View looking toward the
west with Bass Canyon entering from the left in the center foreground.
In Precambrian time, a fault at Bass Canyon dropped the strata to the
right (downstream) downward. This shows up today as a sudden
disappearance of the riverside cliff.
Shinumo Creek enters the river in the middle of the
“S” curves at the lower right. Shinumo Creek drains a large
area, and in the past its debris fan has pushed the Colorado River to
the left thereby forming the “S” curves.
The lack of a large debris fan at the current time would
indicate there haven’t been any large debris flows in recent
history. However, there is still enough debris left to partially dam
the river with the result that river gradient in this section is second
only to the Hance Rapid portion of the river. At some point in the past
(and possibly again sometime in the future) there was a major rapid
here.
In the upper right portion of the picture, the green area
represents the forested top of the Powell Plateau. The long ridge
extending to the left is Marcos Terrace. Walthenberg Canyon is directly
in front of it (before the river starts the long bend to the left), and
both Marcos Terrace and the walls of Walthenberg Canyon show the
classic massive cliff of the Redwall/Muav Limestones. (Note, both the
Belknap and Stevens River Guides incorrectly omit the “h”
in Walthenberg.)
Return to river
miles 96 to 104
Continue to river
miles 112 to 120
Return to the
Index Page for the Grand Canyon Tour
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