"从人们开始对地表的特殊岩层进行编目和分类时起，大家就开始期望能够以某种方式利用这些岩层来计算地质年代。
Ever since people had begun to catalog the strata in particular outcrops, there had been the hope that these could somehow be used to calculate geological time.
作为地质学家，我们研究地球表面的沉积层以估算过去地质时期的年代。
As geologists, we examine layers of sediment on the Earth' s surface to approximate the dates of past geologic time periods.
人类造成的突变(以地质时期为尺度衡量)，其证据触目惊心。
Evidence of abrupt change — on a geological time scale — wrought by human hands would seem to be overwhelming.
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