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These are volcanoes so explosive that they burst open in a single mighty rupture, leaving behind a vast subsided pit, the caldera (from a Latin word for cauldron). Yellowstone obviously was of this second type, but Christiansen couldn't find the caldera anywhere.
這種火山的威力如此之大，它們一下子破土而出，留下一個沉降式大坑，即破火山口（源自拉丁語，意思是大鍋）。黃石火山顯然屬于第二種，但克里斯琴森哪里也找不到那個破火山口。
By coincidence just at this time NASA decided to test some new high-altitude cameras by taking photographs of Yellowstone, copies of which some thoughtful official passed on to the park authorities on the assumption that they might make a nice blow-up for one of the visitors' centers. As soon as Christiansen saw the photos he realized why he had failed to spot the caldera: virtually the whole park—2.2 million acres—was caldera. The explosion had left a crater more than forty miles across—much too huge to be perceived from anywhere at ground level. At some time in the past Yellowstone must have blown up with a violence far beyond the scale of anything known to humans.
恰好在這個時候，美國國家航空和航天局決定拍攝黃石公園的照片，測試一下某些新型的高空照相機。一位考慮周到的官員把其中的有些照片交給了公園當局，認為它們可以掛在某個游客中心?？死锼骨偕豢吹竭@些照片，馬上意識到他沒有找到破火山口的原因：實際上，整個公園——9000平方公里——就是破火山口?；鹕奖l(fā)留下了一個直徑將近65公里的大坑——大得從地面上的任何角度都看不明白。過去某個時刻，黃石公園可能被炸得七零八落，威力之大遠遠超過了人類已知的任何等級。
Yellowstone, it turns out, is a supervolcano. It sits on top of an enormous hot spot, a reservoir of molten rock that rises from at least 125 miles down in the Earth. The heat from the hot spot is what powers all of Yellowstone's vents, geysers, hot springs, and popping mud pots. Beneath the surface is a magma chamber that is about forty-five miles across—roughly the same dimensions as the park—and about eight miles thick at its thickest point.
結(jié)果發(fā)現(xiàn)，黃石公園是一座超級火山。它坐落在一個巨大的熱點——一個熔巖儲藏所——之上。這個儲藏所下達地球至少200公里深處，上至接近地面的地方，形成了一根所謂的超級熱柱。熱點的熱量為黃石公園里所有的噴氣口、間歇泉、溫泉和冒泡的泥坑提供了動力。地面以下是個巖漿房，直徑約為72公里——大致相當于公園的大小，最厚的地方達13公里左右。
