Origin of the Large Springs and their Alcoves along the Snake River in Southern Idaho

Abstract

A group of large springs, eleven of which rank among the largest springs in the United States, discharge 5,000 cubic feet a second from the north side of the Snake River between Bliss and Twin Falls, Idaho. Most of the water issues from pillow lava at the base of basalt flows that fill ancestral canyons of the Snake River carved in the older lake beds of the region. Six different canyon fills of basalt, indicating six displacements of the Snake River in Pleistocene time, have been mapped in this area by the author. Each of the flows that spilled into the Snake River Canyon caused a temporary lake on the upstream side of the lava dam and an alluvial fan containing huge blocks torn from the dam on the downstream side. Subsequent partial removal of the fans by the river has left concentrates of huge boulders in the form of trains, helpful in locating such displacements of the Snake River. Springs issue from these canyon fills of permeable basalt wherever the river has cut into them below the water table. Som...