A study from the University of Colorado Boulder has determined the Grand Canyon in Arizona to be over 60 million years older than previously thought. The research, which was conducted by CU-Boulder assistant professor Rebecca Flowers, says the geographic landmark was created 70 million years ago while dinosaurs were still alive.
To determine the birth date of the Grand Canyon, Flowers and her colleagues tested a number of mineral grains found at the bottom of the west part of the canyon. According to Flowers, her research team then applied a dating method to the mineral grains. The method looked at a phosphate mineral called apatite and determined the radioactive decay of uranium and thorium atoms into helium atoms in the sample.
In the end, Flowers’ research determined the Grand Canyon is much order than previously thought. “Our research implies that the Grand Canyon was directly carved to within a few hundred meters of its modern depth by about 70 million years ago,” she said. Flowers’ team along with Kenneth Farley, a professor at the California Institute of Technology, recently published their findings in Science.
This new data adds to the controversy over the exact age of the Grand Canyon. Many scientists believe the famous canyon was not created all at one time, but rather carved out in segments at separate times, eventually morphing into the geological site seen today.
In 2008, Flowers had previously estimated that parts of the eastern Grand Canyon were developed as far back as 55 million years ago. The new study shows that some parts of the canyon may be even older.
“An ancient Grand Canyon has important implications for understanding the evolution of landscapes, topography, hydrology and tectonics in the western U.S. and in mountain belts more generally,” Flowers said.
Flowers said helium is held in the rocks of the Grand Canyon when the temperature of the apatite grains is higher than 158 degrees Fahrenheit. Below 86 degree, and the helium is lost from the apatite mineral grains. “The main thing this technique allows us to do is detect variations in the thermal structure at shallow levels of the Earth’s crust,” she said. “Since these variations are in part induced by the topography of the region, we obtained dates that allowed us to constrain the timeframe when the Grand Canyon was incised.”
The quest to find the age of the Grand Canyon is not over, however. For years scientists have been arguing about the subject. Most believe a study that looked at gravel from the stream in the canyon, which estimated it to be 5 to 6 million years old. Yet another report said the canyon was 17 million years old based on studies done on minerals found in caves in the canyon walls.
Flowers believes she knows why scientists are so interested in the age of one of America’s most popular landmarks. “There has been a resurgence of work on this problem over the past few years because we now have some new techniques that allow us to date rocks that we couldn’t date before,” she said.