VOA慢速英语:Earth’s Continents and Ocean Floors Are Always Moving

例句：The object is no longer in cyclical motion.
      这物体已不再循环运动。

2.crack vt.vi.(使…)开裂, 破裂

例句：But at last the shells cracked, one after another.
      最后, 蛋壳一个接着一个地裂开了。

3.underwater adj.水面下的;水下使用的;水下进行的

例句：The ship was underwater when they reached her.
      他们赶到那艘船时, 船已沉到水里了。

4.split vt.vi.(使)裂开; (使)破裂

例句：The wood splits easily.
      这木头容易劈开。

      His coat has split open at the seams.
      他的外套在接缝处裂开。

5.tectonic adj.构造的,建筑的