Article posted Thursday, March 27, 2014 11:48am

About 252 million years ago, at the end of the Permian Period, 90 percent of all animal, plant and marine species on the planet suddenly disappeared. To find out why this catastrophe occurred, geochronologists studied the site of a huge, ancient volcano in Siberia. Using new methods to date basaltic rocks and fossil-containing rocks, they were able to calibrate over time the decay of radioisotopes in these rocks. This allowed them to evaluate atmospheric conditions shortly after the volcano erupted. Analysis of the temperature-sensitive oxygen isotopes revealed a staggering increase in global warming of 46-50 degrees F. The volcanic eruption threw tons of sulfur dioxide into the atmosphere, causing acid rain not unlike vinegar. The studies also showed that one or more of these massive volcanic eruptions dimmed sunlight and filled the atmosphere with carbon dioxide and sulfur dioxide—all of which killed off most life on the planet. It would take millions of years for life on the planet to recover. (Science, Dec. 20, 2013; science.nationalgeographic.com)