A SKETCH OF THE GEOLOGICAL DEVELOPMENT 
OF THE PACIFIC SLOPE. 
BY GEO. F. BECKER.* 
The Pacific slope of the United States is the region the waters 
of which drain into the Pacific Ocean, or, in other words, the 
area west of the Rocky Mountains. It embraces not only 
Washington Territory, Oregon and California, but also Idaho, 
Nevada, Utah and Arizona, altogether about one-quarter of the 
area of the Union, excluding Alaska. This region presents 
marked peculiarities. It comprises most of the deserts of the 
United States and also some of the most fertile districts. It is of 
course famous for its mines which have yielded about 2,000 millions 
of dollars. The Pacific slope is particularly interesting to geolo¬ 
gists for many reasons. Its geology is much simpler than that of 
many regions, while the opportunities afforded for a study of the 
rocks are unrivalled. This is in part due to the great extent of 
desert country where but little vegetation and only a scanty soil 
mask the rocks. The deserts are barren because of the small 
rainfall, and it is partly owing to this cause that the Colorado 
River has cut the famous Grand Canon ; a ravine hundreds of miles 
in length with almost perpendicular walls in some portions over 
a mile in height. This is the grandest section through the strata 
of the earth’s surface known in the world. Many great geologi¬ 
cal facts which have been elucidated in Europe only after pro¬ 
longed and anxious investigation are illustrated in the simplest and 
most striking manner in the admirable exposures of the Pacific slope. 
This great region is by no means fully explored, but enough 
has been done by the various government expeditions to furnish 
material for such a sketch as I propose to offer. I may mention 
that the first purely geological expedition sent into this region by 
the general government was led by your townsman, Mr. Clarence 
King, then scarcely more than a boy in years. Much of the work 
now being done on the Pacific slope was also planned by him 
though executed under the directorship of Major Powell. 
It is the purpose of the present sketch to indicate the most im- 
♦Abstract of an address made to the Society, Sept. 3rd, 1SS6. 
