火山爆发凶，炎夏一扫空:火山爆发

　　炎炎夏日，一见到太阳就头疼――夏天为什么就这么热呢？如果每当遇到高温的日子地球能自动调节，稍微降低气温就好啦！现在，科学家们发现火山爆发竟然能降低全球气温哦――凉爽的夏天，这是多么美好的愿望啊……可是其中的利弊如何？跟着小编一起研研究究吧。
　　
　　The biggest volcanic 1)eruption ever recorded in human history took place nearly 200 years ago on Sumbawa, an island in the middle of the Indonesian 2)archipelago.
　　The volcano is called Tambora, and according to University of Rhode Island volcanologist Haraldur Sigurdsson, the eruption is one of the most overlooked in recorded history.
　　Tambora’s explosion was 10 times bigger than Krakatoa and more than 100 times bigger than Vesuvius or Mount St. Helens. Approximately 100,000 died in its shadow.
　　“The eruption went up about 43 kilometers into the atmosphere. That is about 30 miles � much higher than any airplane flying today � and 3)emitting a volume that is about 100 cubic kilometers of 4)molten rock in the form of ash and 5)pumice,” Sigurdsson says. “That volume is by far the largest volume of any volcanic eruption in life on earth.”
　　
　　Global Cooling
　　But it was the enormous cloud of gas � some 400 million tons of it � released by the eruption that produced “the year without summer.”
　　When the gas reacted with water 6)vapor in the atmosphere, it formed tiny little droplets of 7)sulfuric acid that became suspended in the 8)stratosphere, creating a veil over the Earth, Sigurdsson says.
　　This veil of gas acted like a mirror, bouncing radiation back into space and decreasing the amount of heat that reached the Earth’s surface, causing global cooling, he says.
　　Of course, no one knew that at the time, and few people know about it even now. It wasn’t until the early ’80s, Sigurdsson says, that he caught the Tambora 9)bug. In that decade, researchers taking core samples in Greenland’s ice made an amazing discovery.
　　“You drill down through the ice, and you can count the rings just like in a tree. And people started doing research on the layers, and they found there was a 10)whacking great sulfur concentration at one particular layer: 1816,” Sigurdsson says.
　　“That was first evidence that Tambora had global reach…and that it was unstudied,” he says, adding, “We needed to get much more 11)info on what really happened here.”
　　
　　The Year Without Summer
　　The year after Tambora erupted, Europe was trying to cope with the aftermath of the Napoleonic Wars.
　　There was a mass 12)demobilization of soldiers flooding into the labor market.
　　Patrick Webb, a 13)dean at Tufts University’s Friedman School of Nutrition Science, describes the 14)socio-political climate after the wars.
　　“You had economies disrupted, infrastructure damaged, governments in 15)limbo,” Webb says. “And so the conditions were already ripe for something to go wrong.”
　　And something did go wrong in 1816, known as “the year without summer.” Temperatures dropped, crops failed and people starved.
　　“Hundreds of thousands of people died. People were reduced to eating rats and fighting over roots,” Webb says. “Most of these people were killed by 16)epidemic disease, such as 17)typhus and other things related to starvation. They simply couldn’t find enough food.”
　　In America, New Englanders saw snow well into the summer � the average temperature in July and August was 5 to 10 degrees below normal, according to Webb.
　　
　　Reading the Layers of Earth
　　For more than two decades, Sigurdsson, the volcanologist, has been gathering information from the Indonesian Island. His first trip to the volcano, Tambora, was in 1986, and his most recent trip was just a few months ago. His task is made easier, he says, by the 18)scrupulous record keeping done by the earth itself. The layers of the soil on the island are not unlike the layers of ice in faraway Greenland.
　　“Each layer is like a page in a book. These layers are really a graphic representation of the eruption,” Sigurdsson says. “They are drawing out for us, writing down for us, the history of the volcano. And they don’t lie.”
　　While he was digging, Sigurdsson discovered something else: artifacts and remains carbonized when Tambora erupted. He calls his 19)excavation site “The Lost Kingdom of Tambora” � a find he also refers to as “The Pompeii of the East.”
　　“I have studied deposits in Pompeii and Herculaneum, from the great destruction of Vesuvius in 79 A.D. It’s the same mode of destruction, the same mode of death. But the difference here is that the human remains are much more carbonized � almost entirely carbonized,” Sigurdsson says.
　　“The bones are a piece of 20)charcoal,” he says. That tells scientists that it was a much bigger explosion � with much higher temperatures.
　　The explosion was hot enough to melt glass, and it happened so fast that people living on the island had no chance to escape. The carbonized remains of one woman recovered at the site confirm this.
　　“There is a 21)sarong over her shoulder. The sarong is totally carbonized, just like her bones,” Sigurdsson says. “Her head is resting on the kitchen floor, just caught there instantly and blown over by the flow.”
　　
　　The Lessons of Tambora
　　All the big volcanic eruptions � Tambora, Krakatau, Pinatubo � have ended up cooling the Earth, causing temperatures to drop. And that has some people thinking about 22)replicating the Tambora effect in an effort to slow global warming.
　　“People have proposed that we induce artificial volcanoes by bringing sulfur up into the stratosphere to produce this effect,” Sigurdsson says. But he also warns, “Do you want to counter one 23)pollutant with another one? I don’t think so. But that’s been proposed.”
　　Still, Sigurdsson thinks that lessons from eruptions like Tambora can be applied to models used to study global climate change.
　　Global warming is viewed by many as the most pressing, most dangerous threat. But Sigurdsson warns that 24)catastrophic climate change might come from an unexpected, yet familiar, direction.
　　“Somewhere on the Earth, within the next 1,000 years, there will be a comparable eruption. And we’d better be aware of the consequences,” he says.
　　He notes that another giant volcanic blast would release large amounts of gases, creating interference in the atmosphere that could cause major disruptions in telecommunications and 25)aviation.
　　
　　近200年前，印度尼西亚群岛中部的松巴哇岛上发生了人类史上记载的最大一次火山爆发。
　　这座火山叫坦博拉。罗得岛大学的火山专家哈拉尔德・西戈德森称，这次火山爆发是有文字记载以来最被忽视的一次。
　　坦博拉火山的爆发比喀拉喀托火山要强烈10倍，比维苏威火山或圣海伦火山要强烈100倍以上。近10万人在其波及下丧生。
　　“爆发（的喷发物）冲上43千米高的大气层。这是接近30英里的高度――比今天任何飞机的飞行高度都要高得多――而且以火山灰和浮石形式喷发出的熔岩体积约有100立方千米，”西戈德森说。“这次喷发物的体积是至今火山喷发量最大的。”
　　
　　全球变冷
　　不过，火山爆所发产生的、大约4亿吨的巨大气体云造就了一个“无夏之年”。
　　西戈德森解释说，当这种气体和大气中的水蒸气发生作用，就会形成微小的硫磺酸小液滴；而这些小液滴在同温层悬浮起来，给地球蒙上了一层“面纱”。
　　他说，这层气体“面纱”起着镜子般的作用，把热辐射反射回太空，减少到达地球表面的热量，从而使地球变冷。
　　当然，那时候没有人知道这种“全球变冷效应”，甚至到现在，了解的人仍寥寥无几。西戈德森说，直到20世纪80年代早期，他才迷上了坦博拉火山的研究。在那十年里，研究人员从格陵兰岛的冰层中钻取矿石样本，并发现了一个令人惊叹的事实。
　　“穿过冰层往下钻，（从矿石样本中）你可以数出像树的年轮那样的圈层。人们开始对这些圈层进行研究，他们发现，在1816年这一层中，硫的浓度高得惊人，”西戈德森说。
　　“这是坦博拉火山爆发具有全球变冷效应的第一项证据……而这还没人研究过。”他接着补充说，“我们需要获取更多的信息来研究当时的真实情况。”
　　
　　无夏之年
　　坦博拉火山爆发后的那年，欧洲正在试图从拿破仑战争的疮痍中恢复过来。
　　大批士兵卸甲回家，如潮水般涌入了劳动力市场。
　　塔夫斯大学傅莱曼营养科学学院院长帕崔克・韦伯向我们描述了战后的社会政治环境。
　　“经济秩序被打乱，基础设施破败不堪，政府濒临崩溃，”韦伯说道。“情况糟透了，不对劲的事情即将发生。”
　　而在1816年，不对劲的事情确实发生了――这一年被称为“无夏之年”：温度下降，粮食歉收，人民饥肠辘辘。
　　“数万人死去。人们被迫以田鼠为食，为植物的根茎大打出手，”韦伯说道。“大多数都因罹患诸如伤寒症之类的流行病以及其它与饥荒有关的病症死去。这只是因为他们找不到足够的食物充饥。”
　　在美国，新英格兰人见到了夏日飞霜――据韦伯说，七、八月的平均温度比正常情况下要低5到10（摄氏）度。
　　
　　解读地球圈层
　　二十多年来，火山学家西戈德森一直在印度尼西亚岛采集信息。他第一次踏上坦博拉火山是在1986年，而最近一次旅程仅是数月前。他说，地球自身保留下的、细致入微的记录让他的任务变简单了。火山岛上的土壤层次与远隔千里的格陵兰岛的冰层结构差别不大。
　　 “每一层都像书的一页。这些地层实际上就是火山爆发的图表展示，”西戈德森说。“它们为我们描绘，为我们书写火山的历史，而且它们不会撒谎。”
　　当西戈德森进行深入挖掘时，他发现了另外一些东西：坦博拉火山喷发时碳化了的人工制品和遗骸。他把这座挖掘遗址称作“遗失的坦博拉王国”――并把这个发现称作“东方的庞贝古城”。
　　 “我研究过经历了公元79年维苏威火山爆发大破坏的庞贝和赫库兰尼姆古城沉积物。它们有着相同的毁灭方式，相同的终结方式。不过这里的不同之处在于人类遗骸碳化的程度要严重得多――几乎全被碳化了，”西戈德森说道。
　　 “这些骨头都变成了一片片炭块，”他说。这些遗迹告诉科学家，这次爆发的规模要大得多――爆发温度也高得多。
　　火山喷发产生的热量足以熔化玻璃；而这一切都发生在迅雷不及掩耳之间，以致生活在岛上的人根本没有机会逃生。在遗址上复原的一副碳化了的女性遗骸证明了这个
　　推断。
　　 “她的肩上搭着一条纱笼。这条纱笼和她的骸骨一样，已完全碳化，”西戈德森说。“她的头枕在厨房的地板上，这说明她刚到厨房就被爆炸的滚滚热浪袭倒在地。”
　　
　　坦博拉的启示
　　所有的大型火山爆发――无论是坦博拉火山、喀拉喀托火山、还是皮纳图博火山――最终都造成了地球变冷，温度降低。这种现象让一些人开始猜想：如果“坦博拉效应”可以复制的话，岂不可以减缓全球变暖的趋势？
　　“有人提议说，我们可以通过把硫放入同温层中，制造‘人造火山’，从而降低全球温度，”西戈德森说道。不过，他同时警告：“你想用一种污染物来对付另外一种污染吗？我想，答案是否定的。不过，确实有人
　　提过这种方法。”
　　尽管如此，西戈德森认为，从坦博拉这样的火山爆发中得到的启示可以应用于全球气候变化的研究模型中去。
　　人们都认为全球变暖是人类最紧迫、最危险的威胁。不过，西戈德森提醒说，灾难性的气候变化可能来自意料之外、又被人忽视的类似方面。
　　“在未来1000年内，地球上的某个角落将会发生一场规模可与坦博拉比肩的火山大爆发。我们最好清楚了解它会带来的后果，”他说。
　　他表示，下一次超大型的火山爆发将会释放大量气体，产生大气干扰，继而造成大规模的电信和航空业务中断。