As a result of a string of remarkable geological discoveries during the past decade, many bewildering features of the earth's surface are being satisfactorily explained for the first time. Most scientists finally agree, for example, that the continentswhich look as if they once fitted together like a giant jigsaw puzzleindeed broke off from one or two immense land masses along volcanically active cracks in the earth's crust known as mid-ocean ridges. Part of this undersea mountain chain, which girdles the earth like stitching on a baseball, has now been identified as the prime...
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