California and the Great Basin
Great Basin covers the vast interior portion of the intermountain West whose
rivers and streams do not reach the sea. Southeastern Oregon, Eastern
California, most of Nevada, Western Utah and Southeastern Idaho are included,
along with small areas of Wyoming. That’s the hydrographic definition, but
there are other more expansive ones: the physiographic, anthropological and
biogeographical definitions all extend further, especially to the south. The
name was coined by John Fremont, who had a gift for naming: he also gave us the
Great Basin in its present form developed around 2 million years ago, when the
rising Sierra Nevada and Cascade Ranges started blocking much of the moisture
off the Pacific. Its many internal ranges are largely the product of longer
term Basin-and-Range rifting, part of the tectonic process that is producing
the Gulf of California.
In geological time the Great Basin is brand new and its
hydrological definition might almost be called fleeting. In the human time
scale, it can be considered eternal.
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.
Small - Scale is 1:2 million or 1" = about 32 milesLarge
- Scale is 1:1.5 million or 1" = about 24 miles