遠(yuǎn)古火山噴發(fā)
古代的火山更具殺傷力，不是因?yàn)樗鼈兏?，而是因?yàn)樗鼈冡尫懦鰜?lái)的二氧化碳更容易把人殺死。
來(lái)自里茲大學(xué)的Paul Wignall正在調(diào)查火山爆發(fā)和大規(guī)模物種滅絕之間的聯(lián)系。不是所有的火山都會(huì)造成大量動(dòng)物死亡。但在過(guò)去的三億年間，巨大的火山巖石的形成都伴隨著大規(guī)模種族滅絕。讓他驚奇的是，遠(yuǎn)古的火山造成的破壞更大。他通過(guò)比較火山釋放出的熔巖的體積與殺死生命的比例計(jì)算這些火山的殺傷效力。他發(fā)現(xiàn)，體積相同的情況下，老遠(yuǎn)古火山要比近期火山的殺傷力大十倍。
例如，發(fā)生在兩億五千年前的二疊紀(jì)物種滅絕就與西伯利亞的火山爆發(fā)發(fā)生在同一時(shí)期。當(dāng)時(shí)的火山巖大約覆蓋了西歐那么大的面積。當(dāng)時(shí)火山釋放出了大約100億噸梯恩梯的二氧化碳，隨之而來(lái)的全球變暖殺死了80%的海洋生物。500萬(wàn)年以后，地球才恢復(fù)到原來(lái)的狀態(tài)。然而，6000年前，火山大規(guī)模爆發(fā)，以及而后的全球變暖并沒(méi)有帶來(lái)種族滅絕。一些動(dòng)物確實(shí)消失了，但幾萬(wàn)年以后，地球又恢復(fù)到以前的水平?！白罱囊淮位鹕奖l(fā)基本上沒(méi)帶來(lái)什么影響?！盬ignall稱(chēng)。他并沒(méi)有將650萬(wàn)年前的恐龍滅絕計(jì)算在內(nèi)，因?yàn)榇蟛糠值目茖W(xué)家認(rèn)為那是有小行星撞擊地球所引起的。他認(rèn)為，遠(yuǎn)古火山之所以殺傷力大是因?yàn)榻诘纳锬軌蚋玫倪m應(yīng)二氧化碳含量上升。
法國(guó)巴黎地理研究所的所長(zhǎng)Vincent Courtillot稱(chēng)Wignall的觀點(diǎn)很具爭(zhēng)議性，并且很難做出這樣的計(jì)算。他指出火山爆發(fā)的殺傷力是由其持續(xù)長(zhǎng)度所決定的。并且很難知道是否大規(guī)模爆發(fā)會(huì)持續(xù)上百萬(wàn)年。他補(bǔ)充道，很難計(jì)算遠(yuǎn)古火山灰噴發(fā)多少火山巖，并且火山巖的數(shù)量也不一定和二氧化碳釋放數(shù)量相一致。
Older Volcanic Eruptions
Volcanoes were more destructive in ancient history, not because they were bigger, but because the carbon dioxide they released wiped out life with greater ease.
Paul Wignall from the University of Leeds was investigating the link between volcanic eruptions and mass extinctions. Not all volcanic eruptions killed off large numbers of animals, but all the mass extinctions over the past 300 million years coincided with huge formations of volcanic rock. To his surprise, the older the massive volcanic eruptions were, the more damage they seemed to do. He calculated the "killing efficiency" for these volcanoes by comparing the proportion of life they killed off with the volume of lava that they produced. He found that size for size, older eruptions were at least 10 times as effective at wiping out life as their more recent rivals.
The Permian extinction, for example, which happened 250 million years ago, is marked by floods of volcanic rock in Siberia that cover an area roughly the size of western Europe. Those volcanoes are thought to have pumped out about 10 gigatonnes of carbon as carbon dioxide. The global warming that followed wiped out 80 per cent of all marine genera at the time, and it took 5 million years for the planet to recover. Yet 60 million years ago, there was another huge amount of volcanic activity and global warming but no mass extinction. Some animals did disappear but things returned to normal within ten thousands of years. "The most recent ones hardly have an effect at all," Wignall says. He ignored the extinction which wiped out the dinosaurs 65 million years ago, because many scientists believe it was primarily caused by the impact of an asteroid. He thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO2.
Vincent Courtillot, director of the Paris Geophysical Institute in France, says that Wignall's idea is provocative. But he says it is incredibly hard to do these sorts of calculations. He points out that the killing power of volcanic eruptions depends on how long they lasted. And it is impossible to tell whether the huge blasts lasted for thousands or millions of years. He also adds that it is difficult to estimate how much lava prehistoric volcanoes produced, and that lava volume may not necessarily correspond to carbon dioxide emissions.
古代的火山更具殺傷力，不是因?yàn)樗鼈兏?，而是因?yàn)樗鼈冡尫懦鰜?lái)的二氧化碳更容易把人殺死。
來(lái)自里茲大學(xué)的Paul Wignall正在調(diào)查火山爆發(fā)和大規(guī)模物種滅絕之間的聯(lián)系。不是所有的火山都會(huì)造成大量動(dòng)物死亡。但在過(guò)去的三億年間，巨大的火山巖石的形成都伴隨著大規(guī)模種族滅絕。讓他驚奇的是，遠(yuǎn)古的火山造成的破壞更大。他通過(guò)比較火山釋放出的熔巖的體積與殺死生命的比例計(jì)算這些火山的殺傷效力。他發(fā)現(xiàn)，體積相同的情況下，老遠(yuǎn)古火山要比近期火山的殺傷力大十倍。
例如，發(fā)生在兩億五千年前的二疊紀(jì)物種滅絕就與西伯利亞的火山爆發(fā)發(fā)生在同一時(shí)期。當(dāng)時(shí)的火山巖大約覆蓋了西歐那么大的面積。當(dāng)時(shí)火山釋放出了大約100億噸梯恩梯的二氧化碳，隨之而來(lái)的全球變暖殺死了80%的海洋生物。500萬(wàn)年以后，地球才恢復(fù)到原來(lái)的狀態(tài)。然而，6000年前，火山大規(guī)模爆發(fā)，以及而后的全球變暖并沒(méi)有帶來(lái)種族滅絕。一些動(dòng)物確實(shí)消失了，但幾萬(wàn)年以后，地球又恢復(fù)到以前的水平?！白罱囊淮位鹕奖l(fā)基本上沒(méi)帶來(lái)什么影響?！盬ignall稱(chēng)。他并沒(méi)有將650萬(wàn)年前的恐龍滅絕計(jì)算在內(nèi)，因?yàn)榇蟛糠值目茖W(xué)家認(rèn)為那是有小行星撞擊地球所引起的。他認(rèn)為，遠(yuǎn)古火山之所以殺傷力大是因?yàn)榻诘纳锬軌蚋玫倪m應(yīng)二氧化碳含量上升。
法國(guó)巴黎地理研究所的所長(zhǎng)Vincent Courtillot稱(chēng)Wignall的觀點(diǎn)很具爭(zhēng)議性，并且很難做出這樣的計(jì)算。他指出火山爆發(fā)的殺傷力是由其持續(xù)長(zhǎng)度所決定的。并且很難知道是否大規(guī)模爆發(fā)會(huì)持續(xù)上百萬(wàn)年。他補(bǔ)充道，很難計(jì)算遠(yuǎn)古火山灰噴發(fā)多少火山巖，并且火山巖的數(shù)量也不一定和二氧化碳釋放數(shù)量相一致。
Older Volcanic Eruptions
Volcanoes were more destructive in ancient history, not because they were bigger, but because the carbon dioxide they released wiped out life with greater ease.
Paul Wignall from the University of Leeds was investigating the link between volcanic eruptions and mass extinctions. Not all volcanic eruptions killed off large numbers of animals, but all the mass extinctions over the past 300 million years coincided with huge formations of volcanic rock. To his surprise, the older the massive volcanic eruptions were, the more damage they seemed to do. He calculated the "killing efficiency" for these volcanoes by comparing the proportion of life they killed off with the volume of lava that they produced. He found that size for size, older eruptions were at least 10 times as effective at wiping out life as their more recent rivals.
The Permian extinction, for example, which happened 250 million years ago, is marked by floods of volcanic rock in Siberia that cover an area roughly the size of western Europe. Those volcanoes are thought to have pumped out about 10 gigatonnes of carbon as carbon dioxide. The global warming that followed wiped out 80 per cent of all marine genera at the time, and it took 5 million years for the planet to recover. Yet 60 million years ago, there was another huge amount of volcanic activity and global warming but no mass extinction. Some animals did disappear but things returned to normal within ten thousands of years. "The most recent ones hardly have an effect at all," Wignall says. He ignored the extinction which wiped out the dinosaurs 65 million years ago, because many scientists believe it was primarily caused by the impact of an asteroid. He thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO2.
Vincent Courtillot, director of the Paris Geophysical Institute in France, says that Wignall's idea is provocative. But he says it is incredibly hard to do these sorts of calculations. He points out that the killing power of volcanic eruptions depends on how long they lasted. And it is impossible to tell whether the huge blasts lasted for thousands or millions of years. He also adds that it is difficult to estimate how much lava prehistoric volcanoes produced, and that lava volume may not necessarily correspond to carbon dioxide emissions.