西伯利亞發現神秘環形山

　　7月22日CNN聽力：西伯利亞發明許多秘密環形山

　　Time for the Shoutout.

　　Which of these places is largest?

　　If you think you know it,shout it out.

　　Is it Siberia,Sahara Desert,Amazon Rainforest orAustralia?

　　You've got three seconds.Go.

　　The total area of Siberia is 5.2 million squaremiles,making it,by far,the largest region on this list.

　　That's your answer and that's your Shoutout.

　　All right,put another way,if you can find Northern Asia on a map,you've found Siberia.

　　It makes up almost 10 percent of the world's land surface.

　　But fewer than 40 million people live there.

　　That's smaller than the population of Argentina.

　　And Siberia's ferocious winters help explain that.

　　One thing that can't be explained yet is a natural phenomenon appearing in parts of Siberia.

　　A mystery at the end of the Earth.

　　giant gaping holes in the ground appearing out of nowhere.

　　It's happening in one of the most remote spots on the planet,in far Northern Russia,Siberia'sYamal Peninsula.

　　Translated,that's literally the end of the world.

　　The first crater appeared last summer.

　　Then came several more. Scientists were baffled.

　　I've never seen such craters anywhere in Yamal where I've been,and I've never heard mycolleagues talk of anything similar.

　　Now they count at least seven large craters,some of them up to 100 meters across.

　　Two have turned into lakes and one is just a few kilometers away from a major Gazprom naturalgas field.

　　Professor Vasily Bogoyavlensky and a team of experts have made several expeditions toSiberia,taking samples,gathering evidence,even braving sub-zero cold to climb down inside oneof the deepest craters for a closer look.

　　He suspects there are dozens more in the region and says they pose a serious threat.

　　Yes,it's very serious.

　　And if such craters will take place in the industrial region,it could be a quite serious disaster.

　　So what's behind them?

　　Early speculation ran wild,from meteorites and stray missiles to even UFOs and aliens.

　　Bogoyavlensky believes a more plausible theory is that the release of methane gas is sparkingunderground explosions,leaving behind the massive craters.

　　But that still does not solve the mystery.

　　We don't know exactly from where this gas came.

　　Some experts say global warming may be causing Siberia's ice to melt,releasing the dangerousmethane blasts.

　　While scientists continue to debate and investigate,for now,the mystery only deepens.

　　Linda Kinkade,CNN.

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