When rafting down the Colorado River through the Grand Canyon, a side canyon often stopped at and explored is Blacktail Canyon. The canyon is primarily part of the Tapeats formation of layered rocks, which gives it a great deal of wonderful character. Towards the back of the canyon however, the bottom of this layer begins to become exposed to reveal the older layers below it. However instead of being the expected rock layers related to the Unkar Group, we instead find layers of Vishnu Shist below it, which are over a billion years older than the Tapeats above! Where did over a quarter of the Earth's history disappear to?