Final answer:
The Grand Canyon likely started forming significantly only around 5 to 6 million years ago with the Colorado River's erosion, not 250 million years ago from tectonic plate collision. Geological evidence supports a more recent timeline, especially the Laramide Orogeny's role in uplifting the Colorado Plateau between 50 and 70 million years ago.
Step-by-step explanation:
The formation of the Grand Canyon is a complex geological event that was influenced by a number of factors over a vast period of time. While some believe the Grand Canyon began to form approximately 250 million years ago due to the collision of tectonic plates, current consensus among geologists suggests that the significant canyon formation began much later. The popular hypothesis states that the canyon's formation intensified around 5 to 6 million years ago, when the Colorado River began eroding the rock layers. However, the period known as the Laramide Orogeny, occurring from 50 to 70 million years ago, did contribute to the uplifting of the Colorado Plateau, which set the stage for later erosion by the Colorado River.
Studying the Grand Canyon's stratigraphy, including the faults and the ages of the rocks it has cut through, provides evidence in support of these more recent formation timelines. For instance, the canyon exposes sedimentary units ranging from the Proterozoic to the Holocene, with evident deformation such as faults and folds that occurred predominantly between 70 and 30 million years ago, ending with the uplift of the Colorado Plateau. Knowledge of the Grand Canyon's immense stratigraphic record, which does not align with the theory of plate collisions occurring 250 million years ago, supports the more recent formation hypotheses.