手機APP下載

您現在的位置: 首頁 > 英語聽力 > 雙語有聲讀物 > 萬物簡史 > 正文

萬物簡史(MP3+中英字幕) 第617期:冰河時代(14)

來源:可可英語 編輯:shaun ?  VIP免費外教試聽課 |  可可官方微信:ikekenet
 下載MP3到電腦  批量下載MP3和LRC到手機
加載中..

Before fifty million years ago, Earth had no regular ice ages, but when we did have them they tended to be colossal. A massive freezing occurred about 2.2 billion years ago, followed by a billion years or so of warmth. Then there was another ice age even larger than the first— so large that some scientists are now referring to the age in which it occurred as the Cryogenian, or super ice age. The condition is more popularly known as Snowball Earth.

在5000萬年前,地球上并沒有很有規律的冰川期,可是一當它們在地球上出現,其規模和持續時間都是十分驚人的。第一次大范圍的冰川期出現在大約22億年前,之后就是長達10億年左右的溫暖期。在這之后出現的冰川期比第一次來得更大——事實上,它是如此之大,以至于如今有些科學家提到那個時代時,都用上了覆冰紀或超級冰川期這樣的字眼。這種狀況更經常被稱為“雪球世界”。
"Snowball," however, barely captures the murderousness of conditions. The theory is that because of a fall in solar radiation of about 6 percent and a dropoff in the production (or retention) of greenhouse gases, Earth essentially lost its ability to hold on to its heat. It became a kind of all-over Antarctica. Temperatures plunged by as much as 80 degrees Fahrenheit. The entire surface of the planet may have frozen solid, with ocean ice up to half a mile thick at higher latitudes and tens of yards thick even in the tropics.
然而,“ 雪球”很難說明那一時期環境極其惡劣的程度。那種理論認為。由于陽光的照射量減少了約6%,產生(或保留)溫室氣體的能力降低,地球實際上堆以保持其熱量。地球變成了如同南極那樣的冰天雪地,氣溫降低了45攝氏度。整個地球表面都被凍得嚴嚴實實,高緯度地區的海洋結冰厚達800米,熱帶地區的也有幾十米厚。
There is a serious problem in all this in that the geological evidence indicates ice everywhere, including around the equator, while the biological evidence suggests just as firmly that there must have been open water somewhere. For one thing, cyanobacteria survived the experience, and they photosynthesize. For that they needed sunlight, but as you will know if you have ever tried to peer through it, ice quickly becomes opaque and after only a few yards would pass on no light at all. Two possibilities have been suggested. One is that a little ocean water did remain exposed (perhaps because of some kind of localized warming at a hot spot); the other is that maybe the ice formed in such a way that it remained translucent— a condition that does sometimes happen in nature.
這里存在一個嚴重問題:從地質學角度來看,整個地球,包括赤道地區在內,都被冰雪所覆蓋;可是從生物學角度來看,卻又確定無誤地表明在某些地方一定存在著未曾冰凍的水域。首先,藻青菌存活了下來,還進行了光合作用。進行光合作用需要陽光,可是要是你透過冰塊看,你會發現光線很快變得越來越暗,幾米之外就根本看不見光線了。對于這個問題,可能有兩種解釋:一是有一小部分水域確實未曾冰凍(也許是因為當地某個地方很熱);一是某些結構的冰塊是半透明的這種現輔時在大自然中確實存在。

If Earth did freeze over, then there is the very difficult question of how it ever got warm again. An icy planet should reflect so much heat that it would stay frozen forever. It appears that rescue may have come from our molten interior. Once again, we may be indebted to tectonics for allowing us to be here. The idea is that we were saved by volcanoes, which pushed through the buried surface, pumping out lots of heat and gases that melted the snows and re-formed the atmosphere. Interestingly, the end of this hyper-frigid episode is marked by the Cambrian outburst—the springtime event of life's history. In fact, it may not have been as tranquil as all that. As Earth warmed, it probably had the wildest weather it has ever experienced, with hurricanes powerful enough to raise waves to the heights of skyscrapers and rainfalls of indescribable intensity.

如果地球確實被冰凍過,那它又是怎樣重新變得溫暖起來的呢?這是一個很難于回答的問題。由于反射的熱量太多,一個處于冰凍狀態的星球會永遠保持這種狀態。挽救這種局面的力量似乎來自地球內部的巖漿。我們能在這里也許要再次感謝地殼的構造。我們認為,是火山救了我們。火山的噴發突破了冰川的封鎖,噴涌而出的熱量和氣體融化了地表的冰雪,使得大氣層重新得以改變。非常有意思的是,這一次高度寒冷的時期是以寒武紀大爆發——生命發展史上的春天——為結束的標志。當然,這樣一個春天并非總是風和日麗,因為隨著地球變暖。它經歷了有史以來最狂暴的天氣,強烈的颶風掀起摩天大樓高的巨浪,到處下著不可思議的瓢潑大雨。

重點單詞   查看全部解釋    
greenhouse ['gri:nhaus]

想一想再看

n. 溫室,暖房

 
intensity [in'tensiti]

想一想再看

n. 強烈,強度

 
radiation [.reidi'eiʃən]

想一想再看

n. 輻射,放射線

 
experienced [iks'piəriənst]

想一想再看

adj. 有經驗的

 
exposed [iks'pəuzd]

想一想再看

adj. 暴露的,無掩蔽的,暴露于風雨中的 v. 暴露,

 
planet ['plænit]

想一想再看

n. 行星

 
indebted [in'detid]

想一想再看

adj. 負債的,受惠的

聯想記憶
translucent [træns'lu:sənt]

想一想再看

adj. 半透明的

聯想記憶
evidence ['evidəns]

想一想再看

n. 根據,證據
v. 證實,證明

聯想記憶
melted [meltid]

想一想再看

adj. 融化的;溶解的 v. 融化;溶解(melt的過

 
?
發布評論我來說2句

    英語學習專題

    • 英語聽寫訓練
      聽寫強化訓練系統有聽寫比對,按句停頓,中文翻譯、聽寫錯詞提示等特色功能.
    • 經濟學人中英雙語版
      提供經濟學人中英雙語版文章、音頻、中英字幕,類別包括文藝、人物、科技、商業等..
    • 可可英語微信:ikekenet
      關注可可英語官方微信,每天將會向大家推送短小精悍的英語學習資料..

    可可英語官方微信(微信號:ikekenet)

    每天向大家推送短小精悍的英語學習資料.

    添加方式1.掃描上方可可官方微信二維碼。
    添加方式2.搜索微信號ikekenet添加即可。
    老时时开奖结果公布