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A million years ago , molten magma explosively burst above the waves .

一百万年前，熔化的岩浆在海波之上爆发性喷发出来。

The optimum depth for their formation is about 120 miles beneath the surface , in the molten mantle .

其形成的最佳深度是在地表之下约120英里，在熔化的地幔曾。

Rock formed from molten matter is known as igneous , and geologists classify igneous rock by its texture .

由熔化的物质凝固形成的岩石称为岩浆岩或火成岩（后者概念更广泛），地质学家按火成岩的结构进行分类。

Once the molten debris coalesced into the moon , the theory goes , its crust solidified over several hundred million years .

进一步的理论说明，一旦熔化的碎片合并到月球上，月球的地壳凝固时间超过了几亿年。

If enough molten fuel gathers this way , a critical mass may be assembled , reigniting the fission reaction .

如果以这种方式熔化的燃料足够多，或许能够组成一个临界质量，重新引发裂变反应。