Volcanic climate change may have contributed to dinosaur extinction

ANN ARBOR, MICHIGAN — Massive volcanic eruptions in India may have contributed to the extinction of the dinosaurs, which has long been believed to be the result of a massive asteroid impact.

According to a timeline assembled by University of Texas at Austin researchers, the Chicxulub asteroid struck a shallow ocean some 66 million years ago, hitting it with the force of 10 billion atomic bombs. The blast set the land ablaze, igniting trees and plants up to thousands of miles away.

Although the asteroid caused destruction at the regional level when it hit, the impact itself was not what killed off the dinosaurs.

Instead, scientists say sulfur-bearing rocks were vaporized at the site, releasing an estimated 325 million metric tons of sulfur into the atmosphere, where it reflected sunlight away from the planet and caused global cooling.

Researchers believe the global climate change that followed was responsible for the mass extinction of the dinosaurs.

Global cooling disrupted photosynthesis, which killed the plants and caused the food chain to collapse.

Now, a new study published in Nature Communications has found evidence that another event may have contributed to the extinction.

The University of Michigan-led research collected and analyzed ancient fossilized shells from around the world, finding evidence of both ocean warming and high mercury concentrations when they were formed 66 million years ago.

These measurements are both symptoms of volcanic eruptions. They align with the onset of a series of violent eruptions that created India's Deccan Traps formations, starting before the extinction, and lasting on and off for about a million years.

Mercury is toxic to humans, fish, and wildlife. The levels researchers found in the ancient shells were found to be roughly equivalent to those in modern shells from mercury-polluted industrial sites.

Scientists believe that such a level of global mercury contamination indicates a volcanic climate change was already present before the extinction, and may have merely been accelerated by the impact event.