Theories for the Formation of Grand Canyon Sidebar 3

The Antecedent River Theory
The Antecedent River Theory states that the Colorado River was in its present course before the Kaibab Monocline formed. This theory says that the land raised gradually into the monocline, and as it raised, the river continued in its course, gradually eroding the Grand Canyon over 70 million years (Figure 2). This is the uniformitarian theory that is on the signs at the viewpoints along the rim of the Canyon, however, there are two basic, but serious problems.

Figure 2

Problems with the Antecedent River Theory:
First, there is no evidence of massive sediment deposition at the river's delta. By applying the rate at which the Colorado River erodes its riverbed now, we can extrapolate how much sediment we should expect to find after 70 million years. This extrapolation yields 1.8 million cubic miles of sediment (more than 1,500 times the volume of Grand Canyon sediment found) that should be west of the Canyon. Geologists have not found anything remotely close to this enormous amount of sediment.

The second problem with the Antecedent river theory is that after 70 million years of erosion, the Colorado River should have eroded far more sediment than it has. Applying the average rate of erosion to the overall length of the Colorado drainage basin yields an average depth of 7.3 miles in depth. Nowhere is there evidence that the river has eroded through several miles of sediment. Further, at the present average rates of erosion, it would only have taken the Colorado River 67,000 years to erode all the sediment from the Grand Canyon. "No matter how we consider present rates of erosion and the present form of the Colorado Plateau, we find it very difficult to imagine that the Colorado River drainage basin and Grand Canyon have an age of 50 to 70 million years" (Austin, 1994 p.89).

References
Austin, S.A. 1994. "How was the Grand Canyon Formed?" in The Grand Canyon: Monument to the Flood Institute for Creation Research, Santee. p. 83-110.

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