The Columbia River Flood Basalts were produced by a warm mantle anomaly. Evidence points towards a mantle plume. The Yellowstone hotspot seems to fit the temporal evolution of basalts in the area. The heating caused a rapid and voluminous outpouring of basalt tholeiites.
There is still no definitive “answer” as to the source of CRFB’s between scientists working on this problem. However, the data seem to point towards varying sources for the three different groups of basalt flows. The oldest group, comprised mainly of the Picture Gorge Basalts, has an asthenospheric mantle source with a small degree of crustal contamination. The main volume of the CRFB is found in the Clarkston Group, with the largest flow being the Grande Ronde Basalt. This group has a mantle plume source with crustal contamination. The youngest group, the Saddle Mountains Basalt varies distinctly from the earlier flows. It represents melting of the SCML after it has been heated for 3Ma+ by the mantle plume.