字神帝國英語天地

 
 今日主題：Heat ID'd as Subtle Cause of Rockfalls  溫度上升岩石下落

 洪欣老師推薦：托福聽力最好的課外教材：60-Second Science
 康康精選托福會考的主題，堅持每天精聽一定會進步的哦!!

 建議方法：
1. 先聽兩三遍 (不看文稿)
2. 再一句一句聽寫 (每句都要聽寫數遍，直到寫出85%以上的字)
3. 最後check文稿，看哪聽不出來，單字沒背過，還是發音不熟。
4. 堅持天天聽，就能每天進步哦。

 MP3音檔 (按右鍵可下載聽)：喜歡的同學，幫忙推或按讚哦~~
http://online1.tingclass.net/voas…/2016/20160504sa_earth.mp3

 只有音檔怎夠，聽不懂地方，不用怕，康康幫你準備好中英文稿了：

 中英文稿：
The floor of Yosemite Valley is littered with piles of rocks that crumbled off the park’s iconic cliffs. These rockfalls happen all the time, becauseYosemite’s granite walls are riddled with cracks produced by geologic stress. Scientists know the rockfalls can be triggered by things like earthquakes, rainfall, and freezing and thawing ice. But many falls occur without an obvious cause. Now researchers think that heat may be the culprit.
Yosemite Valley山谷的地面散落著成堆的從公園內特有的懸崖峭壁上崩裂下的岩石。這些散落岩石之事時有發生，因為Yosemite山谷上的花崗岩峭壁因為地質 上的壓力造成了許多斷裂的空洞。科學家們知道這些岩石散落的原因可以是地震，暴雨以及凍融的冰河。但是，多數情況下岩石墜落的毫無徵兆。現在研究人員認為 熱能也許是罪魁禍首。

“We noticed that there had been a bunch of rockfalls that were happening in the summertime, on particularly hot days.” Brian Collins, a research civil engineer with the U.S. Geological Survey. “And we noticed when we looked at the timing that they were happening in the afternoon, when we thought the temperatures were at their hottest.”
我們已注意到，當在夏季的時候，會有許多的岩石墜落，特別是很熱的那幾天。這是Brian Collins，美參與國地理調查的城市工程研究人員。我們還注意到，發生岩石墜落的事件往往是下午，我們過去認為此時是一天中最熱的一段時間。

Collins and Greg Stock, Yosemite’s park geologist, wanted to know if small rock movements, induced by changing temperatures, might weaken cracks and contribute to rock falls. So the researchers—who are both climbers—found a suitable fracture near the base of a 500-meter-tall cliff and installed instruments called crack meters, which monitored the width of the crack over time.
Collins 和 Greg Stock, Yosemite公園中的地理學家，他們希望知道是否由於溫度的變化引發的小型岩石移動事件，會使山體的裂縫變得脆弱，從而最後導致岩石墜落。所以這些研 究人員們——他們還都是登山愛好者——在接近500米高的山崖底部發現了的 一塊小片地區，並且安裝了被稱為裂縫儀的設備，用於檢測不同時間下岩石裂縫的寬度。

The devices revealed that the crack grew almost a centimeter wider during the warmest part of the day. It shrank again when temperatures cooled off, for instance, at night and during the winter. But overall, the scientists found that the average width of the fracture grew over the course of a summer and over the entire three and a half-year study period, bringing the crack closer to breaking.
應用這些設備顯示出，裂縫在一天中最溫暖的時段裡幾乎被拓寬了一釐米。當溫度再次變低後它又收縮回去了，比如，在晚間和冬季時段。但是，總體上講，科學家 們發現斷裂處的平均寬度是在整個夏季是增加的，並且在他們整個3.5年的研究期間也是增加的，這些都造成了裂縫增加岩石趨於斷裂。

“We think that what happened was that every cycle — as the rock goes back and forth and back and forth — you’re getting to a part that we call subcritical crack growth. And that means that the crack where the rock is attached to the cliff is actually fracturing at a microscopic level. And so if you do that over the course of a year, then eventually you’re going to do some permanent damage to those points of attachment.” The study is in the journal Nature Geoscience.
我們認為發生了迴圈——隨著岩石來來回回滾動——你正處一個我們稱之為臨界裂縫增長的階段。這就意味著，岩石連接著山崖的裂縫部分實際上正在以微小的幅度 斷裂著。所以，如果你在一年中的這個階段這麼做，那麼最後，你就在對那些連接點進行永久性的破壞。該研究結果已經發表在《自然地理科學》雜誌上。

The slab of rock the scientists studied hasn’t fallen yet, and Collins doesn’t know how many cycles it will take before this or any other fracture finally breaks. When it does, the trigger might be a particularly sweltering day, when the partially detached slab is farthest away from the cliff. Or it could be another process, helped along by the fact that temperature changes already weakened the crack.
科學家們研究的岩石板還沒有墜落，而Collins也不知道在這個或者其它最後要斷裂的部分會在多少個上述微小的迴圈刺激之下才會最終斷裂。一定在是某個 特別悶熱的日子，當特別的一塊岩石板從山崖上飛速脫離時，岩石就發生斷裂了。或者，由於另外的事件，由於溫度變化説明了已經很脆弱的岩石裂縫，造成最後的 斷裂。

Either way, the results will help researchers assess the rockfall hazard in steep, rugged terrain. Because now they know when the mercury goes up, rocks are more likely to come down.
無論哪種方法，結果都將有助於研究人員們評估陡峭崎嶇的岩層地帶岩石墜落的災害風險。因為現在，他們已經知道當水銀柱越上升，岩石就越容易墜落。