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Photo of man at irrigation headgate
世纪早期,垦务局(Federal Bureau of Reclamation)的工程师利用水坝及贮水池将干旱的蛇河(Snake River)平原变为肥沃的土地

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?那是发生在19831028日,爱达荷境内的第一高山博拉峰(Borah Peak)在两分钟内长高了约八英吋。而在同一时间,沿着26哩长的洛斯特里弗岭(Lost River Range)奔流的溪水忽然下降了10英呎。您能猜出导致这件事情发生的原因吗?


冰河移动速度缓慢且会磨蚀山脉。现在博拉峰北部山坡上所残留的部分奥托冰河(Otto Glacier)是爱达荷境内唯一的冰河。它及其他的冰河已经在爱达荷境内的高山山脉刨蚀出500多个冰斗(cirques:圆圈的法文字)。当冰河侵蚀山脉并带走大石块,就会导致一个由山脉围成的圆圈,这个圆圈就称做冰斗;浅的冰斗会变成现在的湿草地,而拥有碗状底部的深冰斗也许会成为湖泊。

Have you ever heard of a mountain growing right before your eyes? That's what happened on October, 28, 1983, when Borah Peak, the highest mountain in Idaho, grew about eight inches higher in two minutes. Around the same time, the valley floor along 26 miles of the Lost River Range suddenly lowered 10 feet. Can you guess how this happened?

It was an earthquake that caused these drastic changes. Idaho is a state of dramatic geographic contrasts. It is a geologically active region that includes glaciers, volcanoes and earthquakes, all of which have produced a spectacular but harsh landscape.

Glaciers move very slowly and grind away at mountains. The Otto Glacier is the only remaining glacier in Idaho. Only a small remnant of what it used to be exists on the north slope of Borah Peak. It and other glaciers have created more than 500 cirques (French for "circle") in the high mountains of Idaho. A cirque is formed when glacial erosion removes big blocks of rock from mountains, resulting in a circle surrounded by mountains. Shallow cirques appear as wet meadows today, while the deeper ones with bowl-shaped floors may contain lakes.

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