Figure 145: You Decide. Throughout this chapter, you have seen two conflicting perspectives: (1) the Colorado River carved the Grand Canyon after somehow penetrating the high Kaibab Plateau (shown by its green forests), and (2) Grand and Hopi Lakes breached their boundaries, carved the Grand Canyon and formed many surrounding terrain features, including the high, rapidly upwarped (via the water-balloon effect) Kaibab Plateau. Subsurface water then spilled out of the suddenly elevated Kaibab Plateau, down its steep slopes and eroded side canyons and valleys north of the river. As the Grand Canyon was cut deeper and deeper, subsurface water could also spill down the slopes on the south side of the river—a secondary effect that explains why more of the canyon lies north of the river. [See Figure 121 on page 219.] Also remember that the Grand Canyon extends 100 miles to the west of this picture.

Which of the above two perspectives fits the evidence? Could the Colorado River, which flows almost perpendicular to these side canyons and valleys, have carved them? Why are there no streams atop the Kaibab Plateau or the South Rim that discharge into these vast side canyons? What initially cut the channel through the Kaibab Plateau that allowed the Colorado River to flow from the bottom right of this picture northwest 45 miles? Was it the Colorado River or all the water spilling out of Grand and Hopi Lakes and the subsurface water draining out of the southwestern side of the rapidly upwarped Kaibab Plateau? Is the Colorado River the cause or a consequence of the carving of the Grand Canyon?