Boundary of the eastern Snake River Plain (ESPR), Idaho.
The ESPR is a structural basin that extends about 200 miles in a northeast direction and is 50-70 miles wide.
The basin is bounded by faults on the northwest and by down warping and faulting on the southeast.
It has been filled with basaltic lava flows interbedded with terrestrial sediments.
The combination of basaltic rock and sedimentary deposits forms the ESRP aquifer,
which is the primary source of groundwater in the basin