### Origin of the Grand Canyon
Two geologists present opposing theories regarding how the Grand Canyon in Arizona was formed.
Geologist 1
The Grand Canyon was formed rapidly, over a period of just a few weeks, by a single catastrophic flooding event. Approximately years ago, a large prehistoric lake located northeast of the canyon suddenly breached its natural dam. The sudden release of billions of gallons of water cut through the soft sedimentary rock layers, carving the entire depth and width of the canyon in a very short period.
Geologist 2
The Grand Canyon was formed gradually over millions of years through steady, continuous erosion by the Colorado River. Beginning about million years ago, the Colorado River began flowing through the region. As the surrounding Colorado Plateau was slowly uplifted by tectonic forces, the river steadily downcut into the bedrock. This slow process of water erosion, aided by wind and weathering, gradually shaped the canyon into its current form.
Based on the passage, Geologist 1 claims that the Grand Canyon was carved by which of the following processes?
- a single catastrophic flooding event over a very short periodCevap
- Bsteady, continuous erosion by a river over millions of years
- Ctectonic forces that directly split the bedrock apart
- Dlava flows from volcanic eruptions that filled a pre-existing valley