Alfred Wegener said the mountains and fossils were evidence that all the land on Earth was united at some time in the distant past.
Alfred WegenerVOICE TWO:
Wegener also noted differences between the continents and the ocean floor. He said the oceans were more than just low places that had filled with water. Even if the water was removed, he said, a person would still see differences between the continents and the ocean floor.
Also, the continents and the ocean floor are not made of the same kind of rock. The continents are made of a granite-like rock, a mixture of silicon and aluminum. The ocean floor is basalt rock, a mixture of silicon and magnesium. Mister Wegener said the lighter continental rock floated up through the heavier basalt rock of the ocean floor.
VOICE ONE:
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 thin valley in the Atlantic Ocean was a place where the ocean floor splits. They said hot melted material flows up from deep inside the Earth through the split. As the hot material reaches the ocean floor, it spreads out, cools and hardens. It becomes new ocean floor.
The two scientists proposed that 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.
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2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25