Origin of the Snake River Plain
The origin of the Snake River Plain is attributed to several geologic processes. The Snake River Plain is divided into Upper (eastern Snake River Plain) and Middle (western Snake River Plain) segments on the basis of geology and hydrology.  The eastern Snake River Plain is underlain by volcanic rock (primarily basalt with lesser amounts of rhyolite) and relatively thin layers or lenses of sedimentary material that thin towards the center of the basin. Prolific amounts of water can be withdrawn from the aquifer associated with the eastern Snake River Plain.  The repetitive sequence of successive basalt flows that make up the aquifer provide favorable hydrologic conditions for water to easily move through the system.  Transmissivity values (a measure of the ability of water to move through a volume of material) associated with the eastern Snake River Plain aquifer are generally one to two orders of magnitude greater than those determined for the aquifers in the western Snake River Plain (Lindholm, 1996).

The western Snake River Plain is underlain by a section of sedimentary material that may be in excess of 5000 feet thick in the central portion of the basin. The generally fine grained nature of the sedimentary material does not allow water to move as freely as observed in the eastern Snake Plain (Newton, 1978).

Information supplied by Idaho Water Resource Research Institute, University of Idaho December 1998
Authors: Dr. Gary Johnson, Donna Cosgrove, and Mark Lovell.
Graphics: Sherry Laney and Mark Lovell
All State of Idaho images and graphics created with GIS files obtained through Idaho Department of Water Resources Public Domain GIS unless otherwise noted.
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