Nothing brings out creativity in the scientific community like a mass extinction. Sixty-five million years ago, dinosaurs suddenly vanished from the face of the planet. What caused it - widespread disease? destruction of the ozone layer? carbon monoxide poisoning? giant volcanoes? Maybe a space rock? A Verneshot? (supervolcano that causes an asteroid-like impact)??
How about this one: an asteroid hits the Yucatan Peninsula and sends a seismic shock wave deep into Earth's mantle. The rattling is so intense that a giant plume of magma awakens, rises to the surface, and bursts forth in a titanic display of volcanic activity in India's Deccan Plateau the likes of which the planet has rarely seen.
Now that's a theory.
It may not be as insane as it sounds. According to an article in New Scientist, several researchers take this idea very seriously, even suggesting that other mass extinctions may have been similarly triggered by a cosmic impact/supervolcano one-two punch.
Chief among them is Asish Basu of the University of Rochester, who published a paper in no less a journal than Science in 2003 in which he presented evidence of an impact in Antarctica 250 million years ago. That lines up nicely with the Alaska-sized lava deposits of the Siberian Traps, which are believed to be behind the Permian-Triassic extinction, the worst dying the planet has ever seen.