原文已被隐藏，你可用 快捷键 - 或点击 显示原文 按钮来查看原文
第1段
1 .This is Scientific American 60-Second Science. I'm Cynthia Graber. This'll just take a minute.
该句暂无译文！
2 .It was the largest of the five major mass extinctions in Earth's history, well before the dinosaur-killer 66 million years ago.
该句暂无译文！
3 .What's called the End Permian extinction, 252 million years ago, wiped out 96 percent of aquatic species and 70 percent of species on land.
该句暂无译文！
4 .Scientists have been trying to gauge the time frame of the extinction, in the hopes of determining its causes.
该句暂无译文！
5 .Now researchers say it's the fastest mass extinction known.
该句暂无译文！
6 .Using new tools and models, including a fresh analysis of rock formations in China, the researchers determined that the extinction took only about 60,000 years.
该句暂无译文！
7 .That's incredibly quick by geological standards, and is more than 10 times faster than previous estimates.
该句暂无译文！
8 .The report is in the Proceedings of the National Academy of Sciences.
该句暂无译文！
9 .Study author Samuel Bowring from MIT says they can't yet compare the speed of the previous extinction to the extinction rates caused by human activities today.
该句暂无译文！
10 .But, he says, their research is starting to help reveal how past environmental changes that influenced extinctions,
该句暂无译文！
11 .such as levels of carbon dioxide in the atmosphere, compare to the changes in those levels seen today.
该句暂无译文！
12 .In the midst of what many call the sixth extinction.
该句暂无译文！
13 .Thanks for the minute, for Scientific American 60-Second Science. I'm Cynthia Graber.
该句暂无译文！