When geologists determine that the Grand Canyon's sequence of rocks formed over hundreds of millions of years through deposition, mountain building, and erosion, they base their conclusion on the principle of ________, which states that ________.

When geologists conclude that the Grand Canyon sequence of rocks was formed through hundreds of millions of years of deposition, mountain building, and erosion, they are basing this conclusion on the principle of Uniformitarianism, which states that the present is the key to the past.

Uniformitarianism is a fundamental concept in geology, suggesting that the same natural processes observed today have been at work throughout Earth's history. By studying present-day geological processes and formations, scientists can interpret the past events that shaped the Earth's surface, including the deposition of sedimentary layers, the uplift of mountains, and the erosion of landscapes. The application of uniformitarian principles allows geologists to infer the long and complex history recorded in the rocks exposed in places like the Grand Canyon.