Figure 146: Looking south at the Bright-Angel Fault.  Note the vertical offset of the two broken segments of the prominent Coconino Sandstone Layer. Imagine the gigantic force required to fracture horizontal slabs of thick rock along an inclined plane whose edge is marked by the dashed yellow line. The fracture extend some distance into the South Rim of the Grand Canyon (in front of the camera), and 60 miles to the north behind the camera!

Now try to imagine a 300-mile-long train loaded with the weight of 2,800 cubic miles of dirt (that had been eroded to form the Grand Canyon) plus enough water (equal to the volume of two Lake Michigans and one Lake Huron) to transport that dirt 400 miles far out into the Gulf of California.

The train is traveling west along the path the Colorado River flows today. The depressed ground below that heavy train springs back up when the heavy train “spills” over the western edge of the Colorado Plateau that centuries earlier was lifted more than a mile. For every pound of dirt and water that spilled over that western edge, an additional pound of upward force acted to shear the slab and produce the fault. That rebound and the vertical vibrations were greatest at the western edge of the Plateau, so the horizontal slab is fractured (sheared) along the dashed yellow line, and the west side of the fault is lifted 200 feet higher than the east side of the fault. This dramatic fault and the break and offset of the Coconino Sandstone are easily seen from most of the North Rim.

Figure 147: 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 218.]  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?  Why does most of the Grand Canyon lie on the north side of the river?  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?