The more recent history of the Grand Canyon

The rocks exposed in the Grand Canyon record 2 billion years of Earth history, but the canyon itself is much younger.

Until recently most geologists estimated that the canyon formed 5 to 7 million years ago, based on radiometric dates on lava flows in the canyon.

Recently researchers from the University of New Mexico reported radiometric dates on cave deposits in the western part of the Canyon that indicated an age of 17 million years. These cave deposits are known to form near the water table. The water table dropped as the canyon carved its way downward, and caves formed early in the canyon’s history lie higher in the canyon’s walls than later-formed caves and have older deposits than caves lower in the canyon.

The new study should stimulate more research on piecing together the story of the canyon’s formation.

Source: Polyak, V., Hil, C., and Asmerom, Y., 2008. Age and evolution of the Grand Canyone revealed by U-Pb dating of water table-type speleothems. Science 319 no. 5868 p. 1377-1380. Free registration at the AAAS/Science website permits access to this article.

Or see this nice summary with great color photos (including the cave deposits shown above).