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Ancient megavolcanoes killed half the world's species

New rock dating techniques have helped narrow the timeframe of a chain of massive volcanic eruptions that wiped out half the world's species 200 million years ago, a study said Thursday.

The result is the most precise date yet -- 201,564,000 years ago -- for the event known as the End-Triassic Extinction, or the fourth mass extinction, said the study in the journal Science.

The eruptions "had to be a hell of an event," said co-author Dennis Kent, a paleomagnetism expert at Columbia University's Lamont-Doherty Earth Observatory.

They may offer a historic parallel to the human-caused climate change happening today, by showing how sharp increases in carbon dioxide can outpace vulnerable species' ability to adapt, researchers said.

The new analysis winnows the estimated date from its previous range of up to three million years to 20,000 years at most, a blink of an eye in geological terms.

The eruptions caused an already hot Earth to become even more stifling, killing off plants and animals and making way for the age of the dinosaurs -- before they, too, were obliterated some 65 million years ago, possibly by another volcanic event combined with a devastating meteorite strike.

Volcanoes roiled the Earth in a time when most of the land mass was united in one big continent, spewing some 2.5 million cubic miles of lava that, over time, split the terrain and led to the creation of the Atlantic Ocean.

For the study, scientists analyzed rock samples from Nova Scotia, Morocco and outside New York City, all of which came from this once-united landmass known as the Central Atlantic Magmatic Province.

An analysis of the decay of uranium isotopes in the basalt, a type of rock left by the eruptions, offered researchers more precise dates.

The eruption in Morocco was the earliest, followed by Nova Scotia about 3,000 years later and New Jersey 13,000 years later.

Sediments that lie below that time hold fossils from the Triassic era. Above that layer, they disappear, the study said.

Some of the lost creatures include eel-like fish called conodonts, early crocodiles and tree lizards.

"In some ways, the End Triassic Extinction is analogous to today," said lead author Terrence Blackburn, who carried out the study while at the Massachusetts Institute of Technology but is now with the Carnegie Institution.

"It may have operated on a similar time scale. Much insight on the possible future impact of doubling atmospheric carbon dioxide on global temperatures, ocean acidity and life on earth may be gained by studying the geologic record."

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