Grand Canyon Geology: Rock Superposition
Rocks tell us about colliding continents, meandering streams and volcanic eruptions. In the case of the Grand Canyon, the multi-layered strata provide insight to the age of the Earth.
Like a stack of pancakes, younger rock layers pile on top of older layers. We use the law of superposition to reveal Earth’s age.
For example, the base of the Grand Canyon are Precambrian basement rocks. These were formed from flowing magma which cooled and hardened about 1.8 billion years ago.
Most of the rocks on top are sedimentary like shale, limestone and sandstone.