A massive asteroid strike 66 million years ago triggered a string of potent volcanic eruptions that spelled doom for the dinosaurs, US researchers said Thursday.

Just what led to the demise of the dinosaurs is often debated among scientists, and the latest findings in the journal Science suggest that both events are to blame, not one or the other.

Scientists studied the Deccan Traps lava flows in India, and their most accurate dating yet shows that the volcanoes doubled their output in close proximity to the asteroid or comet strike that set off the last mass extinction on Earth.

"Based on our dating of the 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," said lead researcher Paul Renne, a University of California, Berkeley professor of earth and planetary science.

"It is going to be basically impossible to ascribe actual atmospheric effects to one or the other. They both happened at the same time."

Together, the asteroid impact and the volcanic eruptions would have "blanketed the planet with dust and noxious fumes, drastically changing the climate and sending many species to an early grave," said a statement from UC Berkeley.

The impact of the asteroid changed the underground plumbing in the volcanoes, making some magma chambers larger so they spouted more lava when they erupted.

It would take Earth and its land and ocean life about 500,000 years to emerge from the devastation.

"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," said co-author Mark Richards, also a UC Berkeley professor of earth and planetary science.

"The scenario we are suggesting -- that the impact triggered the volcanism -- does in fact reconcile what had previously appeared to be an unimaginable coincidence."