How Old is the Grand Canyon?

The Grand Canyon was formed over a long period of time by erosion and downcutting. Downcutting is the process by which a river cuts down into and erodes the layers of rock to form a canyon. According to the National Park Service, there are “[s]everal factors [that] increase the amount of downcutting that happens in Grand Canyon: the Colorado River has a steep slope, a large volume, and flows through an arid climate.”

Knowing that the canyon was formed by erosion, you may be wondering how exactly scientists can put a date on the absence of something. It’s easy to tell the age of the rocks that make up the canyon, but figuring out how long some of them have been missing is a trickier process that involves complex scientific methods, including a fancy geochemical technique that measures the temperature of rocks: “The deeper a rock is buried, the warmer it is. When erosion removes the overlying rocks, as when a canyon forms, the rock is moved closer to the surface and cools down” (Witze, 2014).

The complicated process of these geochemical techniques and differing interpretations of the data is largely responsible for the debate over the age of the canyon. Different geologists don’t fully agree on what the results mean and some are even using different temperature ranges, which affects the results. Geologists Rebecca Flowers of the University of Colorado Boulder and Kenneth Farley of the California Institute of Technology in Pasadena, for example, determined their results “assum[ing] that the ground temperature at the surface is 25 degrees Celsius, whereas [another] team used a range of 10‒25 degrees” (Witze, 2014).

These differing methods are part of the reason the date range hasn’t been  , but while their results may be different, there is some general consensus about the age of the canyon overall.

Research suggests that the Colorado River is estimated to have started eroding and downcutting the Grand Canyon at least 17 million years ago to as much as 70 million years ago, depending on who you ask and what section of the Grand Canyon you are asking about. But when did the downcutting “finish”?

The simple and most widely-accepted answer for when the Grand Canyon was eroded to its “current” recognizable state, and the one that’s included in the Trail of Time located at Grand Canyon National Park, is 6 million years ago. Some geologists, including Karlstrom—who has studied the Grand Canyon for over 30 years and helped develop the Trail of Time—suggest that “parts of the canyon could be tens of millions of years old”. In fact, Karlstrom estimates that some sections of the canyon are up to 70 million years old.

This doesn’t change the fact that the entire canyon, as it appears to us now, is much younger. So, even if there are sections of the canyon that were carved out 15-70 million years ago, they were not all connected by the Colorado River and did not form the Grand Canyon until a short 5-6 million years ago.

The Grand Canyon is an awe-inspiring piece of landscape, slowly carved away over time by water and other rocks. To stand in or on the Grand Canyon is to be humbled by its awesome scale, irreproachable beauty, complicated history, and age. Whether it is 5 million years or 70 million years old, the Canyon has certainly been here a lot longer than us and is worth seeing for yourself at least once.