California & the Great Basin
The 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 "Golden Gate”.
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.
All map dimensions are approximate.