[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.

[casino66]

Obviously, to some, it was Bush's fault.

[Heatseeker]

Sounds OK to me - to answer my own question, at least in part, I found this New Scientist article from 2002 discussing the link between impact events and volcanism.