地质学家在石笋上钻孔，使用铀衰变成钍的同位素的方法确定它们的年龄。
In this case the geologists drilled into the stalagmites and estimated their age from the way that uranium decays into an isotope of thorium.
我们脚下深处是地狱般的岩石汤，在温度非常高的地球地幔中，有毒的铀、钍和钾元素的同位素释放出的辐射流不断地对这些岩石汤进行加热，使其保持高温。
Deep underneath your feet is a hellish stone soup, kept hot by a torrent of radiation from poisonous isotopes of uranium, thorium and potassium in the earth's superheated mantle.
壳型花岗岩具较高的铅同位素比值和富铀铅贫钍铅的特点；
The crust granites have higher lead isotope ratios and are richer in uranium lead but poorer in thorium lead.
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