Final answer:
In the Grand Canyon, the oldest rock layers are found at the bottom and become progressively younger towards the surface, according to the Law of Superposition. The Great Unconformity marks a significant chronological gap, aiding in the study of the canyon's geological history and formation.
Step-by-step explanation:
The relationship between the age of rock layers and the depth at which they are found in the Grand Canyon is described by the Law of Superposition, which states that in undisturbed sequences of sedimentary or volcanic rock layers, the oldest layers are at the bottom and the layers become progressively younger as one moves upwards through the sequence. This principle is observed in the Grand Canyon, where sedimentary, metamorphic, and igneous rocks span from the Early Proterozoic to the Holocene. For example, at the bottom of the Grand Canyon, you can find the Vishnu Schist and the Zoraster Granite, which are among the canyon's oldest rocks, dating back to the Proterozoic Era. As one travels upwards or towards the rim, the rock layers become progressively younger with the creation of the Great Unconformity, a significant gap in the geological record that represents the passage of over a billion years. Understanding the stratigraphy of the Grand Canyon also contributes insights into its geological history, including hypotheses about the timing of its formation by the Colorado River, ranging from 5 to 70 million years ago.