瀑布是由熔岩和火山物质构成的。

The Cascades are made up of lavas and volcanic materials.

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这里被称为火圈带，一个由剧烈移动的板块和火山组成的半圆形区域，分布在太平洋沿岸。

It's called the Ring of Fire, a semicircle of violently shifting plates and volcanoes that runs along the edges of the Pacific Ocean.

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铱存在于陨石和火山物质中，但在火山物质中同时包含高浓度的镍和铬。

Iridium occurs in meteorites and volcanic material, but in the latter case it is accompanied by elevated levels of nickel and chromium.

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The trouble is, you just don't know when that explosion took place, and since there are several periods in this general area that we're talking about now, in which something big happened, some great change takes place, it turns out different people want to have their explosion at different times.

问题是,你不了解火山爆发的,确切时间以及这种爆发,在这个区域又延续了很多个时期,这些时期发生了许多重大事件和重大变化,结果就是不同人对,火山爆发的时间推测各不相同

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