The story of the Grand Canyon begins not with a river, but with a collision. About 1.84 billion years ago, long before complex life existed, chains of volcanic islands smashed into the edge of ancient North America. The immense heat and pressure from this impact forged the continent's foundation, creating dark, crystalline rocks. Today, these are known as the Vishnu Basement Rocks, and you can see them at the very bottom of the canyon's Inner Gorge. They are the first, oldest page in a stone book that is nearly two billion years old. The canyon matters because it allows us to read this book, to see a history of our planet that would otherwise be buried miles beneath our feet. But what stories were written on top of this foundation?
The Formation of the Grand Canyon
How the Grand Canyon formed: nearly two billion years of rock, a rising plateau and the Colorado River cutting down through it.
Chapter 1
The Foundation
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Frequently Asked Questions
How old is the Grand Canyon?
The canyon itself began to be carved by the Colorado River about 5.6 million years ago. However, the rock layers it exposes are much older, with the deepest rocks dating back nearly two billion years.
Why are there missing rock layers in the Grand Canyon?
This feature is called the Great Unconformity. It represents a time when up to 1.2 billion years of rock layers were eroded away by natural forces before new sediments were deposited on top, creating a massive gap in the geological record.
Is the Grand Canyon still changing today?
Yes, the processes that formed the canyon are still active. The Colorado River continues to carry sediment, cutting deeper into the earth at a rate of approximately 3 centimetres every 100 years, while the walls are gradually widened by the action of rain and ice.
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