万物简史 第323期:美丽而危险(6)

 　　The ash fall from the last Yellowstone eruption¹ covered all or parts of nineteen western states (plus parts of Canada and Mexico), 上一次黄石火山爆发所喷出的火山灰，铺满了西部19个州的全部地区或部分地区（加上加拿大和墨西哥的部分地区），

　　nearly the whole of the United States west of the Mississippi. 几乎涵盖了美国密西西比河以西的整个地区。

　　This, bear in mind, is the breadbasket of America, an area that produces roughly half the world's cereals. 记住，这里是美国的粮仓，生产世界上差不多一半的谷物。

　　And ash, it is worth remembering, is not like a big snowfall that will melt in the spring. 还不要忘记，火山灰不像一场大雪那样一到春天就会融化。

　　If you wanted to grow crops again, you would have to find some place to put all the ash. 要想再种庄稼，你不得不找个地方堆放所有的火山灰。

　　It took thousands of workers eight months to clear 1.8 billion tons of debris² from the sixteen acres of the World Trade Center site in New York. 几千名工人花了8个月的时间才从纽约世贸中心6.5公顷的废墟上清理掉18万吨垃圾。

　　Imagine what it would take to clear Kansas. 想一想，清理堪萨斯州要花多少时间。

　　And that's not even to consider the climatic consequences. 我们还没有考虑对气候产生的影响。

　　The last supervolcano eruption on Earth was at Toba, in northern Sumatra, seventy-four thousand years ago. 世界上上一次超级火山爆发发生在苏门答腊北部的多巴，那是在74000年以前。

　　No one knows quite how big it was other than that it was a whopper. 谁也不知道它的强度有多大，但肯定大得吓人。

　　Greenland ice cores show that the Toba blast was followed by at least six years of "volcanic³ winter" 格陵兰的冰核显示，多巴火山爆发以后，至少有长达6年的“火山冬天”，

　　and goodness knows how many poor growing seasons after that. 天知道之后又有多少个糟糕的生长期。

　　The event, it is thought, may have carried humans right to the brink⁴ of extinction⁵, 据认为，那次爆发几乎将人类灭绝，

　　reducing the global population to no more than a few thousand individuals. 使全球的人口减少到不足几千人。

　　That means that all modern humans arose from a very small population base, which would explain our lack of genetic⁶ diversity. 这意味着，那几千人是所有现代人的共同祖先，这也说明了我们为什么缺少基因的多样性。

　　At all events, there is some evidence to suggest that for the next twenty thousand years 无论如何，有证据表明，在此后的两万年里，

　　the total number of people on Earth was never more than a few thousand at any time. 地球上的总人数从没有超过几千。

　　That is, needless to say, a long time to recover from a single volcanic blast. 不用说，从一次火山爆发中恢复过来要花很长的时间。

1 eruption   

n.火山爆发；（战争等）爆发；（疾病等）发作

参考例句：

• The temple was destroyed in the violent eruption of 1470 BC.庙宇在公元前1470年猛烈的火山爆发中摧毁了。
• The eruption of a volcano is spontaneous.火山的爆发是自发的。

2 debris   

n.瓦砾堆，废墟，碎片

参考例句：

• After the bombing there was a lot of debris everywhere.轰炸之后到处瓦砾成堆。
• Bacteria sticks to food debris in the teeth,causing decay.细菌附着在牙缝中的食物残渣上，导致蛀牙。

3 volcanic   

adj.火山的；象火山的；由火山引起的

参考例句：

• There have been several volcanic eruptions this year.今年火山爆发了好几次。
• Volcanic activity has created thermal springs and boiling mud pools.火山活动产生了温泉和沸腾的泥浆池。

4 brink   

n.(悬崖、河流等的)边缘，边沿

参考例句：

• The tree grew on the brink of the cliff.那棵树生长在峭壁的边缘。
• The two countries were poised on the brink of war.这两个国家处于交战的边缘。

5 extinction   

n.熄灭，消亡，消灭，灭绝，绝种

参考例句：

• The plant is now in danger of extinction.这种植物现在有绝种的危险。
• The island's way of life is doomed to extinction.这个岛上的生活方式注定要消失。

6 genetic   

adj.遗传的，遗传学的

参考例句：

• It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
• Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。