The Great Unconformity represents a gap in time in the Grand Canyon and other parts of the world. It is a geological feature in which no rock layers are in the geological record dating back ...

Recent photograph of Grand Canyon from Walhalla Plateau, with the red line showing the Great ... [+] Unconformity between the metamorphic Proterozoic basement complex and the Paleozoic sediment ...

The proposed national monument also includes the “Great Unconformity,” a geological rarity that represents about 1.2 billion years of Earth’s missing history, within its boundaries.