The signature land form of the Great Basin is the fault-block range— a
broken piece of crust, tilted up as if hinged. The Sierra Nevada is by
far the largest, but the pattern is repeated again and again, all the
way across the Great Basin to its eastern edge. This is a symptom of the
expanding crust accompanying the continental rifting that has opened
the Gulf of California.
The Sierra is only a few million years old as a
range. Along with the resurgent Cascades to the north, it casts a sharp
rain and snow shadow that accounts for the Great Basin. Higher portions
of the California’s coast ranges have a similar effect. Like the
Cascades and Sierra, their western slopes are drained by abundant
rivers, their eastern slopes by few and mostly small ones.
Included on the map are all of
California and Nevada, almost all of Utah and Arizona, half of Oregon and
Idaho, some of Montana and Wyoming, along with smaller portions of New Mexico,
Baja California, and Sonora.
Dimensions: All map dimensions are approximate.