A long-simmering debate over what killed the dinosaurs is heating up anew as a team of UC Berkeley scientists suggests that an asteroid slamming into Earth must have triggered the eruptions of thousands of volcanoes on the other side of the planet — a combined event that could have helped to doom the beasts.

Led by UC Berkeley geologist Mark Richards, the group proposed that when the giant asteroid hit Earth about 66 million years ago, its impact sent such violent tremors through the planet’s crust that it set off a wave of volcanic eruptions half a world away.

Those eruptions, known as flood basalts, “were among the largest in the history of the planet, and would have buried all of California a mile deep in lava,” Richards said.

But the asteroid’s impact itself, which gouged an immense crater in the ocean floor off Mexico’s Yucatan Peninsula, remains the “main cause” of the event that drove most of the world’s dinosaurs and three-quarters of all other life on Earth to extinction, Richards said.

Both events could have raised such immense plumes of toxic gases that they would have darkened Earth, lowered global temperatures, and made it impossible for most life to exist. The result was one of the world’s frequent mass extinctions.

A report by Richards and his colleagues was published online Friday in the Geological Society of America Bulletin.

But the report wasn’t quite enough for Gerta Keller, a Stanford-trained geologist at Princeton University, who, in one of the longest-running scientific debates on record, has been a leading proponent of the theory that the volcanic eruptions in what is known as India’s Deccan Traps caused the mass extinction.

“Obviously I’m delighted that the Berkeley team is finally accepting Deccan volcanism as critical in causing the mass extinction,” she said in an e-mail after reading the report from Berkeley. “It is a step in the right direction.”

Much of the geologists’ information, she said, is circumstantial, highly speculative and outdated.

Keller has long maintained that the great asteroid impact had nothing to do with the dinosaurs’ mass extinction and that only the eruptions in the Deccan Traps could have raised the toxic clouds that killed them and so much of life on Earth. She has

But in an interview Friday Richards said he believes the thrust of his team’s report should persuade Keller that the disagreements between the two groups are narrow, and that indeed it is possible that the Deccan Traps eruptions played a significant role in the mass extinction of 66 million years ago.

To Richards and his colleagues, though, the timing of all these events — the asteroid, the volcanic eruptions and the mass extinctions — is crucial.

Paul Renne, a geologist on Richards’ team and an expert on dating objects in the Earth’s crust, dated the impact of the giant asteroid near Mexico’s Yucatan Peninsula more precisely than ever, calculating that it gouged out a huge crater, called Chicxulub, at some point between 65.5 million and 66.3 million years ago — or approximately 66.04 million years ago.

Those dates span a time known as the K-T Boundary, the time between the Cretaceous and Tertiary periods, when three-quarters of all life on Earth, including the dinosaurs, vanished.

The theory that the asteroid impact caused that mass extinction was instantly controversial when it was first advanced by the noted Berkeley geologist Walter Alvarez and his father, the late physicist Luis Alvarez, 25 years ago.

Walter Alvarez and Renne, along with scientists in Italy, England and the Netherlands, co-authored Richards’ report.