The Basin and Range Province is a vast physiographic region defined by a unique topographic expression. Basin and Range topography is characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins. The region covers most of the western United States, extends into northwestern Mexico and is mostly desert, as well as numerous eco-regions. The physiography of the province is the result of tectonic extension that began around 17 Ma (million years ago) in Early Miocene time. (http://en.wikipedia.org/wiki/Basin_and_Range_Province)
John Wesley Powell
Powell had two main concerns:
-
How had the Colorado Plateau and the Colorado River come about? How did nature work.
-
What were the possibilities for human settlement in an arid region?
- John Wesley Powell by James Aton
- John Wesley Powell River History Museum in Green River, UT
- John Wesley Powell Memorial Museum in Page, AZ
- Lost in the Grand Canyon, PBS film - Q143.P8 L67 2007
- Grand Canyon Explorer, Powell Expedition (includes chronology of 1869 trip)
-
The Powell Survey of the 1870s: Art & Science from the Saddle,
by John Weisher, 2009
Formation of Basin and Range topography by crustal extension:
A. No deformation has taken place.
B. Formation of listric normal faults.
C. Faults connect at depth forming horst and graben geometry.
D. Fault blocks form series of peaks and
Powell saw that water management—mostly for irrigation—would be a pivotal issue throughout the arid Southwest, one that state governments would be wrestling with forever. So he proposed state boundaries based on watershed, as seen on his map.
Map of the arid region of the United States showing drainage districts, 1890-91. Credit: Courtesy Dan Flores