The asteroid that crashed into the Earth 66 million years ago may not have been the sole cause of the end of the dinosaurs; it may in fact have set off a "double whammy" in which the impact triggered massive volcanic eruptions that finished the job, researchers suggest.
The asteroid that crashed into the Gulf of Mexico would have "rung" the Earth like a bell, geologists say, and could have triggered eruptions including massive lava flows in India that covered an area the size of California with lava up to a mile deep, they say.
Those eruptions in what are known as the Deccan Traps in what is now India, lasted for hundreds of thousands of years and likely emitted huge amounts of climate-altering gases like carbon dioxide into the atmosphere, possibly finishing off what the asteroid started in terms of the fate of the dinosaurs, a study published in The Geological Society of America Bulletin suggests.
"If you try to explain why the largest impact we know of in the last billion years happened within 100,000 years of these massive lava flows at Deccan ... the chances of that occurring at random are minuscule," says study team leader Mark Richards, a professor of earth and planetary science at the University of California, Berkeley. "It's not a very credible coincidence."
The Deccan lava eruptions had in fact begun before the asteroid impact, but may have been "re-ignited" about 100,000 years later and amplified by the effects of the cosmic collision, the researchers say.
Richards has proposed that plumes of hot rocks rise through the mantle of the Earth every 20 million to 30 million years to generate huge flows of lava called flood basalts, similar to what is seen in the Deccan Traps.
The last four of the six known mass extinctions of life on Earth have been associated with the timing of these massive eruptions, he says.
The asteroid that created the Chicxulub crater off the Yucatán Peninsula in the Gulf of Mexico may have generated magnitude 9 earthquakes anywhere on the Earth, sufficient to re-ignite the Deccan flood basalts, he adds.
"This was an existing massive volcanic system that had been there probably several million years, and the impact gave this thing a shake and it mobilized a huge amount of magma over a short amount of time," Richards suggests.
The 100,000-year time gap between the impact and the resumed volcanic activity makes sense, he says; it would take just about that amount of time for the massive amounts of magma to reach the Earth's surface.
