Mountains of the so-called Basin-range type occur over a very much larger area of western America than is commonly supposed. They not only occupy the Great Basin country, but an expanse of territory ten times as vast. The desert ranges extend from the northern boundary of the United States southward far into Mexico. Throughout this great area they preserve intact all of their distinctive characteristics: more or less complete isolation of the ranges, abrupt elevation above the surrounding plains, lofty heights, short lengths, simplicity of structure, and the very resistant nature of their rocks. There are many other equally distinctive features which are not so conspicuous.
In accounting for the origin of the mountains of the Desert region, it was long believed that they were formed by simple normal faulting on a grand scale. This was the view first advanced by Gilbert,2 and it was generally adopted by the . . .