两次喷发之间可能过去了数百万年。

Millions of years may pass between eruptions.

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一些科学家认为过去大量海洋生物的灭绝，将引起数百万年后地球碳循环上下幅度变大。

Some scientists think that massive ocean extinction events in the past caused Earth's carbon cycle to fluctuate wildly for millions of years afterwards.

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据认为，与地球一样，在过去数百万年里火星也经历了全球气候变化。

Mars, like Earth, is believed to have experienced global climate changes over the past few million years.

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