【英语时差8,16】地幔（在线收听）

 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.But over time, form mountain ranges and volcanoes. 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. Scientists talk about the mantle as a kind of weather system. There are cooler and warmer sections of the mantle that are in constant flux with one another, much like gathering storm clouds. These subterranean storms miles below the earth’s surface, though very slow in development, can eventually exert powerful force on the earth’s crust.