Final answer:
The Grand Canyon was formed by erosion from the Colorado River over millions of years, not by glacial retreat. Geological evidence from the canyon's rock layers and faults, along with the long-term presence of the Colorado River, indicate a complex formation history much older than the last glacial retreat.
Step-by-step explanation:
No, the Grand Canyon was not created when the glaciers retreated. The formation of the Grand Canyon is primarily the result of erosion by the Colorado River over millions of years, rather than glacial activity. Glaciers did leave their mark on many landscapes across North America, as evidenced by features like Cape Cod, but the Grand Canyon's creation stems from different geological processes, including erosion and tectonics.
While some believe the Grand Canyon began forming only 5 million years ago with the Colorado River cutting through the rock layers, others propose it started around 50 to 70 million years ago in the Laramide. By examining the ages of the rocks and the faults that are cross-cut by the Colorado River, we can see evidence that supports its prolonged geological formation. For instance, layers of sediment from different geological periods, as well as tectonic activity, signal a complex history of formation predating any recent glacial retreats, which occurred around 12,000 years ago.
The Grand Canyon showcases erosion history, stratigraphy, fossils, rock formations, and volcanic deposits that range from 1,840 to 270 million years old. The presence of the Colorado River running through the canyon and the layered sedimentary rocks are evidence that the canyon was carved by the river over an extensive period, with ongoing erosion shaping it even today.