History Stories

Ever since the mid-1800s, scientists have known that a major event occurred around 252 million years ago, at the end of the Permian period and the beginning of the Triassic. Fossil evidence had mounted by that time indicating that the boundary marked a major change in the diversity of life on Earth. Species such as trilobites (which left horseshoe crab-like tracks on the ocean floor) seemed to have completely disappeared by the Triassic period, along with massive coral reefs and entire forests of ferns and cyads.

Now, a team of Massachusetts Institute of Technology (MIT) researchers has used cutting-edge dating techniques on end-Permian rocks to make the most precise measurement yet of how long it took for the vast majority of Earth’s species to become extinct. According to the researchers’ findings, published recently in the Proceedings of the National Academy of Sciences, the entire mass extinction took place over around 60,000 years — more than 10 times faster than scientists had previously believed, and a virtual blink of an eye in geologic time.

Since 2006, MIT geologist Dr. Sam Bowring and his colleagues have been studying fossils found in the hills of Meishan, China, in an area made from rocks of the late Permian and early Triassic eras. To estimate the fossils’ age, they collected volcanic ash preserved in the rock around them, which contains radioactive atoms that have been in the process of breaking down since the ash was first ejected from a volcano. In 2011, Dr. Bowring’s team estimated the end-Permian extinction took less than about 200,000 years. Since that time, however, their dating technology has improved, allowing them to be more precise. They have narrowed the window down to less than about 60,000 years (with a margin of error of 48,000 years) and hope to narrow it even further in the future.

A more precise timetable for the end-Permian extinction is expected to help scientists evaluate different theories about what might have triggered it. Geologists have found evidence of massive volcanic eruptions in Siberia around the time of the extinction, as well as a spike in the ocean’s temperature of 18 degrees Fahrenheit. The eruptions, which helped formed the step-like hills of the Siberian Traps region, are thought to have covered more than 5 million cubic kilometers. As one theory goes, the Siberian volcanoes may have triggered the end-Permian extinction by releasing carbon dioxide and methane gases into the atmosphere and oceans, raising global temperatures and making life unsustainable for many species.

In addition to adjusting the timeframe of the extinction, Bowring and his colleagues confirmed that the oceans experienced a surge of light carbon around 10,000 years before the extinction, which likely reflected a similar surge of carbon dioxide into the world’s atmosphere. Now they are working to determine a similarly precise timeline for the Siberian Traps eruptions, in an effort to see where the two events–the eruptions and the mass extinction–may have overlapped. According to Seth Burgess, a graduate student at MIT and the lead author of the paper that reported the findings, “It is clear that whatever triggered extinction must have acted very quickly…fast enough to destabilize the biosphere before the majority of plant and animal life had time to adapt in an effort to survive.”

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