USGS INL Project Office
Research Drilling
The eastern Snake River Plain is a northeast-trending structural basin, 200 miles long and 50 to 70 miles wide, that occupies much of eastern Idaho. Currently accepted theories for the dramatic subsidence of the eastern Snake River Plain postulate that the plain has been subsiding in the wake of the Yellowstone hot spot caldera eruptions. The eastern Snake River Plain aquifer resides in the thick underground package of rocks and sediment that fills the upper part of this structural downwarp. The part of the basin occupied by the aquifer consists of basalt lava flows and sediment from nearby mountains and rivers. Rhyolitic ash flows and lava flows from the ancient calderas of the Yellowstone volcanic province are found below the base of the aquifer. Total depth of the eastern Snake River Plain structural depression is probably more than 16,000 feet. INL Core Methodology.
The Snake River Plain aquifer is hosted in complex layers of rock and sediment. Most of the rock is basalt erupted from shield volcanoes like those now found on the surface of the present-day eastern Snake River Plain. Basalt is a dark gray or black igneous rock erupted as lava and cooled on the surface of the earth. The eastern Snake River Plain aquifer occupies the upper part of these rocks; alteration almost completely seals off pore space in rocks at depth. The base of the eastern Snake River Plain aquifer is from 1,000 to 4,000 feet below land surface depending on the area.
For more information about eastern Snake River Plain geohydrology review our Fact Sheet (Orr, 1997) or Professional Paper (Whitehead, 1992).
Or visit the following sites for information designed for the general public:
- Yellowstone Volcano Observatory
- University of Utah
- Volcano World
- National Park Service
- Digital Atlas of Idaho
The USGS INL Project Office has its own drillers and drill rigs to drill and core new monitoring and research wells. We drill and core an average of two new wells every year; the INL contractor also drills and cores wells for research purposes. The core drilled from these new wells is archived at the Lithologic Core Storage Library (CSL) on the INL site, where it is stored and made available for scientists to study.
On the surface and in the subsurface of the eastern Snake River Plain, basalt and sediment layers vary in thickness from less than a meter to tens of meters. Basalt layers vary from solid rock or rubble; most sediment layers are unconsolidated. Basalt and sediment present unique challenges in drilling and core recovery. Only one well on the INL site, the 11,000 foot geothermal exploration well INEL-1, penetrates rhyolite.
Our scientists and drillers have developed techniques to obtain the best core possible in basalt, consolidated, and unconsolidated sediment.
