Backward Drainage 49 
nial streams, with torrential floods each summer, compared with 
which anything that now comes down the Kanab would be a 
mere rivulet. The summit of the Kaibab is covered with pecu¬ 
liar 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 Col¬ 
orado. If this supposition is correct it would account, at least 
The Pink Cliffs. 
Southern end of High Plateaus. 
Photograph by J. K. Hillers, U. S. Geol. Survey. 
in a measure, for that distinct impression of arrested activity 
one receives from the present conditions obtaining there.* 
The drainage at the edges of most canyons is back and away 
from the gorge itself. The reason is that the rains cannot flow 
* 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. 
