Evidence from ancient Antarctic seashells confirms that massive volcanic eruptions altered Earth’s climate, atmosphere and oceans just before dinosaur extinction 66 million years ago.

The eruptions from the Deccan Traps, a 200,000-square-mile volcanic province located in modern India spewed massive amounts of carbon dioxide (CO2) into the atmosphere. They have been suspected of contributing to dinosaur and ocean ecological malaise in the past. But the new study, using geochemical evidence of oceanic acidity and atmospheric CO2 for thousands of years prior to the meteorite-impact driven extinction, confirms the impacts of Deccan eruptions. The highly elevated concentration of CO2 acidified the oceans, directly affecting the organisms living there.

The shells, deposited during several thousands of years and up to the dinosaur-destroying impact, contain a chemical record of ocean conditions, including carbon content and acidity.

“The Earth was clearly under stress before the major dinosaur extinction event at 66 million years,” said Andrew D. Jacobson, a senior author of the paper. What’s more, other research on shells from around the globe suggests that the eruptions unleashed high levels of mercury into the atmosphere, soils, and sediments.

The amount of carbon in the atmosphere and oceans was increasing due to massive volcanic eruptions. Climate was changing and the oceans were much more acidic. That was bad news for dinosaurs, and especially marine life.

The researchers said that understanding how the Earth responded to past extreme warming and CO2 input can help us prepare for how the planet will respond to current, human-caused climate change.

“To some degree, we think that ancient ocean acidification events are good analogs for what’s happening now with anthropogenic CO2 emissions,” Jacobson said. “Perhaps we can use this work as a tool to better predict what might happen in the future. We can’t ignore the rock record. The Earth system is sensitive to large and rapid additions of CO2. Current emissions will have environmental consequences.”

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