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New evidence for volcanoes as source of mass extinction

volcano mass extinctionPaleontologists have found more solid evidence that volcanoes likely set off the Guadalupian mass extinction in the Middle Permian about 260 million years ago.

Previous studies have pointed to volcanoes as likely instigators of large-scale extinctions, such as the Siberian Traps that might have kicked off the subsequent Permian-Triassic extinction (in which as many as 70 percent of Earth's species disappeared). But, note the authors of the new study, published online today in Science, the link between volcanism and extinctions has been difficult to confirm.

A site in the Emeishan province in southwest China has turned up a telling layer of volcanic rock between sedimentary layers of old shallow seabed, reports the paper. An analysis of fossils in the sedimentary rock directly above (i.e. after) the volcanic layer shows a sharp change in the number and types of marine life, namely algae and foraminifers.

"The abrupt extinction of marine life we can clearly see in the fossil record firmly links giant volcanic eruptions with global environmental catastrophe," Paul Wignall, a professor of paleontology at the University of Leeds and lead author on the study, said in a statement.

How could a large volcanic event change the environment so drastically? A surge of molten lava (more than 310,000 cubic miles—or 500,000 cubic kilometers) pushing into a shallow sea would create an explosion like a massive version of "throwing water into a chip [French fry] pan," Wignall explained. The explosion would have thrown large amounts of sulfur dioxide into the stratosphere, causing cloud formation, cooling and acid rain, spelling death to many of the sea's creatures.

During the Permian Period (299 to 251 million years ago) at the tail end of the Paleozoic era, most of Earth's land was still united in Pangaea, and amphibians and archosaurs (proto-dinosaurs) roamed the land while cephalopods and foraminifers populated the waters.

Image of basalt from the flow shows how bubbly and gas-rich the eruptions were, courtesy of Science/AAAS

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