The NASA finding gives little comfort to those who still believe that volcanism alone did in the dinosaurs. But they are encouraged by a novel "double-whammy" theory suggesting that an impact on one side of the earth could produce massive volcanic activity at the antipode -- a point directly opposite on the far side -- and that the combined effect would cause disaster. Says Jon Hagstrum, the U.S. Geological Survey paleomagneticist who co-authored the theory: "This would be the best way to trigger worldwide mass extinctions because you have both hemispheres affected."
