The combination of two factors that led to the extinction of dinosaurs has been named

Repeated “volcanic winters” may have left dinosaurs hungry, cold and vulnerable to the deadly “final blow” of the asteroid that ultimately finished them off, reports the Daily Mail.

At least that’s the conclusion of an international team of researchers from Italy, Norway, Canada and the United States in a new study that analyzed sulfur and fluorine gases contained in ancient volcanic rocks of the infamous Deccan Traps supervolcano. Traps are a special type of continental magmatism, which is characterized by a huge volume of basalt outpouring in a geologically short time over large areas.

This sulfur and fluorine, released by the Deccan Plateau traps in what is now India more than 200,000 years before the extinction-level event, would have lowered global temperatures by as much as 10 degrees Celsius, according to a new study.

The findings bring further clarity to the raging debate between paleontologists and other scientists about what actually drove the dinosaurs to extinction. The new work is consistent with a compromise theory: the “momentum-driven extinction model.”

“Our study shows that climatic conditions were almost certainly unstable,” says study co-author and geologist Don Baker, “with repeated volcanic winters that may have lasted for decades before the extinction of the dinosaurs.”

“Our work helps explain this significant extinction event that led to the emergence of mammals and the evolution of our species,” says Baker, who teaches at Canada’s McGill University in Montreal.

The team analyzed trapped sulfur and fluorine compounds in samples taken from the Deccan Traps “lava pile” in India’s Western Ghats mountain range, near Bombay.

Minute concentrations of the compounds, measured in parts per million, were determined using synchrotron radiation X-ray fluorescence spectrometry, which bombards samples with magnetized corkscrews of radiation and then records how that radiation is reflected and scattered back.

Baker used a culinary analogy to explain the process of calculating the volume of atmospheric sulfur and fluoride from the small percentages contained in these lava rocks. “Imagine making pasta at home. You boil water, add salt, and then add the pasta,” Baker began in his statement. “Some of the salt in the water gets into the pasta,” he said, “but not that much.”

Baker and his team worked with similar known relationships to estimate how much of the gas compounds sulfur and fluorine entered the Earth’s atmosphere during the Cretaceous period.

A sustained decrease in temperature during the Late Cretaceous period, as estimated by past paleoclimate studies, was accompanied by an increase in the concentration of sulfur compounds in several layers of ancient lava from the Deccan traps: layers known as Thakurwadi, through the Boucher rock formations.

The sulfur content in these layers was found to be as high as 1,800 parts per million. According to the researchers’ calculations, this would indicate that a volume of sulfur dioxide gas measuring somewhere between 86,000 and 466,000 cubic kilometers erupted into the prehistoric atmosphere.

When it came to fluoride gases, Baker and his colleagues don’t believe it contributed to major climate change, but that its concentrations had other, more localized, toxic effects.

“There is historical evidence of localized effects of outgassing of fluoride,” they wrote in their study published in the journal Science Advances, “which readily precipitates from volcanic haze.”

These local impacts included “acid rain, crop failure and livestock poisoning” following the 1783 and 1784 eruptions of Iceland’s Laki volcano.

Essentially, the researchers suggest that the fluoride release from Laki Volcano may be a good example of how the supervolcanic activity of the Deccan Traps may have further harmed dinosaurs over 66 million years ago.

“Volcanism in the Deccan Traps set the stage for a global biotic crisis,” as the team put it in their new study, “by continually worsening environmental conditions, causing repeated short volcanic winters.”

But the “final blow,” they say, was almost certainly the well-known Chicxulub impact, when a carbon-rich asteroid crashed into Mexico’s Yucatan Peninsula some 66 million years ago.

The impact, which left a six-mile-wide crater visible to this day, devastated the planet, kicking up a hot cloud of dust, ash and steam and sending 25 trillion metric tons of material into the atmosphere, some of which even escaped Earth’s orbit.

Scientists say heating the rest of this material caused wildfires across 70 percent of the planet and left massive clouds of dust that hastened the onset of a new ice age.

But by then the dinosaurs were already suffering from bad weather, suggests the new paper by Baker and his team. “Our data set,” they wrote, “indicates that climate disruption caused by the volcano has already begun.”