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Most of the time, volcanoes look like other mountains:
大多數(shù)時候，火山看起來和其他的山體沒有兩樣：
solid,serene, capped with snow–a nice place to go camping.
固體，平靜，被積雪覆蓋-露營的不錯選擇。
Unless, of course, it happens to explode and pour molten lava all over your campsite!
除非，當然，它突然噴發(fā)，熔漿覆蓋你的營地。
Wouldn't itbe nice if we could predict when a volcano was about to erupt?
如果我們能夠預測火山什么時候會噴發(fā)，是不是更好呢？
Scientists have recently taken a big step closer toward doing just this.
科學家們最近在此領域的研究取得了進展。
Let's look inside a volcano.
讓我們一起來看看火山的內部結構吧！
At the center is a reservoir of molten rock, known as magma.
中心是一個熔巖的“液態(tài)區(qū)”，叫巖漿。
This magma is very hot, and under a lot of pressure.
巖漿溫度很高，并且處于一定的壓力之下。
When rainwater seeps into cracks in themountain, the magma turns it into steam and forces it out again.
當雨水滲入山縫后，巖漿將其蒸發(fā)為水蒸汽，又讓它排放出來。
The magma also vents awayhot gasses through these same cracks.
巖漿也同樣通過這些山縫散發(fā)一些熱氣。
This is a volcano's normal state.
這是一座火山的正常狀態(tài)。
When gasses and steam vent from a volcano's cracks, it'sprobably not about to erupt.
當氣體和蒸汽可以從火山的裂縫排放時，它可能并不會噴發(fā)。
Sometimes, however, the top layer of magma can cool, and form ahard crust over the rest of the molten rock.
然而，有時頂層的巖漿會冷卻，并在外部形成一個堅硬的殼。
When this happens, rainwater is able to collect in thecracks without evaporating, and this water captures a lot of gasses that would ordinarily vent fromthe magma.
這時，雨水聚集在巖縫中，不能蒸發(fā)。這些雨水阻止了巖漿熱氣的排放。
Scientific instruments inside the volcano's cracks record a sudden drop in temperature, and much less volcanic gas.
在山縫中的科學儀器記錄到了溫度的陡然下降，和火山氣體的減少。
This is a warning sign for an imminent eruption.
這是即將噴發(fā)的一個預兆。冷卻的巖漿殼讓內部的液體壓力增大。
That cool magmaseal allows pressure to build upinside the liquid magma, much like your thumb over the top of a shaken soda bottle will seal inthe pressure.
就像把你的拇指放在被搖過的蘇打水瓶口上，使其密封，增加內部壓力。
When that magmaseal gives way it's like taking your thumb off the top of the bottle, and you don't want to be camping on the volcano when that happens!
巖漿上部的密封殼被沖開時，就像你的拇指從蘇打水瓶上拿開的時候一樣，在這種情況下，你就不會想要在火山上露營了。
