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Widening Canyon
This bend in the river marks a change in Zion Canyon scenery. From here downstream the canyon is growing wider.
A key factor is the different type of rock. In the canyon wall just above the river you can see the juncture where a darker mudstone layer emerges. As the river undercuts this looser mudstone, the hard santstone slabs above topple and wash downstream and the canyon wall recedes several feet. Look for scars in the cliffs where slabs have peeled away. Sometimes the attrition is gradual, but six river-miles downstream the Sentinel Slide is a large-scale example of a suddenly wider canyon.
Below the towering, erosion-resistant walls of Navajo Sandstone lies a weak formation of mudstones and siltstones called the Kayenta formation. Once the Virgin River begins to carve into the weaker Kayenta layer, erosion accelerates. The sturdy walls of Navajo Sandstone are undermined, and slabs fall into the river, widening the canyon.
During high water or after a heavy rain, you can hear the heavy cobbles clattering in the current. The river becomes a giant conveyor belt of gritty abrasives carving out the canyon |