英语听力文摘 English Digest 576、希腊不总是人间天堂！

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　　Fira is a typical Greek city overlooking the Aegean Sea. Sitting atop a twelve hundred foot cliff on Santorini Island, it’s an ideal vacation spot. But this island wasn’t always a paradise. Thirty five hundred years ago, it was the site of one of the largest volcanic eruptions³ in historic times.

 

　　The Santorini volcano blew up with very little warning, causing a massive tsunami⁴ that destroyed coastal⁵ towns around the Mediterranean⁶. The volcano collapsed⁷ to form what looks like a collection of small islands, but the islands are actually part of the rim⁸ of its four mile wide sunken caldera.

 

　　The volcano’s long slumber⁹, followed by such a sudden and massive eruption², was a puzzle to scientists. Why does a volcano sit dormant¹⁰ for thousands of years and then suddenly erupt? Scientists think they have found a clue in layers of crystal rock.

 

　　Magnesium¹¹ is one element present in the volcano’s different rock layers. Since it diffuses¹² slowly through crystalline rock, scientists can calculate rock ages by how much magnesium is present.

 

　　Scientists found that almost all of the crystal layers on Santorini were deposited just before the eruption. That meant that several cubic miles of hot magna rose from the depths of the volcano very rapidly. The magma melted and mixed with the rocks just below the surface immediately before the massive explosion. The volcano that had been sleeping for thousands of years woke in the blink of an eye.

 

　　Researchers don’t know what caused such a large volume of magma to rise so quickly, but their findings may give scientists a clue to help predict the next big eruption. GPS measurements show that the rim of Santorini is deforming¹³ right now, indicating that more magma may be on the rise.

 

　　希腊岛屿显示火山活动迹象

 

　　菲拉是一座典型的希腊城市，坐落在圣托里尼岛1200英寸高的悬崖之上，俯瞰爱琴海，是一处理想的度假胜地。但这座岛屿在过去并非一直是人间天堂。3500年前，这里发生了历史上最大规模之一的火上喷发。

 

　　圣托里尼火山在爆发之前几乎没有任何征兆，爆发后引起一场巨大的海啸，摧毁了地中海沿岸的城镇。接着火山发生塌陷，形成了如今这一系列小岛。这些岛屿事实上是沉入海水中的四英里宽火山口的一部分。

 

　　圣托里尼火山在长期沉寂后突然发生大规模的爆发，这一现象令科学家们感到费解。为何一座火山几千年来一直处于休眠状态，却会突然爆发呢？科学家们认为他们已在结晶岩层中找到了线索。

 

　　镁元素存在于火山的不同岩层中。由于它在结晶岩层中扩散缓慢，因此科学家们可以通过检测镁元素含量来计算岩层的年龄。

 

　　科学家们发现，圣托里尼岛上几乎所有的结晶岩层均恰好在火山爆发之前沉积下来。这意味着，体积达数立方英里的火热岩浆从火山深处迅速喷发出，在大规模火山爆发之前立即将地表下的岩石融化，并与之混合。已沉睡千年的火山就这样在眨眼之间苏醒了。

 

　　研究人员不清楚是什么原因导致如此多岩浆的快速喷发，但他们的研究发现也许可以为科学家们预测下一次的大爆发提供线索。GPS测量显示，圣托里尼火山口边缘正在变形，这预示着更多的岩浆可能正蓄势待发。

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