For some time now, scientists have understood that the earth's crust is divided into plates that move about at the rate of a few inches a year.
现在科学家们已经搞清楚地壳分为各个板块，而且板块间以每年几英寸的速度移动着。
But over time, form mountain ranges and volcanoes.
但随着时间的推移山脉和火山得以形成。
They have also known that the earth's mantle, the layer between the earth's crust and core, was the major player in the movement of the plates.
他们也已经搞清楚地球的地幔，就是地壳和核心之间的那层是板块运动的主要参与者。
Scientists talk about the mantle as a kind of weather system.
科学家认为地幔是一种天气系统。
There are cooler and warmer sections of the mantle that are in constant flux with one another, much like gathering storm clouds.
地幔部分持续的流动有冷却器和温暖,就像风暴云聚集一样。
These subterranean storms miles below the earth's surface, though very slow in development, can eventually exert powerful force on the earth's crust.
这些地下风暴低于地球表面,虽然发展非常缓慢,最终会对地壳产生强大的力量。
