World - Familiar Culprit May Have Caused Mysterious Mass Extinction
A planet heated by giant volcanic eruptions drove the earliest known wipeout of life on Earth.
It has long been our planet’s greatest and oldest murder mystery. Roughly 445 million years ago, around 85 percent of all marine species disappeared in a geologic flash known as the Late Ordovician mass extinction. But scientists have long debated this whodunit, in contrast to clearer explanations for Earth’s other mass extinctions.
“The Ordovician one has always been a little bit of an oddball,” said Stephen Grasby of the Geological Survey of Canada.
Now he and David Bond of the University of Hull in England say they have cracked the case in a study published last month in the journal Geology. Widespread volcanic eruptions unleashed enough carbon dioxide to heat up the planet and trigger two pulses of extinction separated by 1 million years, they report. If true, it places the first grand wipeout of life on Earth in good company: Many of the other major mass extinctions are also thought to be victims of global warming.
Scientists have offered a range of culprits — including toxic metals and radiation released from a distant galaxy — but the favored explanation has long been global cooling.