Geologically speaking, Grand Canyon is considered to be a "young" feature, much of it having been eroded in just the last 5-6 million years. But the ages of Grand Canyon's rocks are a different matter entirely, spanning over 1.5 billion years of Earth's history. The oldest known rock in Grand Canyon, known as the Elves Chasm Gneiss, is located deep in the canyon's depths as part of the Vishnu Basement Rocks and clocks in at an ancient 1.84 billion years old. The youngest of Grand Canyon's rock layers, the Kaibab Formation, forms the rims of the canyon and is a mere 270 million years old. But that's still even older than the dinosaurs!

This interpretive exhibit along the Trail of Time discusses some of the methods geologists use to determine the ages of rocks, tools which are part of a field within the science of geology known as geochronology. This stop also offers an opportunity to actually see and touch a piece of the Elves Chasm Gneiss, the oldest known rock in Grand Canyon.