[carumba]

Vertical walls of Marble Canyon. No rubble lying at the low valley floor built up to a height one would expect from eons of erosion over time. Evidence of a large inland sea in southern Utah. Why would anybody believe that the Grand Canyon was a cataclysmic flood instead of a gradual slow erosion process?

[patton]

Ummmm...because it makes sense?

[mhx]

A lot of people have a religious belief that it must have been a fast process.

[LexBaird]

Vertical walls of Marble Canyon. No rubble lying at the low valley floor built up to a height one would expect from eons of erosion over time. Evidence of a large inland sea in southern Utah.

There is geological evidence that prehistoric Lake Bonneville drained north in a cataclysmic flood into the Snake River, via Cache Valley and the Portneuf Gap.

[dr_lew]

The Grand Canyon follows a meandering course and has a dendritic ( tree-like ) system of tributary canyons. It was clearly formed by a gradual erosion process.

Compare and contrast the "braided stream" appearance of the Spokane Scablands, caused by the scouring action of a catastrophic flood.

[LexBaird]

Evidence of a large inland sea in southern Utah.

Lake Bonneville drained north, via the Snake River. Plenty of suddenly scoured canyons along that path: Portneuf Gap, Snake River Canyon, etc.