A部分

Volcanoes are the ultimate earth-moving machinery. A violent eruption can blow the top few kilometres off a mountain, scatter fine ash practically all over the globe and hurl rock fragments into the stratosphere to darken the skies a continent away.

But the classic eruption – cone-shaped mountain, big bang, mushroom cloud and surges of molten lava – is only a tiny part of a global story. Vulcanism, the name given to volcanic processes, really has shaped the world. Eruptions have rifted continents, raised mountain chains, constructed islands and shaped the topography of the earth. The entire ocean floor has a basement of volcanic basalt.

Volcanoes have not only made the continents, they are also thought to have made the world’s first stable atmosphere and provided all the water for the oceans, rivers and ice-caps. There are now about 600 active volcanoes. Every year they add two or three cubic kilometres of rock to the continents. Imagine a similar number of volcanoes smoking away for the last 3,500 million years. That is enough rock to explain the continental crust.

What comes out of volcanic craters is mostly gas. More than 90% of this gas is water vapour from the deep earth: enough to explain, over 3,500 million years, the water in the oceans. The rest of the gas is nitrogen, carbon dioxide, sulphur dioxide, methane, ammonia and hydrogen. The quantity of these gases, again multiplied over 3,500 million years, is enough to explain the mass of the world’s atmosphere. We are alive because volcanoes provided the soil, air and water we need.

A部分

火山是终极的地球移动机器。猛烈的喷发可以将山顶的几公里吹掉，将细灰岩散布至全球，并将岩石碎片抛向平流层，使遥远的大陆上的天空变暗。

但典型的喷发——锥形山、大爆炸、蘑菇云和熔岩涌动——只是全球故事的一小部分。火山作用，即火山过程，真正塑造了世界。喷发造成了大陆断裂、山脉抬升、岛屿构建和地球地形的形成。整个海底都有火山玄武岩构成的底层。

火山不仅创造了大陆，还被认为创造了世界上第一个稳定的大气层，并提供了我们所需的土壤、空气和水。现在大约有600座活火山。每年它们为大陆增加两到三立方千米的岩石。想象一下，在过去的35亿年里，同样数量的火山持续喷放。足够解释大陆地壳的岩石组成。

火山口喷发出的物质主要是气体。超过90%的气体是来自地球深处的水蒸汽：足以解释35亿年来海洋中的水。其余的气体是氮气、二氧化碳、二氧化硫、甲烷、氨和氢。这些气体的数量再乘以35亿年，足以解释世界大气层的质量。我们之所以能够生存，是因为火山提供了我们所需的土壤、空气和水。