This subsidence of the crust produced a large, slightly depressed lava plain now known as the Columbia Basin or Columbia River Plateau.The northwesterly advancing lava forced the ancient Columbia River into its present course.The Latah Formation sediments of Washington and Idaho are interbedded with a number of the Columbia River Basalt Group flows, and outcrop across the region.
The Columbia River Basalt Group is thought to be a potential link to the Chilcotin Group in south-central British Columbia, Canada.
The Columbia River Basalt Group flows exhibit essentially uniform chemical properties through the bulk of individual flows, suggesting rapid placement.
Ho and Cashman (1997) characterized the 500 km (310 mi)-long Ginkgo flow of the Columbia River Basalt Group, determining that it had been formed in roughly a week, based on the measured melting temperature along the flow from the origin to the most distant point of the flow, combined with hydraulics considerations.
The various lava flows have been dated by radiometric dating—particularly through measurement of the ratios of isotopes of potassium to argon.
Major hot-spots have often been tracked back to flood-basalt events.