The distance between the cliff faces averages only 1000 feet (300 meters) at ground level.
One of the deepest parts of the Zion gorge is known as the Temple of Sinawava, a natural amphitheater with shear walls going down to a depth of 3,000 feet (900 meters).
Geology suggests that the canyon was formed through the Virgin River water erosion. But the water volume of the Virgin River is normally small, although flash floods and flooding does occur.
The canyon floor is surprisingly very flat.
The flat valley floor of modern Zion Canyon owes its origin to a 286 million m3 rock avalanche at 4.8 ka arising from the catastrophic collapse of a nearly 900-m-high wall of predominantly Navajo Sandstone Formation.
... Zion Canyon was blocked over a distance of 3.3 km, damming the Virgin River and creating a lake. At its high-stand, Sentinel Lake may have covered more than 6 km2, including all of Zion Canyon to The Narrows, but this water level was short-lived as incision of slide debris lowered the breach elevation to ~1345 m. There Sentinel Lake stood relatively stable for ~700 yr until filling with sediment.
Dynamics and legacy of 4.8 ka rock avalanche that dammed Zion Canyon, Utah, USA | The Geological Society of America (link to PDF)
How did the Virgin River remain flowing for a very long time (millions of years?) during what geology describes as uplift that pushed rock from sea level up to 10,000 feet?
Has water erosion created the Zion Canyon? How were The Narrows formed or not eroded wider?
How were the Three Patriarchs also eroded at their perpendicular angle to the main canyon direction?
Why are the top layers of the red Navajo Sandstone made of shale and other material? Could this material have been dumped or deposited at the same time as the material that dammed the canyon?