The extinction of the dinosaurs some 66 million years ago was triggered by massive volcanic eruptions in India, and cemented by the arrival of the Chicxulub meteorite in Mexico.

The two events occurred within a few hundred thousand years of one another, making it difficult to tell which drove three-quarters of life on Earth — including the dinosaurs — to extinction. Sierra Petersen at the University of Michigan in Ann Arbor and her co-workers studied a fossil record of mollusc shells from Seymour Island in Antarctica, and used isotope analysis to estimate past temperature change. An 8 °C spike marking the onset of the Deccan Traps volcanic eruptions is followed by a smaller spike some 150,000 years later, coinciding with the Chicxulub impact.

The scientists conclude that the meteorite delivered the final blow to ecosystems already weakened by the eruptions.

Nature Commun. 7, 12079 (2016)