CompuServe Messages

Kamron, >> I have done clay modeling on a globe and the continents fit almost perfectly together in their current shape. The edge of the continents are virtually a vertical break and they fit together now. This cannot be just a coincidence. It appears that the margins have not changed since the separation. How could all this change and additional coast be added and still they fit together? << You're right, it isn't just a coincidence <g>. The jigsaw-puzzle-like fit of the eastern coast of South America with the western coast of Africa is one of the first pieces of evidence that was advanced for continental drift, eighty-odd years ago. I suspect your globe was on too small a scale for you to see how and why the continents aren't "perfect" fits anymore. The eastern margins of NA and SA and the western margins of Europe and Africa haven't changed greatly since the Atlantic formed because there wasn't much happening there to change them. Seafloor spreading is a slow, steady, not-very-disruptive process. The continents are carried along by plate motion. They don't collide with anything, so there's no tectonic forces causing orogenies, volcanic activity, or subduction. To see where things have been _happening_, you have to look to the west of the Americas, and to the east coasts of Asia and Africa, and the northern and eastern coasts of Australia. IOW, places where plates are moving along each other, or are being subducted. The Rocky Mountains formed after the Atlantic opened; I think the Andes did too, as did Japan and all those Pacific islands that have volcanic origins. The rifting in East Africa is so recent that I think there's a chance it's still going on. Jon W.