WASHINGTON - During the world's biggest mass extinction, Earth seemed pretty close to a description of hell - fiery, smoky and explosive - created by massive volcanic eruptions, according to research dug up in China.

In geologic terms, it was surprisingly quick, and it may provide a scary lesson about climate change for our future, authors of the new study say. It was the third of five extinctions in world history, occurring even before dinosaurs roamed.

This extinction killed off more than three-quarters of life on the planet in an event scientists have called the Great Dying. The Chinese dig sites provide new dates and details of the event, which occurred 252 million years ago and may have lasted less than 100,000 years, far shorter than scientists had thought, according to the study published Thursday in the journal Science.

The study also bolsters the prevailing scientific concept that the giant die-off was caused by a massive shift in climate - global warming, prehistoric style - triggered by volcanic activity that is far beyond modern levels. The research also makes the case that the burst of carbon dioxide and methane thrown into the atmosphere that triggered the die-off took only about 20,000 years, less than previously thought, though the ecological damage lasted longer.

And devastating fires raged worldwide, not just where the volcanoes exploded, the paper said.

"Imagine drying out the Amazon and burning it up," said study co-author Douglas Erwin, a paleobiology curator at the Smithsonian Institution. "It certainly was a very uncomfortable time. You're killing off 75 to 90 percent of everything on the planet. It's not going to be terribly pleasant."

The air at times could be like the thick smog outside an old Eastern European power plant, Erwin said.

It was the only mass extinction in history to kill off hardy insects, Erwin said. Afterward, there were very few species left worldwide, and they had little diversity among different regions. It was only later that dinosaurs and mammals roamed the Earth.

The study is based on more than two dozen cross-sections of soil, both on land and under water, over thousands of miles in southern China.

But they should be representative of the entire world, given the shift of continents over the past 250 million years, said lead author Shu-zhong Shen of the Nanjing Institute of Geology and Paleontology. The study also offered the first evidence that the die-off in the sea and on land happened at the same time.