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.
Coincidence? Basu thinks not.
The same thing could be true for the dinosaurs. From the New Scientist piece:
"A big impact anywhere would have shaken the planet and created pressure that might have amplified deep-mantle volcanic activity already in progress," [Basu] says. If that was so, whether Shiva was an impact crater or not was irrelevant. An impact anywhere in the world could have been the trigger for the Deccan volcanism; arguably, it could even have been the well-documented Yucatán impact.
The "Shiva" mentioned above is one of the major loose ends of the theory. It's a giant basin filled with shattered rocks and weird, iridium-rich volcanic spires that some scientists think mark the site where an asteroid 40 kilometers (25 miles) in diameter hit Earth 65 million years ago. And right next door are the Deccan Traps deposits, which erupted at roughly the same time -- like their Siberian cousins, the massive volcanic formation could have caused a mass extinction.
That gives us two giant impacts and a supervolcano to reckon with. Did the Yucatan impact ripple through the planet and cause the Deccan eruptions? Was it Shiva, right next door? If all of those things happened at once, you'd expect the effects on life toe devastating. Sure, there was a pretty large extinction at the time, but it wasn't the worst the planet has seen. Not by a long shot.
Scientists will likely spend decades sorting out the particulars. But the idea of a cosmically-induced earthquake causing global pandemonium makes at least a little sense; the Chilean earthquake in February shortened Earth's day a fraction of a second and shifted the planet's pole, as did the magnitude 9.1 quake off Sumatra in 2004. A magnitude 9.5 earthquake in Chile in 1960, the largest ever recorded, triggered volcanic eruptions in the Andes. And none of those tremors hold a candle to the energy released from a large impact event.
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