Tyrannosaurus Rex may have once hung out in the Grand Canyon. A
new study suggests the western portion of the canyon may be 70
million years old and may have been carved by an ancient river;
previous estimates suggest the canyon is just 6 million years
old. Scientists from the University of Colorado took rock
samples from the bottom of the western part of the canyon and,
using a phosphate-based mineral known as apatite, were able to
date the bottom of the western part of the canyon to 70 million
years ago. The process is called thermochronometry and uses the
thermal history of minerals taken from the bottom of the Grand
Canyon compared with rocks that lie several miles beneath the
Earth's surface. "Rocks cool as they approach the Earth's
surface by erosion, and [apatite] records this cooling history,"
the report says. "Data from the western Grand Canyon suggested
excavation to within several hundred meters of the canyon's
modern depth by [70 million years ago], in direct conflict with
the young canyon model."