A brief summary of the Columbia River Flood Basalts
The Columbia River Flood Basalts in the northwestern US were created when the Yellowstone Hotspot and the associated mantle plume created a massive outpouring of basalts in a relatively short period of time. There is much debate as to what part of the earth contributed to creating the basalts. Although no one has come to consensus, evidence points to a mantle plume source that was contaminated by crustal material. As the plume caused molten mantle material to rise through the earth, it formed pools or reservoirs in the lower crust. Some of the crust material was added to the plume material and changed the composition of the magma. This composition can be analyzed and compared to other lavas erupted in other parts of the world. Specifically, radiogenic isotopes can shed light on the history of a magma. In summary, The earliest units of the Columbia River Basalts were created by a mantle plume. The youngest unit was created when the subcontinental mantle lithosphere melted after being heated by the mantle plume for 3 million years.
For more indepth information on radiogenic isotopes and the Columbia River Flood Basalt controversy, click here.