WASHINGTON — The giant space rock that wiped out the dinosaurs may have set off a chain of cataclysmic volcanic eruptions on land and undersea, claims a new study that is already dividing scientists.

About 66 million years ago a 6-mile wide asteroid smacked into Earth, creating the Chicxulub crater in the Yucatan and sparking deadly chaos. Superhot particles rained from the air causing fires across the globe and sending temperatures higher. Then it got worse. Clouds of particles reflected the sun’s energy away, darkening the skies and cooling Earth at least 45 degrees for several years, scientists said. And that big hit set off earthquakes close to 100 times stronger than the biggest we’ve seen in modern times.

It was enough to kill off three-quarters of the life on Earth, especially most of the creatures and plants on land.

But there were even more reverberations, possibly deadly ones, the new study says.

New evidence suggests all that shaking triggered massive volcanic eruptions that spewed gases and particles into the air and water too. A study in Wednesday’s journal Science Advances figures sometime after the asteroid crash, unusual and extra strong eruptions happened on the floor of the oceans, probably in what are now the Pacific and Indian oceans. The study authors calculate that those ejected a tremendous amount of molten rock underwater – so much that on land it would cover the entire continental United States a couple hundred feet deep or so.

“We’re showing there was a lot more going on than we thought,” said University of Minnesota geophysicist Joseph Byrnes, the study’s lead author. “We’re painting a new sequence of events.”

These underwater volcanic areas – called mid-ocean ridges – often erupt, even today. But this happened on a far bigger scale.