【英语时差8,16】海底扩张理论（在线收听）

Support for Alfred Wegener's ideas did not come until the early nineteen-fifties. American scientists Harry Hess and Robert Dietz said the continents moved as new sea floor was created under the Atlantic Ocean. They said a t hin valley in the Atlantic Ocean was a place where the ocean floor splits.The floor of the Atlantic Ocean is moving away from each side of the split. The movement is very slow -- a few centimeters a year.The moving ocean floor is blocked when it comes up against the edge of a continent. Then it is forced down under the continent, deep into the Earth, where it is melted again. Harry Hess and Robert Dietz said this spreading does not make the Earth bigger. As new ocean floor is created, an equal amount is destroyed. The two scientists also said Alfred Wegener was correct. The continents move as new material from the center of the Earth rises, hardens and pushes older pieces of the Earth away from each other. The continents are moving all the time, although we cannot feel it. 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.