[Heatseeker]

This does seem to be what may have happened 17 mya when an impactor struck SE Oregon causing the volcanism that created the Snake River and Columbia Basalts and the hot spot that has now migrated to under Yellowstone Park.

Coming in a bit late, but do you have a source for this? It sounds fascinating.

Though I'm still sad that any discovery of such a large impact site means "my" impact crater drops a spot in the world size ranking. ;)

[Mike Darancette]

The Snake River Plain began to form 17 million years ago after a meteor impact in what is now southeast Oregon. A weak spot in the crust and mantle formed and created a rhyolitic volcano. As the continental crust drifted to the south west the stationary hot spot, known as the Yellowstone Hotspot, it created new volcanoes. These volcanoes formed a wide swath of flat ground, eating through mountain ranges with violent eruptions. Today the hotspot lies under the geologically active Yellowstone area.

[Mike Darancette]

Though I'm still sad that any discovery of such a large impact site means "my" impact crater drops a spot in the world size ranking. ;)

There is no telling how big the Snake River collider would have been since the ensuing vulcanism would pretty much erase all traces of the crater. To cause impact volcanism a smaller high speed iron meteorite traveling at high speed and striking at a high angle could do the job nicely.

This impact theory is very controversial but there really isn't another explanation as to how a hot spot could have appeared out of nowhere.