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Extreme global warming caused devastating die-off

As much as 95 percent of the Earth's species disappeared 250 million years ago as a result of dramatic temperature changes likely influenced by fierce volcanic eruptions. 

By Charles ChoiLiveScience Contributor / October 18, 2012

Ammonoid mollusks showed a broad diversity one million years after the Permian extinction. The mass extinction that occurred at the end of the Permian period 252 million years ago was a body blow to marine organisms as the oceans became toxic.

Dr. A. Brayard and J. Thomas, University of Burgundy, Dijon, France via The New York Times

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Feverishly hot ocean surface waters potentially reaching more than 104 degrees Fahrenheit (40 degrees Celsius) may have helped cause the greatest mass extinction in Earth's history, researchers say.

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"We may have found the hottest time the world has ever had," researcher Paul Wignall, a geologist at the University of Leeds in England, told LiveScience.

The mass extinction at the end of the Permian Era about 250 million years ago was the greatest die-off in Earth's history. The cataclysm killed as much as 95 percent of the planet's species. One key factor behind this disaster was probably catastrophic volcanic activity in what is now Siberia that spewed out as much as 2.7 million square miles (7 million square kilometers) of lava, an area nearly as large as Australia. These eruptions might have released gases that damaged Earth's protective ozone layer.

After the end-Permian mass extinction came a time "called the 'dead zone,'" Wignall said. "It's this 5-million-year period where there's no recovery, where there is a very low diversity of life."

The dead zone apparently experienced a serious case of global warming, but the extremes this global warming reached were uncertain. To find out, scientists analyzed fossils dating from 253 million to 245 million years ago, shortly before and after the mass extinction. [Wipe Out: History's Most Mysterious Extinctions]

Unraveling an isotope mystery

The researchers focused on isotopes or atomic variants of oxygen within these fossils. All isotopes of oxygen have eight protons in their atomic nuclei, but differ in the number of neutrons they possess — oxygen-16 has eight neutrons, while oxygen-18 has 10.

As marine creatures form shells, bones and teeth, "they tend to use lighter isotopes of oxygen under warmer conditions," Wignall said. "You can still see this today when looking at modern-day sea creatures. The ratios of oxygen isotopes in their shells are entirely controlled by temperature."

The researchers analyzed strange eel-like creatures known as conodonts, which are known mainly by their elaborate mouthparts. The fossils came from the Nanpanjiang Basin in south China, helping reconstruct what temperatures were like around the equator at the end-Permian.

Different groups of conodonts shed light on what temperatures were at different depths. For instance, one group, Neospathodus, lived down about 230 feet (70 meters) deep, while others, such as PachycladinaParachirognathus andPlatyvillosus lived near the surface.

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