New research suggests that dinosaurs were hit with a double whammy -- a giant meteor striking Earth and volcanic eruptions -- causing them to go extinct.
The Age of Dinosaurs ended roughly 65 million years ago with the K-T or Cretaceous-Tertiary extinction event, which killed off all dinosaurs except those that became birds, as well as roughly half of all species on the planet. The prime suspect is an asteroid or comet impact, which left a vast crater at Chicxulub on the coast of Mexico.
Another leading culprit is a series of colossal volcanic eruptions that occurred between 63 million to 67 million years ago. These created the gigantic Deccan Traps lava beds in India, whose original extent may have covered as much as 580,000 square miles (1.5 million square kilometers), or more than twice the area of Texas.
Arguments over which disaster killed the dinosaurs often revolve around when each happened and whether extinctions followed. Previous work had only narrowed the timing of the Deccan eruptions to within 300,000 to 500,000 years of the extinction event.
Now research suggests the mass extinction happened at or just after the biggest phase of the Deccan eruptions, which spewed 80 percent of the lava found at the Deccan Traps.
"It's the first time we can directly link the main phase of the Deccan Traps to the mass extinction," said Princeton University paleontologist Gerta Keller.
Keller and colleagues focused on marine fossils excavated at quarries at Rajahmundry, India, near the Bay of Bengal, about 600 miles (1,000 kilometers) southeast of the center of the Deccan Traps near Mumbai. Specifically, they looked at the remains of microscopic shell-forming organisms known as foraminifera.
The researchers found these simple foraminifera seem to have popped up right after the main phase of the Deccan volcanism. This in turn hints these eruptions came immediately before the mass extinction, and might have caused it.