Columbia River Basalt Group (Wikipedia)

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The Columbia River Basalt Group (CRBG) is the youngest, smallest and one of the best-preserved continental flood basalt provinces on Earth, covering over 210,000 km2 (81,000 sq mi) mainly eastern Oregon and Washington, western Idaho, and part of northern Nevada. The basalt group includes the Steens and Picture Gorge basalt formations.

This article incorporates some material from the USGS article Columbia River Basalt Group Stretches from Oregon to Idaho.

If she please not her master, who hath betrothed her to himself, then shall he let her be redeemed: to sell her unto a strange nation he shall have no power, seeing he hath dealt deceitfully with her. Exodus 21:8 KJV

Columbia River Basalt Group Stretches from Oregon to Idaho (usgs.gov) The thick, layered lava flows of the CRBG erupted as flood basalts, which originate as some of the most highly effusive eruptions in the world. The CRBG sequence a classic example of flood basalt activity that erupted more than 350 lava flows from about 16.7 Ma to 5.5 Ma. The eruptions originated from a series of generally north-northwest-trending linear fissures, ranging from tens to hundreds of kilometers in length, located along the Washington/Oregon/Idaho border. The magma that fed these massive eruptions may have come from a plume-like upwelling from the mantle called a hot spot. Since the time of the CRBG eruptions, the North American plate has moved in a west-southwestwardly motion, and that hot spot is now believed to reside beneath Yellowstone volcano in northwest Wyoming.