Keywords: flood basalt, delamination, mantle tomography

The Columbia River flood basalt eruptions began where they ‘‘should’’, but very quickly migrated far off track as they grew in intensity, and an impressive topography emerged in eastern Oregon. All this, I will show, is a result of several lithospheric gravitational instabilities that pre-existed and were triggered by Yellowstone plume arrival. This includes a delamination of Farallon ocean lithosphere previously abandoned flat against the region, a foundering of the Wallowa batholith root, and gravitational collapse of an elevated and weakened eastern Oregon lithosphere.

Flyer: Seminar_Humphreys_2023