in rock. Our coloring page gives you a fast fact about the age of the rocks that make up the Grand Canyon. The rocks were around for a long, long time before they started eroding!
• Read through our encyclopedic entry on canyons. The entry describes three major factors that contribute to the formation of large canyons: rivers, erosion, and tectonic uplift. Which of these factors contributed to the formation of the Grand Canyon?
  • All three!
    • Ancient rivers, most recently the Colorado, have helped carve the Grand Canyon.
    • The canyon has been eroding for between 6 million and 70 million years.
    • The Grand Canyon is carved into the Colorado Plateau. The Colorado Plateau is a large area that was elevated through tectonic uplift millions of years ago.
• Have people had an impact on the formation of the Grand Canyon? How?
  • Yes, human activity is impacting the Grand Canyon as we speak. The Colorado is one of the most dammed rivers in the world. Dams prevent the natural flow of sediment from the river and disrupt natural erosion patterns.
• The geology of the Grand Canyon is one of the most studied in the world, and there’s a wealth of fantastic resources.
  • For ambitious geologists out there, check out Wikipedia’s gorgeous, gorgeous featured article on “Geology of the Grand Canyon area.” (Vishnu schist! Zoroaster granite! Geology is for poets!)
  • The good folks at the National Parks Service have a terrific collection of instructional content on Grand Canyon geology. This simple collection of timeline cards helps puts the Nat Geo News article in perspective.