when did the grand canyon start to form
Grand Canyon The Grand Canyon is part of the Colorado River basin which has developed over the past 70 million years,[12] in part based on apatite (U-Th)/He thermochronometry showing that Grand Canyon reached a depth near to the modern depth by 20 Ma.[13] A recent study examining caves near Grand Canyon places their origins beginning about 17 million years ago. Previous estimates had placed the age of the canyon at 5â€“6 million years.[14] The study, which was published in the journal Science in 2008, used uranium-lead dating to analyze calcite deposits found on the walls of nine caves throughout the canyon.[15] There is a substantial amount of controversy because this research suggests such a substantial departure from prior widely supported scientific consensus.[16] In December 2012, a study published in the journal Science claimed new tests had suggested the Grand Canyon could be as old as 70 million years.[17] However, this study has been criticized by those who support the "young canyon" age of around six million years as "[an] attempt to push the interpretation of their new data to their limits without consideration of the whole range of other geologic data sets."[14]