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1·This is part of the system of mid-ocean ridges that form as the tectonic plates of the Earth's crust move apart-a process known as sea floor spreading.

印度洋脊是中大洋脊的一部分，中大洋脊是地壳分离的地球板块形成的。这一形成过程被称为海底扩张。

2·They called their theory sea floor spreading. the theory explains that as the sea floor spreads, the tectonic plates are pushed and pulled in different directions.

他们把他们的理论叫做“海底扩张”。这个理论解释了，随着海底扩张，板块在不同的方向上被推拉。