The summit of the Kaibab is covered with peculiar pocket-like basins having no apparent outlets.

These were possibly glacial sinks, conducting away some of the surplus water from the melting snow and ice by subterranean channels.

It seems probable, therefore, that glacial flood-waters were an important factor in the formation of the canyons of the Colorado.

If this supposition is correct it would account, at least in a measure, for that distinct impression of arrested activity one receives from the present conditions obtaining there.* * Some canyon floors, where there is no permanent large stream, appear to have altogether ceased descending.

Dutton says of those which drain the Terrace Plateaus: "Many of them are actually filling up, the floods being unable to carry away all the sand and clay which the infrequent rains wash into them."-- Tertiary History, p.50.See also pp.
196 and 228 Ib.
The drainage at the edges of most canyons is back and away from the gorge itself.