The San Juan Canyon, through which San Juan River runs, extends west across a high arid region in southeastern Utah and joins Glen Canyon of the Colorado near the southern boundary of the State. In 1921 I was attached as geologist to an engineering party which explored and mapped the San Juan Canyon for power and storage projects. The seven men comprising the party were under the leadership of K. W. Trimble, topographic engineer of the United States Geological Survey. They embarked on the canyon voyage in two small open rowboats on July 18 and reached Colorado River on October 3.
The journey of the Trimble party through the steep-walled chasm revealed a magnificent geologic structure section possessing the same dimensions as the canyon—133 miles long and as much as half a mile high. Although the vividly colored walls thus displayed the rocks and their structure in . . .