CBSE Class 10 Answered

The specific geologic processes and timing that formed the Grand Canyon spark lively debates by geologists. Around 20 million years ago the Colorado River began to carve into the Grand Canyon at its eastern end. Extensive carving of the plateaus allowed for the detailed study of the Earth's movements. Processes of stream erosion and vulcanism played a major role in the formation of Grand Canyon.

Helium is produced by the decay of radioactive uranium found within a type of calcium phosphate mineral called an apatite that layers the walls of the Grand Canyon. When the apatite gets too close to the Earth’s surface, its temperature decreases and helium can no longer escape from the rock through diffusion. Thus the amount of helium found in the rock layers offers clues as to that rock’s temperature history or when that rock reached the surface and thus when that portion of the Grand Canyon was formed.