The crust eventually becomes a rigid roof, forming a lava tube.
地壳最终成为一个僵化的屋顶，形成了熔岩管。
Because there were roof collapses at several places along the lava tube that formed Indian Tunnel, it is possible to enter on one end and come out the other side.
因为有沿熔岩隧道管，形成了印度一些地方的屋顶坍塌，有可能进入一端出来的另一面。
This forces water through a tube formed by the tongue pressed against a groove in the roof of the mouth.
这迫使水流过一条由舌头压在上颚的沟槽部分形成的管道中。
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