1.2 Billion years are missing from the rock record of the Grand Canyon and it is called the Great Unconformity
The Grand Canyon has a 1.2 billion year gap in its rock record. This gap is called the Great Unconformity and is clearly visible with the, even to the naked eye.
Above the gap there is a sandstone layer that is 55 million years old and was deposited during the Cambrian age. During that time there were shelly ocean creatures, but no fish yet.
Below the gap there is a rock layer so ancient that it turned into gneiss. Gneiss is a typical rock type formed by regional metamorphism that happens when rock has been deeply buried and subjected to high temperatures and pressures.
The gneiss has been dated to be 1.75 billion years old! During that time bacteria were the most complex life on earth.
In between these two layers there are 1.2 billion years of Earth’s history that left no record behind in the Grand Canyon.
It could possibly be that it was an upland area for 1.2 billion years and therefore no deposits occurred. It could also be that it was underwater during part of the gap time, but then an uplift occurred and all of the regional Earth history was eroded away.
Either way, if you want to come face to face with the reality of deep time, visit Black Canyon where the Great Unconformity is easily reached with a short hike up the side of the canyon.