The oceanic plate is made of denser and heavier rock, so it begins to sink down under the continental plate and into the mantle.

海洋板块是由密度更大、更重的岩石构成的，所以它开始下沉到大陆板块之下，到地幔之中。

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By 2011 scientists aboard a Japanese deep-sea drilling ship called Chikyu hope to start drilling through a thin piece of oceanic crust to reach Earth's mantle.

2011年，科学家们将登上日本一艘名为“地球号”的深海钻井船，他们希望通过钻开一块薄的大洋地壳到达地幔。

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But geophysicists had thought that great subduction-zone earthquakes happened only where younger oceanic crust scrapes its way into the mantle.

但是在此之前，地球物理学者们认为，这种俯冲带大地震仅仅在年轻的海洋地壳挤入地幔处才可能发生。

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