Dinosaurs Were Killed By Asteroid Impact and Volcanism, New Study Shows

The argument about what killed dinosaurs may finally be settled. Researchers from the University of California Berkeley say a one-two punch consisting of an asteroid impact that occurred 66 million years ago and a resulting series of volcanic eruptions in India ultimately wiped out dinosaurs and many other land and marine animals.

"Based on our dating of lavas, we can be pretty certain that the volcanism and the impact occurred within 50,000 years of the extinction, so it becomes somewhat artificial to distinguish between them as killing mechanisms: both phenomena were clearly at work at the same time," Paul Renne, lead researcher and a professor from the University of California Berkeley, said in a news release. "It is going to be basically impossible to ascribe actual atmospheric effects to one or the other. They both happened at the same time."

Researchers also concluded that the Deccan Traps lava flows, which at the time were erupting at a slower pace, doubled in output within 50,000 years of the asteroid or comet. The amounts of toxic dust and fumes emitted into the atmosphere during these events would have drastically changed Earth's climate killed many species.

So how did the asteroid trigger increased volcanism? Researchers believe that the impact abruptly changed the volcanoes' plumbing systems, drastically altering volcano chemistry and frequency of eruptions. With more frequent, long-term eruptions, species were unable to recover for 500,000 years following this impact. This time period is also known as the KT boundary.

"The biodiversity and chemical signature of the ocean took about half a million years to really recover after the KT boundary, which is about how long the accelerated volcanism lasted," Renne added. "We are proposing that the volcanism unleashed and accelerated right at the KT boundary suppressed the recovery until the volcanoes waned."

These findings, recently published in the journal Science, shed light on what caused the mass extinction.  

"If our high-precision dates continue to pin these three events -- the impact, the extinction and the major pulse of volcanism -- closer and closer together, people are going to have to accept the likelihood of a connection among them," Mark Richards, co-author of the study and a UC Berkeley professor, said in a statement. "The scenario we are suggesting -- that the impact triggered the volcanism -- does in fact reconcile what had previously appeared to be an unimaginable coincidence." 

This new evidence provides the most accurate dates for the volcanic eruptions before and after the impact, and helps settle the long-debated question regarding what role these two global events played in the last mass extinction. 

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