An incredible outpouring of lava 66 million years ago could have set off environmental changes that killed off the dinosaurs, a new study finds.
The research reports precise dates for India's Deccan Traps, mountain-high piles of basalt lava flows that cover as much territory as France. The youngest lava flows emerged 66.29 million years ago, about 250,000 years before the Chicxulub space rock crashed into eastern Mexico's Yucatan Peninsula. The findings could revive the idea that the Deccan Traps caused the Cretaceous-Paleogene extinction — a hypothesis long pushed aside in favor of the asteroid impact.
"Now we can say when the Deccan Traps started," said lead study author Blair Schoene, a geologist at Princeton University in New Jersey. "For me, it's not whether the impact or the Deccan traps caused the extinction. The point is that without a precise timeline, you can't understand what happened." [Wipe Out: History's Most Mysterious Extinctions]
The study was published Thursday (Dec. 11) in Science Express, the online edition of the journal Science.
The dinosaurs and 75 percent of other Cretaceous species suddenly vanished after the giant asteroid slammed into the Yucatan 66.04 million years ago. The big extinction and the Chicxulub impact are separated by about 30,000 years, an instant in geologic time, according to a 2013 study. The prevailing view credits the impact for the massive die-off.
But animals and plants had already started disappearing from the fossil record before the asteroid impact, at the same time the Deccan Traps eruptions began. The Deccan Traps derive their name from the Dutch word for stairs (trap). The steplike basalt lava flows stack up nearly 9,800 feet (about 3,000 meters) high. Proponents of the volcanic extinction model argue that climate-altering volcanic gases made Earth inhospitable for many species by changing temperatures and ocean acid levels.
However, until now, no one could closely tie the volcanic activity to the Cretaceous extinctions. "The Deccan Traps had never really been well dated," said Paul Renne, director of the Berkeley Geochronology Center in California, who was not involved in the study.