Washington
Post: The Grand Canyon is generally believed to be only 6
million years old. A new study using a technique called
thermochronology claims the accepted age is off by an order of
magnitude. Thermochronology determines the history of rocks
based on their phosphate crystals. The crystals, known as
apatite, can trap the helium created by the decay of uranium
and thorium. If there is helium in the crystal, then the
crystals were formed near the surface. By collecting samples
from multiple sites and levels, scientists can determine how
long ago the crystals in the rocks formed. Rebecca Flowers of
the University of Colorado believes that the thermochronology
data her team has collected puts the age of the canyon at 70
million years, and that the canyon was cut in multiple stages.
The 70-million-year-old western section was carved by a river
flowing opposite the direction of the current Colorado River,
And the eastern section would have been carved by a second
river 55 million years ago. The Colorado joined the two
sections 6 million years ago. Flowers's theory is facing stiff
resistance from other geologists who believe that she is
misinterpreting the data she has collected and that the
evidence for the 6-million-year-old age is overwhelming.
